Paul noticed that the conversion of the death reporting introduced a race
where the outgoing cpu might be delayed after waking the controll processor,
so it might not be able to call rcu_report_dead() before being physically
removed, leading to RCU stalls.
We cant call complete after rcu_report_dead(), so instead of going back to
busy polling, simply issue a function call to do the completion.
Fixes: 27d50c7eeb "rcu: Make CPU_DYING_IDLE an explicit call"
Reported-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/20160302201127.GA23440@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Another representative use case of time sync and the correlated
clocksource (in addition to PTP noted above) is PTP synchronized
audio.
In a streaming application, as an example, samples will be sent and/or
received by multiple devices with a presentation time that is in terms
of the PTP master clock. Synchronizing the audio output on these
devices requires correlating the audio clock with the PTP master
clock. The more precise this correlation is, the better the audio
quality (i.e. out of sync audio sounds bad).
From an application standpoint, to correlate the PTP master clock with
the audio device clock, the system clock is used as a intermediate
timebase. The transforms such an application would perform are:
System Clock <-> Audio clock
System Clock <-> Network Device Clock [<-> PTP Master Clock]
Modern Intel platforms can perform a more accurate cross timestamp in
hardware (ART,audio device clock). The audio driver requires
ART->system time transforms -- the same as required for the network
driver. These platforms offload audio processing (including
cross-timestamps) to a DSP which to ensure uninterrupted audio
processing, communicates and response to the host only once every
millsecond. As a result is takes up to a millisecond for the DSP to
receive a request, the request is processed by the DSP, the audio
output hardware is polled for completion, the result is copied into
shared memory, and the host is notified. All of these operation occur
on a millisecond cadence. This transaction requires about 2 ms, but
under heavier workloads it may take up to 4 ms.
Adding a history allows these slow devices the option of providing an
ART value outside of the current interval. In this case, the callback
provided is an accessor function for the previously obtained counter
value. If get_system_device_crosststamp() receives a counter value
previous to cycle_last, it consults the history provided as an
argument in history_ref and interpolates the realtime and monotonic
raw system time using the provided counter value. If there are any
clock discontinuities, e.g. from calling settimeofday(), the monotonic
raw time is interpolated in the usual way, but the realtime clock time
is adjusted by scaling the monotonic raw adjustment.
When an accessor function is used a history argument *must* be
provided. The history is initialized using ktime_get_snapshot() and
must be called before the counter values are read.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Fixed up cycles_t/cycle_t type confusion]
Signed-off-by: John Stultz <john.stultz@linaro.org>
ACKNOWLEDGMENT: cross timestamp code was developed by Thomas Gleixner
<tglx@linutronix.de>. It has changed considerably and any mistakes are
mine.
The precision with which events on multiple networked systems can be
synchronized using, as an example, PTP (IEEE 1588, 802.1AS) is limited
by the precision of the cross timestamps between the system clock and
the device (timestamp) clock. Precision here is the degree of
simultaneity when capturing the cross timestamp.
Currently the PTP cross timestamp is captured in software using the
PTP device driver ioctl PTP_SYS_OFFSET. Reads of the device clock are
interleaved with reads of the realtime clock. At best, the precision
of this cross timestamp is on the order of several microseconds due to
software latencies. Sub-microsecond precision is required for
industrial control and some media applications. To achieve this level
of precision hardware supported cross timestamping is needed.
The function get_device_system_crosstimestamp() allows device drivers
to return a cross timestamp with system time properly scaled to
nanoseconds. The realtime value is needed to discipline that clock
using PTP and the monotonic raw value is used for applications that
don't require a "real" time, but need an unadjusted clock time. The
get_device_system_crosstimestamp() code calls back into the driver to
ensure that the system counter is within the current timekeeping
update interval.
Modern Intel hardware provides an Always Running Timer (ART) which is
exactly related to TSC through a known frequency ratio. The ART is
routed to devices on the system and is used to precisely and
simultaneously capture the device clock with the ART.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Reworked to remove extra structures and simplify calling]
Signed-off-by: John Stultz <john.stultz@linaro.org>
The code in ktime_get_snapshot() is a superset of the code in
ktime_get_raw_and_real() code. Further, ktime_get_raw_and_real() is
called only by the PPS code, pps_get_ts(). Consolidate the
pps_get_ts() code into a single function calling ktime_get_snapshot()
and eliminate ktime_get_raw_and_real(). A side effect of this is that
the raw and real results of pps_get_ts() correspond to exactly the
same clock cycle. Previously these values represented separate reads
of the system clock.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
In the current timekeeping code there isn't any interface to
atomically capture the current relationship between the system counter
and system time. ktime_get_snapshot() returns this triple (counter,
monotonic raw, realtime) in the system_time_snapshot struct.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
[jstultz: Moved structure definitions around to clean things up,
fixed cycles_t/cycle_t confusion.]
Signed-off-by: John Stultz <john.stultz@linaro.org>
The timekeeping code does not currently provide a way to translate
externally provided clocksource cycles to system time. The cycle count
is always provided by the result clocksource read() method internal to
the timekeeping code. The added function timekeeping_cycles_to_ns()
calculated a nanosecond value from a cycle count that can be added to
tk_read_base.base value yielding the current system time. This allows
clocksource cycle values external to the timekeeping code to provide a
cycle count that can be transformed to system time.
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: kevin.b.stanton@intel.com
Cc: kevin.j.clarke@intel.com
Cc: hpa@zytor.com
Cc: jeffrey.t.kirsher@intel.com
Cc: netdev@vger.kernel.org
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Christopher S. Hall <christopher.s.hall@intel.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Instead of checking sched_clock_stable from the nohz subsystem to verify
its tick dependency, migrate it to the new mask in order to include it
to the all-in-one check.
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Instead of providing asynchronous checks for the nohz subsystem to verify
posix cpu timers tick dependency, migrate the latter to the new mask.
In order to keep track of the running timers and expose the tick
dependency accordingly, we must probe the timers queuing and dequeuing
on threads and process lists.
Unfortunately it implies both task and signal level dependencies. We
should be able to further optimize this and merge all that on the task
level dependency, at the cost of a bit of complexity and may be overhead.
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Instead of providing asynchronous checks for the nohz subsystem to verify
sched tick dependency, migrate sched to the new mask.
Everytime a task is enqueued or dequeued, we evaluate the state of the
tick dependency on top of the policy of the tasks in the runqueue, by
order of priority:
SCHED_DEADLINE: Need the tick in order to periodically check for runtime
SCHED_FIFO : Don't need the tick (no round-robin)
SCHED_RR : Need the tick if more than 1 task of the same priority
for round robin (simplified with checking if more than
one SCHED_RR task no matter what priority).
SCHED_NORMAL : Need the tick if more than 1 task for round-robin.
We could optimize that further with one flag per sched policy on the tick
dependency mask and perform only the checks relevant to the policy
concerned by an enqueue/dequeue operation.
Since the checks aren't based on the current task anymore, we could get
rid of the task switch hook but it's still needed for posix cpu
timers.
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
In order to evaluate the scheduler tick dependency without probing
context switches, we need to know how much SCHED_RR and SCHED_FIFO tasks
are enqueued as those policies don't have the same preemption
requirements.
To prepare for that, let's account SCHED_RR tasks, we'll be able to
deduce SCHED_FIFO tasks as well from it and the total RT tasks in the
runqueue.
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Instead of providing asynchronous checks for the nohz subsystem to verify
perf event tick dependency, migrate perf to the new mask.
Perf needs the tick for two situations:
1) Freq events. We could set the tick dependency when those are
installed on a CPU context. But setting a global dependency on top of
the global freq events accounting is much easier. If people want that
to be optimized, we can still refine that on the per-CPU tick dependency
level. This patch dooesn't change the current behaviour anyway.
2) Throttled events: this is a per-cpu dependency.
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
The tick dependency is evaluated on every IRQ and context switch. This
consists is a batch of checks which determine whether it is safe to
stop the tick or not. These checks are often split in many details:
posix cpu timers, scheduler, sched clock, perf events.... each of which
are made of smaller details: posix cpu timer involves checking process
wide timers then thread wide timers. Perf involves checking freq events
then more per cpu details.
Checking these informations asynchronously every time we update the full
dynticks state bring avoidable overhead and a messy layout.
Let's introduce instead tick dependency masks: one for system wide
dependency (unstable sched clock, freq based perf events), one for CPU
wide dependency (sched, throttling perf events), and task/signal level
dependencies (posix cpu timers). The subsystems are responsible
for setting and clearing their dependency through a set of APIs that will
take care of concurrent dependency mask modifications and kick targets
to restart the relevant CPU tick whenever needed.
This new dependency engine stays beside the old one until all subsystems
having a tick dependency are converted to it.
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Make the RCU CPU_DYING_IDLE callback an explicit function call, so it gets
invoked at the proper place.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.870167933@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Kill the busy spinning on the control side and just wait for the hotplugged
cpu to tell that it reached the dead state.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.776157858@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Let the upcoming cpu kick the hotplug thread and let itself complete the
bringup. That way the controll side can just wait for the completion or later
when we made the hotplug machinery async not care at all.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.697655464@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Let the hotplugged cpu invoke the setup/teardown callbacks
(CPU_ONLINE/CPU_DOWN_PREPARE) itself.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.536364371@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
In order to let the hotplugged cpu take care of the setup/teardown, we need a
seperate hotplug thread.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.454541272@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
We need that for running callbacks on the AP and the BP.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.374946234@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Handle the smpboot threads in the state machine.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.295777684@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Move the scheduler cpu online notifier part to the hotplug core. This is
anyway the highest priority callback and we need that functionality right now
for the next changes.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.200791046@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Implement function which allow to setup/remove hotplug state callbacks.
The default behaviour for setup is to call the startup function for this state
for (or on) all cpus which have a hotplug state >= the installed state.
The default behaviour for removal is to call the teardown function for this
state for (or on) all cpus which have a hotplug state >= the installed state.
This includes rollback to the previous state in case of failure.
A special state is CPUHP_ONLINE_DYN. Its for dynamically registering a hotplug
callback pair. This is for drivers which have no dependencies to avoid that we
need to allocate CPUHP states for each of them
For both setup and remove helper functions are provided, which prevent the
core to issue the callbacks. This simplifies the conversion of existing
hotplug notifiers.
[ Dynamic registering implemented by Sebastian Siewior ]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.103464877@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Make it possible to write a target state to the per cpu state file, so we can
switch between states.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182341.022814799@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add a sysfs interface so we can actually see in which state the cpus are in.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.942257522@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
We want to be able to bringup/teardown the cpu to a particular state. Add a
target argument to _cpu_up/down.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.862113133@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Move the functions which need to run on the hotplugged processor into
a state machine array and let the code iterate through these functions.
In a later state, this will grow synchronization points between the
control processor and the hotplugged processor, so we can move the
various architecture implementations of the synchronizations to the
core.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.770651526@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Move the split out steps into a callback array and let the cpu_up/down
code iterate through the array functions. For now most of the
callbacks are asymmetric to resemble the current hotplug maze.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.671816690@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Split cpu_down in separate functions in preparation for state machine
conversion.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.511796562@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Split out into separate functions, so we can convert it to a state machine.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.429389195@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
There are only a few callbacks which really care about FROZEN
vs. !FROZEN. No need to have extra states for this.
Publish the frozen state in an extra variable which is updated under
the hotplug lock and let the users interested deal with it w/o
imposing that extra state checks on everyone.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel <riel@redhat.com>
Cc: Rafael Wysocki <rafael.j.wysocki@intel.com>
Cc: "Srivatsa S. Bhat" <srivatsa@mit.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: http://lkml.kernel.org/r/20160226182340.334912357@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Some tracepoint have multiple fields with the same name, "nr", the first
one is a unique syscall ID, the other is a syscall argument:
# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_io_getevents/format
name: sys_enter_io_getevents
ID: 747
format:
field:unsigned short common_type; offset:0; size:2; signed:0;
field:unsigned char common_flags; offset:2; size:1; signed:0;
field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
field:int common_pid; offset:4; size:4; signed:1;
field:int nr; offset:8; size:4; signed:1;
field:aio_context_t ctx_id; offset:16; size:8; signed:0;
field:long min_nr; offset:24; size:8; signed:0;
field:long nr; offset:32; size:8; signed:0;
field:struct io_event * events; offset:40; size:8; signed:0;
field:struct timespec * timeout; offset:48; size:8; signed:0;
print fmt: "ctx_id: 0x%08lx, min_nr: 0x%08lx, nr: 0x%08lx, events: 0x%08lx, timeout: 0x%08lx", ((unsigned long)(REC->ctx_id)), ((unsigned long)(REC->min_nr)), ((unsigned long)(REC->nr)), ((unsigned long)(REC->events)), ((unsigned long)(REC->timeout))
#
Fix it by renaming the "/format" common tracepoint field "nr" to "__syscall_nr".
Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
[ Do not rename the struct member, just the '/format' field name ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160226132301.3ae065a4@gandalf.local.home
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Add detection for chain_key collision under CONFIG_DEBUG_LOCKDEP.
When a collision is detected the problem is reported and all lock
debugging is turned off.
Tested using liblockdep and the added tests before and after
applying the fix, confirming both that the code added for the
detection correctly reports the problem and that the fix actually
fixes it.
Tested tweaking lockdep to generate false collisions and
verified that the problem is reported and that lock debugging is
turned off.
Also tested with lockdep's test suite after applying the patch:
[ 0.000000] Good, all 253 testcases passed! |
Signed-off-by: Alfredo Alvarez Fernandez <alfredoalvarezernandez@gmail.com>
Cc: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: sasha.levin@oracle.com
Link: http://lkml.kernel.org/r/1455864533-7536-4-git-send-email-alfredoalvarezernandez@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The chain_key hashing macro iterate_chain_key(key1, key2) does not
generate a new different value if both key1 and key2 are 0. In that
case the generated value is again 0. This can lead to collisions which
can result in lockdep not detecting deadlocks or circular
dependencies.
Avoid the problem by using class_idx (1-based) instead of class id
(0-based) as an input for the hashing macro 'key2' in
iterate_chain_key(key1, key2).
The use of class id created collisions in cases like the following:
1.- Consider an initial state in which no class has been acquired yet.
Under these circumstances an AA deadlock will not be detected by
lockdep:
lock [key1,key2]->new key (key1=old chain_key, key2=id)
--------------------------
A [0,0]->0
A [0,0]->0 (collision)
The newly generated chain_key collides with the one used before and as
a result the check for a deadlock is skipped
A simple test using liblockdep and a pthread mutex confirms the
problem: (omitting stack traces)
new class 0xe15038: 0x7ffc64950f20
acquire class [0xe15038] 0x7ffc64950f20
acquire class [0xe15038] 0x7ffc64950f20
hash chain already cached, key: 0000000000000000 tail class:
[0xe15038] 0x7ffc64950f20
2.- Consider an ABBA in 2 different tasks and no class yet acquired.
T1 [key1,key2]->new key T2[key1,key2]->new key
-- --
A [0,0]->0
B [0,1]->1
B [0,1]->1 (collision)
A
In this case the collision prevents lockdep from creating the new
dependency A->B. This in turn results in lockdep not detecting the
circular dependency when T2 acquires A.
Signed-off-by: Alfredo Alvarez Fernandez <alfredoalvarezernandez@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: sasha.levin@oracle.com
Link: http://lkml.kernel.org/r/1455147212-2389-4-git-send-email-alfredoalvarezernandez@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Make use of wake-queues and enable the wakeup to occur after releasing the
wait_lock. This is similar to what we do with rtmutex top waiter,
slightly shortening the critical region and allow other waiters to
acquire the wait_lock sooner. In low contention cases it can also help
the recently woken waiter to find the wait_lock available (fastpath)
when it continues execution.
Reviewed-by: Waiman Long <Waiman.Long@hpe.com>
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ding Tianhong <dingtianhong@huawei.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul E. McKenney <paulmck@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Waiman Long <waiman.long@hpe.com>
Cc: Will Deacon <Will.Deacon@arm.com>
Link: http://lkml.kernel.org/r/20160125022343.GA3322@linux-uzut.site
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch enables the tracking of the number of slowpath locking
operations performed. This can be used to compare against the number
of lock stealing operations to see what percentage of locks are stolen
versus acquired via the regular slowpath.
Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Douglas Hatch <doug.hatch@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott J Norton <scott.norton@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1449778666-13593-2-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The newly introduced smp_cond_acquire() was used to replace the
slowpath lock acquisition loop. Similarly, the new function can also
be applied to the pending bit locking loop. This patch uses the new
function in that loop.
Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Douglas Hatch <doug.hatch@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott J Norton <scott.norton@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1449778666-13593-1-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch moves the lock stealing count tracking code into
pv_queued_spin_steal_lock() instead of via a jacket function simplifying
the code.
Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Douglas Hatch <doug.hatch@hpe.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Scott J Norton <scott.norton@hpe.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1449778666-13593-3-git-send-email-Waiman.Long@hpe.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Similar to commit b4b29f9485 ("locking/osq: Fix ordering of node
initialisation in osq_lock") the use of xchg_acquire() is
fundamentally broken with MCS like constructs.
Furthermore, it turns out we rely on the global transitivity of this
operation because the unlock path observes the pointer with a
READ_ONCE(), not an smp_load_acquire().
This is non-critical because the MCS code isn't actually used and
mostly serves as documentation, a stepping stone to the more complex
things we've build on top of the idea.
Reported-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Fixes: 3552a07a9c ("locking/mcs: Use acquire/release semantics")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
if (A || B) {
} else if (A && !B) {
}
If A we'll take the first branch, if !A we will not satisfy the second.
Therefore the second branch will never be taken.
Reported-by: luca abeni <luca.abeni@unitn.it>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160225140149.GK6357@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The preempt_disable() invokes preempt_count_add() which saves the caller
in ->preempt_disable_ip. It uses CALLER_ADDR1 which does not look for
its caller but for the parent of the caller. Which means we get the correct
caller for something like spin_lock() unless the architectures inlines
those invocations. It is always wrong for preempt_disable() or
local_bh_disable().
This patch makes the function get_lock_parent_ip() which tries
CALLER_ADDR0,1,2 if the former is a locking function.
This seems to record the preempt_disable() caller properly for
preempt_disable() itself as well as for get_cpu_var() or
local_bh_disable().
Steven asked for the get_parent_ip() -> get_lock_parent_ip() rename.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160226135456.GB18244@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When profiling syscall overhead on nohz-full kernels,
after removing __acct_update_integrals() from the profile,
native_sched_clock() remains as the top CPU user. This can be
reduced by moving VIRT_CPU_ACCOUNTING_GEN to jiffy granularity.
This will reduce timing accuracy on nohz_full CPUs to jiffy
based sampling, just like on normal CPUs. It results in
totally removing native_sched_clock from the profile, and
significantly speeding up the syscall entry and exit path,
as well as irq entry and exit, and KVM guest entry & exit.
Additionally, only call the more expensive functions (and
advance the seqlock) when jiffies actually changed.
This code relies on another CPU advancing jiffies when the
system is busy. On a nohz_full system, this is done by a
housekeeping CPU.
A microbenchmark calling an invalid syscall number 10 million
times in a row speeds up an additional 30% over the numbers
with just the previous patches, for a total speedup of about
40% over 4.4 and 4.5-rc1.
Run times for the microbenchmark:
4.4 3.8 seconds
4.5-rc1 3.7 seconds
4.5-rc1 + first patch 3.3 seconds
4.5-rc1 + first 3 patches 3.1 seconds
4.5-rc1 + all patches 2.3 seconds
A non-NOHZ_FULL cpu (not the housekeeping CPU):
all kernels 1.86 seconds
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: clark@redhat.com
Cc: eric.dumazet@gmail.com
Cc: fweisbec@gmail.com
Cc: luto@amacapital.net
Link: http://lkml.kernel.org/r/1455152907-18495-5-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
It looks like all the call paths that lead to __acct_update_integrals()
already have irqs disabled, and __acct_update_integrals() does not need
to disable irqs itself.
This is very convenient since about half the CPU time left in this
function was spent in local_irq_save alone.
Performance of a microbenchmark that calls an invalid syscall
ten million times in a row on a nohz_full CPU improves 21% vs.
4.5-rc1 with both the removal of divisions from __acct_update_integrals()
and this patch, with runtime dropping from 3.7 to 2.9 seconds.
With these patches applied, the highest remaining cpu user in
the trace is native_sched_clock, which is addressed in the next
patch.
For testing purposes I stuck a WARN_ON(!irqs_disabled()) test
in __acct_update_integrals(). It did not trigger.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: clark@redhat.com
Cc: eric.dumazet@gmail.com
Cc: fweisbec@gmail.com
Cc: luto@amacapital.net
Link: http://lkml.kernel.org/r/1455152907-18495-4-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Change the indentation in __acct_update_integrals() to make the function
a little easier to read.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Frederic Weisbecker <fweisbec@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: clark@redhat.com
Cc: eric.dumazet@gmail.com
Cc: fweisbec@gmail.com
Cc: luto@amacapital.net
Link: http://lkml.kernel.org/r/1455152907-18495-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When running a microbenchmark calling an invalid syscall number
in a loop, on a nohz_full CPU, we spend a full 9% of our CPU
time in __acct_update_integrals().
This function converts cputime_t to jiffies, to a timeval, only to
convert the timeval back to microseconds before discarding it.
This patch leaves __acct_update_integrals() functionally equivalent,
but speeds things up by about 12%, with 10 million calls to an
invalid syscall number dropping from 3.7 to 3.25 seconds.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: clark@redhat.com
Cc: eric.dumazet@gmail.com
Cc: fweisbec@gmail.com
Cc: luto@amacapital.net
Link: http://lkml.kernel.org/r/1455152907-18495-2-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
I've been debugging why deadline tasks can cause the RT scheduler to
throttle, even when the deadline tasks are only taking up 50% of the
CPU and RT tasks are not even using 1% of the CPU. Here's what I found.
In order to keep a CPU from being hogged by RT tasks, the deadline
scheduler adds its run time (delta_exec) to the rt_time of the RT
bandwidth. That way, if the two use more than 95% of the CPU within one
second (default settings), the RT tasks are throttled to allow non RT
tasks to run.
Although the deadline tasks add their run time to the RT bandwidth, it
lets the RT tasks do the accounting. This is where the problem lies. If
a deadline task runs for a bit, and no RT tasks are running, then it
will continually add to the RT rt_time that is used to calculate how
much CPU the RT tasks use. But no RT period is in play, and this
accumulation of the runtime never gets reset.
When an RT task finally gets to run, and the watchdog goes off, it can
see that the RT task has used more than it should of, because the
deadline task added all this runtime to its rt_time. Then the RT task
that just woke up gets throttled for no good reason.
I also noticed that when an RT task is queued, it starts the timer to
account for overload and such. But that timer goes off one period
later, which may be too late and the extra rt_time will trigger a
throttle.
This is a quick work around to the problem. When a new RT task is
queued, the bandwidth timer is set to go off immediately. Then the
timer can clear out the extra time added to the rt_time while there was
no RT task running. This stops my tests from triggering the throttle,
and it will still throttle if an RT task runs too much, even while a
deadline task is running.
A better solution may be to subtract the bandwidth that the deadline
task uses from the rt_runtime, and add it back when its finished. Then
there wont be a need for runtime tracking of the time used by deadline
tasks.
I may play with that solution tomorrow.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <juri.lelli@gmail.com>
Cc: <williams@redhat.com>
Cc: Clark Williams
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160216183746.349ec98b@gandalf.local.home
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Playing with SCHED_DEADLINE and cpusets, I found that I was unable to create
new SCHED_DEADLINE tasks, with the error of EBUSY as if the bandwidth was
already used up. I then realized there wa no way to see what bandwidth is
used by the runqueues to debug the issue.
By adding the dl_bw->bw and dl_bw->total_bw to the output of the deadline
info in /proc/sched_debug, this allows us to see what bandwidth has been
reserved and where a problem may exist.
For example, before the issue we see the ratio of the bandwidth:
# cat /proc/sys/kernel/sched_rt_runtime_us
950000
# cat /proc/sys/kernel/sched_rt_period_us
1000000
# grep dl /proc/sched_debug
dl_rq[0]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
dl_rq[1]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
dl_rq[2]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
dl_rq[3]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
dl_rq[4]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
dl_rq[5]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
dl_rq[6]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
dl_rq[7]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 0
Note: (950000 / 1000000) << 20 == 996147
After I played with cpusets and hit the issue, the result is now:
# grep dl /proc/sched_debug
dl_rq[0]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : -104857
dl_rq[1]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 104857
dl_rq[2]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 104857
dl_rq[3]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : 104857
dl_rq[4]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : -104857
dl_rq[5]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : -104857
dl_rq[6]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : -104857
dl_rq[7]:
.dl_nr_running : 0
.dl_bw->bw : 996147
.dl_bw->total_bw : -104857
This shows that there is definitely a problem as we should never have a
negative total bandwidth.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160222212825.756849091@goodmis.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The sched_domain_sysctl setup is only enabled when SCHED_DEBUG is
configured. As debug.c is only compiled when SCHED_DEBUG is configured as
well, move the setup of sched_domain_sysctl into that file.
Note, the (un)register_sched_domain_sysctl() functions had to be changed
from static to allow access to them from core.c.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160222212825.599278093@goodmis.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
As /sys/kernel/debug/sched_features is only created when SCHED_DEBUG is enabled, and the file
debug.c is only compiled when SCHED_DEBUG is enabled, it makes sense to move
sched_feature setup into that file and get rid of the #ifdef.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160222212825.464193063@goodmis.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Andrea Parri reported:
> I found that the following scenario (with CONFIG_RT_GROUP_SCHED=y) is not
> handled correctly:
>
> T1 (prio = 20)
> lock(rtmutex);
>
> T2 (prio = 20)
> blocks on rtmutex (rt_nr_boosted = 0 on T1's rq)
>
> T1 (prio = 20)
> sys_set_scheduler(prio = 0)
> [new_effective_prio == oldprio]
> T1 prio = 20 (rt_nr_boosted = 0 on T1's rq)
>
> The last step is incorrect as T1 is now boosted (c.f., rt_se_boosted());
> in particular, if we continue with
>
> T1 (prio = 20)
> unlock(rtmutex)
> wakeup(T2)
> adjust_prio(T1)
> [prio != rt_mutex_getprio(T1)]
> dequeue(T1)
> rt_nr_boosted = (unsigned long)(-1)
> ...
> T1 prio = 0
>
> then we end up leaving rt_nr_boosted in an "inconsistent" state.
>
> The simple program attached could reproduce the previous scenario; note
> that, as a consequence of the presence of this state, the "assertion"
>
> WARN_ON(!rt_nr_running && rt_nr_boosted)
>
> from dec_rt_group() may trigger.
So normally we dequeue/enqueue tasks in sched_setscheduler(), which
would ensure the accounting stays correct. However in the early PI path
we fail to do so.
So this was introduced at around v3.14, by:
c365c292d0 ("sched: Consider pi boosting in setscheduler()")
which fixed another problem exactly because that dequeue/enqueue, joy.
Fix this by teaching rt about DEQUEUE_SAVE/ENQUEUE_RESTORE and have it
preserve runqueue location with that option. This requires decoupling
the on_rt_rq() state from being on the list.
In order to allow for explicit movement during the SAVE/RESTORE,
introduce {DE,EN}QUEUE_MOVE. We still must use SAVE/RESTORE in these
cases to preserve other invariants.
Respecting the SAVE/RESTORE flags also has the (nice) side-effect that
things like sys_nice()/sys_sched_setaffinity() also do not reorder
FIFO tasks (whereas they used to before this patch).
Reported-by: Andrea Parri <parri.andrea@gmail.com>
Tested-by: Andrea Parri <parri.andrea@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Lets factorize a bit of code there. We'll even have a third user soon.
While at it, standardize the idle update function name against the
others.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Byungchul Park <byungchul.park@lge.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1452700891-21807-3-git-send-email-fweisbec@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
decay_load_missed() cannot handle nagative values, so we need to prevent
using the function with a negative value.
Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E . McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: perterz@infradead.org
Fixes: 5954327548 ("sched/fair: Prepare __update_cpu_load() to handle active tickless")
Link: http://lkml.kernel.org/r/20160115070749.GA1914@X58A-UD3R
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Steven noticed that occasionally a sched_yield() call would not result
in a wait for the next period edge as expected.
It turns out that when we call update_curr_dl() and end up with
delta_exec <= 0, we will bail early and fail to throttle.
Further inspection of the yield code revealed that yield_task_dl()
clearing dl.runtime is wrong too, it will not account the last bit of
runtime which could result in dl.runtime < 0, which in turn means that
replenish would gift us with too much runtime.
Fix both issues by not relying on the dl.runtime value for yield.
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Tested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Clark Williams <williams@redhat.com>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160223122822.GP6357@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
When a cgroup's CPU runqueue is destroyed, it should remove its
remaining load accounting from its parent cgroup.
The current site for doing so it unsuited because its far too late and
unordered against other cgroup removal (->css_free() will be, but we're also
in an RCU callback).
Put it in the ->css_offline() callback, which is the start of cgroup
destruction, right after the group has been made unavailable to
userspace. The ->css_offline() callbacks are called in hierarchical order
after the following v4.4 commit:
aa226ff4a1 ("cgroup: make sure a parent css isn't offlined before its children")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160121212416.GL6357@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
As Jiri pointed out, this recent commit:
f872f5400c ("mm: Add a vm_special_mapping.fault() method")
breaks uprobes: __create_xol_area() doesn't initialize the new ->fault()
method and this obviously leads to kernel crash when the application
tries to execute the probed insn after bp hit.
We probably want to add uprobes_special_mapping_fault(), this allows to
turn xol_area->xol_mapping into a single instance of vm_special_mapping.
But we need a simple fix, so lets change __create_xol() to nullify the
new member as Jiri suggests.
Suggested-by: Jiri Olsa <jolsa@redhat.com>
Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <tipbot@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pratyush Anand <panand@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20160227221128.GA29565@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull perf fixes from Thomas Gleixner:
"A rather largish series of 12 patches addressing a maze of race
conditions in the perf core code from Peter Zijlstra"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Robustify task_function_call()
perf: Fix scaling vs. perf_install_in_context()
perf: Fix scaling vs. perf_event_enable()
perf: Fix scaling vs. perf_event_enable_on_exec()
perf: Fix ctx time tracking by introducing EVENT_TIME
perf: Cure event->pending_disable race
perf: Fix race between event install and jump_labels
perf: Fix cloning
perf: Only update context time when active
perf: Allow perf_release() with !event->ctx
perf: Do not double free
perf: Close install vs. exit race
Pull scheduler fixlet from Thomas Gleixner:
"A trivial printk typo fix"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/deadline: Fix trivial typo in printk() message
The CLOCKSOURCE_MASK(32) macro expands to the same value, but
makes code more readable.
Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Link: http://lkml.kernel.org/r/1456542854-22104-3-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
When perf added a "reg" function to the function tracing event (not a
tracepoint), it caused that event to be displayed as a tracepoint and
could cause errors in tracepoint handling. That was solved by adding a
flag to ignore ftrace non-tracepoint events. But that flag was missed
when displaying events in available_events, which should only contain
tracepoint events.
This broke a documented way to enable all events with:
cat available_events > set_event
As the function non-tracepoint event would cause that to error out.
The commit here fixes that by having the available_events file not list
events that have the ignore flag set.
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Merge tag 'trace-fixes-v4.5-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fix from Steven Rostedt:
"Another small bug reported to me by Chunyu Hu.
When perf added a "reg" function to the function tracing event (not a
tracepoint), it caused that event to be displayed as a tracepoint and
could cause errors in tracepoint handling. That was solved by adding
a flag to ignore ftrace non-tracepoint events. But that flag was
missed when displaying events in available_events, which should only
contain tracepoint events.
This broke a documented way to enable all events with:
cat available_events > set_event
As the function non-tracepoint event would cause that to error out.
The commit here fixes that by having the available_events file not
list events that have the ignore flag set"
* tag 'trace-fixes-v4.5-rc5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing: Fix showing function event in available_events
Pull libnvdimm fixes from Dan Williams:
- Two fixes for compatibility with the ACPI 6.1 specification.
Without these fixes multi-interface DIMMs will fail to be probed, and
address range scrub commands to find memory errors will give results
that the kernel will mis-interpret. For multi-interface DIMMs Linux
will accept either the original 6.0 implementation or 6.1.
For address range scrub we'll only support 6.1 since ACPI formalized
this DSM differently than the original example [1] implemented in
v4.2. The expectation is that production systems will only ever ship
the ACPI 6.1 address range scrub command definition.
- The wider async address range scrub work targeting 4.6 discovered
that the original synchronous implementation in 4.5 is not sizing its
return buffer correctly.
- Arnd caught that my recent fix to the size of the pfn_t flags missed
updating the flags variable used in the pmem driver.
- Toshi found that we mishandle the memremap() return value in
devm_memremap().
* 'libnvdimm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
nvdimm: use 'u64' for pfn flags
devm_memremap: Fix error value when memremap failed
nfit: update address range scrub commands to the acpi 6.1 format
libnvdimm, tools/testing/nvdimm: fix 'ars_status' output buffer sizing
nfit: fix multi-interface dimm handling, acpi6.1 compatibility
As of commit dae6e64d2b ("rcu: Introduce proper blocking to no-CBs kthreads
GP waits") the RCU subsystem started making use of wait queues.
Here we convert all additions of RCU wait queues to use simple wait queues,
since they don't need the extra overhead of the full wait queue features.
Originally this was done for RT kernels[1], since we would get things like...
BUG: sleeping function called from invalid context at kernel/rtmutex.c:659
in_atomic(): 1, irqs_disabled(): 1, pid: 8, name: rcu_preempt
Pid: 8, comm: rcu_preempt Not tainted
Call Trace:
[<ffffffff8106c8d0>] __might_sleep+0xd0/0xf0
[<ffffffff817d77b4>] rt_spin_lock+0x24/0x50
[<ffffffff8106fcf6>] __wake_up+0x36/0x70
[<ffffffff810c4542>] rcu_gp_kthread+0x4d2/0x680
[<ffffffff8105f910>] ? __init_waitqueue_head+0x50/0x50
[<ffffffff810c4070>] ? rcu_gp_fqs+0x80/0x80
[<ffffffff8105eabb>] kthread+0xdb/0xe0
[<ffffffff8106b912>] ? finish_task_switch+0x52/0x100
[<ffffffff817e0754>] kernel_thread_helper+0x4/0x10
[<ffffffff8105e9e0>] ? __init_kthread_worker+0x60/0x60
[<ffffffff817e0750>] ? gs_change+0xb/0xb
...and hence simple wait queues were deployed on RT out of necessity
(as simple wait uses a raw lock), but mainline might as well take
advantage of the more streamline support as well.
[1] This is a carry forward of work from v3.10-rt; the original conversion
was by Thomas on an earlier -rt version, and Sebastian extended it to
additional post-3.10 added RCU waiters; here I've added a commit log and
unified the RCU changes into one, and uprev'd it to match mainline RCU.
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-6-git-send-email-wagi@monom.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
rcu_nocb_gp_cleanup() is called while holding rnp->lock. Currently,
this is okay because the wake_up_all() in rcu_nocb_gp_cleanup() will
not enable the IRQs. lockdep is happy.
By switching over using swait this is not true anymore. swake_up_all()
enables the IRQs while processing the waiters. __do_softirq() can now
run and will eventually call rcu_process_callbacks() which wants to
grap nrp->lock.
Let's move the rcu_nocb_gp_cleanup() call outside the lock before we
switch over to swait.
If we would hold the rnp->lock and use swait, lockdep reports
following:
=================================
[ INFO: inconsistent lock state ]
4.2.0-rc5-00025-g9a73ba0 #136 Not tainted
---------------------------------
inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
rcu_preempt/8 [HC0[0]:SC0[0]:HE1:SE1] takes:
(rcu_node_1){+.?...}, at: [<ffffffff811387c7>] rcu_gp_kthread+0xb97/0xeb0
{IN-SOFTIRQ-W} state was registered at:
[<ffffffff81109b9f>] __lock_acquire+0xd5f/0x21e0
[<ffffffff8110be0f>] lock_acquire+0xdf/0x2b0
[<ffffffff81841cc9>] _raw_spin_lock_irqsave+0x59/0xa0
[<ffffffff81136991>] rcu_process_callbacks+0x141/0x3c0
[<ffffffff810b1a9d>] __do_softirq+0x14d/0x670
[<ffffffff810b2214>] irq_exit+0x104/0x110
[<ffffffff81844e96>] smp_apic_timer_interrupt+0x46/0x60
[<ffffffff81842e70>] apic_timer_interrupt+0x70/0x80
[<ffffffff810dba66>] rq_attach_root+0xa6/0x100
[<ffffffff810dbc2d>] cpu_attach_domain+0x16d/0x650
[<ffffffff810e4b42>] build_sched_domains+0x942/0xb00
[<ffffffff821777c2>] sched_init_smp+0x509/0x5c1
[<ffffffff821551e3>] kernel_init_freeable+0x172/0x28f
[<ffffffff8182cdce>] kernel_init+0xe/0xe0
[<ffffffff8184231f>] ret_from_fork+0x3f/0x70
irq event stamp: 76
hardirqs last enabled at (75): [<ffffffff81841330>] _raw_spin_unlock_irq+0x30/0x60
hardirqs last disabled at (76): [<ffffffff8184116f>] _raw_spin_lock_irq+0x1f/0x90
softirqs last enabled at (0): [<ffffffff810a8df2>] copy_process.part.26+0x602/0x1cf0
softirqs last disabled at (0): [< (null)>] (null)
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(rcu_node_1);
<Interrupt>
lock(rcu_node_1);
*** DEADLOCK ***
1 lock held by rcu_preempt/8:
#0: (rcu_node_1){+.?...}, at: [<ffffffff811387c7>] rcu_gp_kthread+0xb97/0xeb0
stack backtrace:
CPU: 0 PID: 8 Comm: rcu_preempt Not tainted 4.2.0-rc5-00025-g9a73ba0 #136
Hardware name: Dell Inc. PowerEdge R820/066N7P, BIOS 2.0.20 01/16/2014
0000000000000000 000000006d7e67d8 ffff881fb081fbd8 ffffffff818379e0
0000000000000000 ffff881fb0812a00 ffff881fb081fc38 ffffffff8110813b
0000000000000000 0000000000000001 ffff881f00000001 ffffffff8102fa4f
Call Trace:
[<ffffffff818379e0>] dump_stack+0x4f/0x7b
[<ffffffff8110813b>] print_usage_bug+0x1db/0x1e0
[<ffffffff8102fa4f>] ? save_stack_trace+0x2f/0x50
[<ffffffff811087ad>] mark_lock+0x66d/0x6e0
[<ffffffff81107790>] ? check_usage_forwards+0x150/0x150
[<ffffffff81108898>] mark_held_locks+0x78/0xa0
[<ffffffff81841330>] ? _raw_spin_unlock_irq+0x30/0x60
[<ffffffff81108a28>] trace_hardirqs_on_caller+0x168/0x220
[<ffffffff81108aed>] trace_hardirqs_on+0xd/0x10
[<ffffffff81841330>] _raw_spin_unlock_irq+0x30/0x60
[<ffffffff810fd1c7>] swake_up_all+0xb7/0xe0
[<ffffffff811386e1>] rcu_gp_kthread+0xab1/0xeb0
[<ffffffff811089bf>] ? trace_hardirqs_on_caller+0xff/0x220
[<ffffffff81841341>] ? _raw_spin_unlock_irq+0x41/0x60
[<ffffffff81137c30>] ? rcu_barrier+0x20/0x20
[<ffffffff810d2014>] kthread+0x104/0x120
[<ffffffff81841330>] ? _raw_spin_unlock_irq+0x30/0x60
[<ffffffff810d1f10>] ? kthread_create_on_node+0x260/0x260
[<ffffffff8184231f>] ret_from_fork+0x3f/0x70
[<ffffffff810d1f10>] ? kthread_create_on_node+0x260/0x260
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-5-git-send-email-wagi@monom.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
The existing wait queue support has support for custom wake up call
backs, wake flags, wake key (passed to call back) and exclusive
flags that allow wakers to be tagged as exclusive, for limiting
the number of wakers.
In a lot of cases, none of these features are used, and hence we
can benefit from a slimmed down version that lowers memory overhead
and reduces runtime overhead.
The concept originated from -rt, where waitqueues are a constant
source of trouble, as we can't convert the head lock to a raw
spinlock due to fancy and long lasting callbacks.
With the removal of custom callbacks, we can use a raw lock for
queue list manipulations, hence allowing the simple wait support
to be used in -rt.
[Patch is from PeterZ which is based on Thomas version. Commit message is
written by Paul G.
Daniel: - Fixed some compile issues
- Added non-lazy implementation of swake_up_locked as suggested
by Boqun Feng.]
Originally-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: linux-rt-users@vger.kernel.org
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/r/1455871601-27484-2-git-send-email-wagi@monom.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add APIs to send IPIs from driver and arch code.
We have different functions because we allow architecture code to cache the
irq descriptor to avoid lookups. Driver code has to use the irq number and is
subject to more restrictive checks.
[ tglx: Polish the implementation ]
Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: <jason@lakedaemon.net>
Cc: <marc.zyngier@arm.com>
Cc: <jiang.liu@linux.intel.com>
Cc: <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Cc: <lisa.parratt@imgtec.com>
Cc: Qais Yousef <qsyousef@gmail.com>
Link: http://lkml.kernel.org/r/1449580830-23652-12-git-send-email-qais.yousef@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
When dealing with coprocessors we need to find out the actual hwirqs values to
pass on to the firmware so that it knows what it needs to use to receive IPIs
from and send IPIs to Linux cpus.
[ tglx: Fixed the single hwirq IPI case. The hardware irq number does not
change due to the cpu number ]
Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: <jason@lakedaemon.net>
Cc: <marc.zyngier@arm.com>
Cc: <jiang.liu@linux.intel.com>
Cc: <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Cc: <lisa.parratt@imgtec.com>
Cc: Qais Yousef <qsyousef@gmail.com>
Link: http://lkml.kernel.org/r/1449580830-23652-10-git-send-email-qais.yousef@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Add a generic mechanism to dynamically allocate an IPI. Depending on the
underlying implementation this creates either a single Linux irq or a
consective range of Linux irqs. The Linux irq is used later to send IPIs to
other CPUs.
[ tglx: Massaged the code and removed the 'consecutive mask' restriction for
the single IRQ case ]
Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: <jason@lakedaemon.net>
Cc: <marc.zyngier@arm.com>
Cc: <jiang.liu@linux.intel.com>
Cc: <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Cc: <lisa.parratt@imgtec.com>
Cc: Qais Yousef <qsyousef@gmail.com>
Link: http://lkml.kernel.org/r/1449580830-23652-9-git-send-email-qais.yousef@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
We will need to use this function to implement irq_reserve_ipi() later. So
make it non static and move the prototype to irqdomain.h to allow using it
outside irqdomain.c
Signed-off-by: Qais Yousef <qais.yousef@imgtec.com>
Cc: <jason@lakedaemon.net>
Cc: <marc.zyngier@arm.com>
Cc: <jiang.liu@linux.intel.com>
Cc: <ralf@linux-mips.org>
Cc: <linux-mips@linux-mips.org>
Cc: <lisa.parratt@imgtec.com>
Cc: Qais Yousef <qsyousef@gmail.com>
Link: http://lkml.kernel.org/r/1449580830-23652-8-git-send-email-qais.yousef@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Since there is no serialization between task_function_call() doing
task_curr() and the other CPU doing context switches, we could end
up not sending an IPI even if we had to.
And I'm not sure I still buy my own argument we're OK.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174948.340031200@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Completely reworks perf_install_in_context() (again!) in order to
ensure that there will be no ctx time hole between add_event_to_ctx()
and any potential ctx_sched_in().
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174948.279399438@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The recent commit 3e349507d1 ("perf: Fix perf_enable_on_exec() event
scheduling") caused this by moving task_ctx_sched_out() from before
__perf_event_mask_enable() to after it.
The overlooked consequence of that change is that task_ctx_sched_out()
would update the ctx time fields, and now __perf_event_mask_enable()
uses stale time.
In order to fix this, explicitly stop our context's time before
enabling the event(s).
Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Fixes: 3e349507d1 ("perf: Fix perf_enable_on_exec() event scheduling")
Link: http://lkml.kernel.org/r/20160224174948.159242158@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Currently any ctx_sched_in() call will re-start the ctx time tracking,
this means that calls like:
ctx_sched_in(.event_type = EVENT_PINNED);
ctx_sched_in(.event_type = EVENT_FLEXIBLE);
will have a hole in their ctx time tracking. This is likely harmless
but can confuse things a little. By adding EVENT_TIME, we can have the
first ctx_sched_in() (is_active: 0 -> !0) start the time and any
further ctx_sched_in() will leave the timestamps alone.
Secondly, this allows for an early disable like:
ctx_sched_out(.event_type = EVENT_TIME);
which would update the ctx time (if the ctx is active) and any further
calls to ctx_sched_out() would not further modify the ctx time.
For ctx_sched_in() any 0 -> !0 transition will automatically include
EVENT_TIME.
For ctx_sched_out(), any transition that clears EVENT_ALL will
automatically clear EVENT_TIME.
These two rules ensure that under normal circumstances we need not
bother with EVENT_TIME and get natural ctx time behaviour.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174948.100446561@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Because event_sched_out() checks event->pending_disable _before_
actually disabling the event, it can happen that the event fires after
it checks but before it gets disabled.
This would leave event->pending_disable set and the queued irq_work
will try and process it.
However, if the event trigger was during schedule(), the event might
have been de-scheduled by the time the irq_work runs, and
perf_event_disable_local() will fail.
Fix this by checking event->pending_disable _after_ we call
event->pmu->del(). This depends on the latter being a compiler
barrier, such that the compiler does not lift the load and re-creates
the problem.
Tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174948.040469884@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
perf_install_in_context() relies upon the context switch hooks to have
scheduled in events when the IPI misses its target -- after all, if
the task has moved from the CPU (or wasn't running at all), it will
have to context switch to run elsewhere.
This however doesn't appear to be happening.
It is possible for the IPI to not happen (task wasn't running) only to
later observe the task running with an inactive context.
The only possible explanation is that the context switch hooks are not
called. Therefore put in a sync_sched() after toggling the jump_label
to guarantee all CPUs will have them enabled before we install an
event.
A simple if (0->1) sync_sched() will not in fact work, because any
further increment can race and complete before the sync_sched().
Therefore we must jump through some hoops.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174947.980211985@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Alexander reported that when the 'original' context gets destroyed, no
new clones happen.
This can happen irrespective of the ctx switch optimization, any task
can die, even the parent, and we want to continue monitoring the task
hierarchy until we either close the event or no tasks are left in the
hierarchy.
perf_event_init_context() will attempt to pin the 'parent' context
during clone(). At that point current is the parent, and since current
cannot have exited while executing clone(), its context cannot have
passed through perf_event_exit_task_context(). Therefore
perf_pin_task_context() cannot observe ctx->task == TASK_TOMBSTONE.
However, since inherit_event() does:
if (parent_event->parent)
parent_event = parent_event->parent;
it looks at the 'original' event when it does: is_orphaned_event().
This can return true if the context that contains the this event has
passed through perf_event_exit_task_context(). And thus we'll fail to
clone the perf context.
Fix this by adding a new state: STATE_DEAD, which is set by
perf_release() to indicate that the filedesc (or kernel reference) is
dead and there are no observers for our data left.
Only for STATE_DEAD will is_orphaned_event() be true and inhibit
cloning.
STATE_EXIT is otherwise preserved such that is_event_hup() remains
functional and will report when the observed task hierarchy becomes
empty.
Reported-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Fixes: c6e5b73242 ("perf: Synchronously clean up child events")
Link: http://lkml.kernel.org/r/20160224174947.919845295@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In the err_file: fput(event_file) case, the event will not yet have
been attached to a context. However perf_release() does assume it has
been. Cure this.
Tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174947.793996260@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
In case of: err_file: fput(event_file), we'll end up calling
perf_release() which in turn will free the event.
Do not then free the event _again_.
Tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174947.697350349@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Consider the following scenario:
CPU0 CPU1
ctx = find_get_ctx();
perf_event_exit_task_context()
mutex_lock(&ctx->mutex);
perf_install_in_context(ctx, ...);
/* NO-OP */
mutex_unlock(&ctx->mutex);
...
perf_release()
WARN_ON_ONCE(event->state != STATE_EXIT);
Since the event doesn't pass through perf_remove_from_context()
because perf_install_in_context() NO-OPs because the ctx is dead, and
perf_event_exit_task_context() will not observe the event because its
not attached yet, the event->state will not be set.
Solve this by revalidating ctx->task after we acquire ctx->mutex and
failing the event creation as a whole.
Tested-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dvyukov@google.com
Cc: eranian@google.com
Cc: oleg@redhat.com
Cc: panand@redhat.com
Cc: sasha.levin@oracle.com
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/20160224174947.626853419@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The ftrace:function event is only displayed for parsing the function tracer
data. It is not used to enable function tracing, and does not include an
"enable" file in its event directory.
Originally, this event was kept separate from other events because it did
not have a ->reg parameter. But perf added a "reg" parameter for its use
which caused issues, because it made the event available to functions where
it was not compatible for.
Commit 9b63776fa3 "tracing: Do not enable function event with enable"
added a TRACE_EVENT_FL_IGNORE_ENABLE flag that prevented the function event
from being enabled by normal trace events. But this commit missed keeping
the function event from being displayed by the "available_events" directory,
which is used to show what events can be enabled by set_event.
One documented way to enable all events is to:
cat available_events > set_event
But because the function event is displayed in the available_events, this
now causes an INVALID error:
cat: write error: Invalid argument
Reported-by: Chunyu Hu <chuhu@redhat.com>
Fixes: 9b63776fa3 "tracing: Do not enable function event with enable"
Cc: stable@vger.kernel.org # 3.4+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit exports rcu_gp_is_normal() in order to allow it to be used
by rcutorture and rcuperf.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The Kconfig currently controlling compilation of this code is:
init/Kconfig:config TINY_RCU
init/Kconfig: bool
...meaning that it currently is not being built as a module by anyone.
Lets remove the modular code that is essentially orphaned, so that
when reading the code there is no doubt it is builtin-only.
Since module_init translates to device_initcall in the non-modular
case, the init ordering remains unchanged with this commit. We could
consider moving this to an earlier initcall (subsys?) if desired.
We also delete the MODULE_LICENSE tag etc. since all that information
is already contained at the top of the file in the comments.
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
irq_common_data::state_use_accessors is not designed for public use.
Therefore make it private so that people who write code accessing it
directly will get blamed by sparse. Also #undef the macro
__irqd_to_state after used in header files, so that the macro can't be
misused.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
In patch:
"rcu: Add transitivity to remaining rcu_node ->lock acquisitions"
All locking operations on rcu_node::lock are replaced with the wrappers
because of the need of transitivity, which indicates we should never
write code using LOCK primitives alone(i.e. without a proper barrier
following) on rcu_node::lock outside those wrappers. We could detect
this kind of misuses on rcu_node::lock in the future by adding __private
modifier on rcu_node::lock.
To privatize rcu_node::lock, unlock wrappers are also needed. Replacing
spinlock unlocks with these wrappers not only privatizes rcu_node::lock
but also makes it easier to figure out critical sections of rcu_node.
This patch adds __private modifier to rcu_node::lock and makes every
access to it wrapped by ACCESS_PRIVATE(). Besides, unlock wrappers are
added and raw_spin_unlock(&rnp->lock) and its friends are replaced with
those wrappers.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The related warning from gcc 6.0:
In file included from kernel/rcu/tree.c:4630:0:
kernel/rcu/tree_plugin.h:810:40: warning: ‘rcu_data_p’ defined but not used [-Wunused-const-variable]
static struct rcu_data __percpu *const rcu_data_p = &rcu_sched_data;
^~~~~~~~~~
Also remove always redundant rcu_data_p in tree.c.
Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
The "Disabled dynamic grace-period expediting" console message is
currently printed unconditionally. This commit causes it to be
output only when it is impossible to switch between normal and
expedited grace periods, which was the original intent.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Commit #e3663b1024d1 ("rcu: Handle gpnum/completed wrap while dyntick
idle") sets rdp->gpwrap on the wrong side of the "if" statement in
dyntick_save_progress_counter(), that is, it sets it when the CPU is
not idle instead of when it is idle. Of course, if the CPU is not idle,
its rdp->gpnum won't be lagging beind the global rsp->gpnum, which means
that rdp->gpwrap will never be set.
This commit therefore moves this code to the proper leg of that "if"
statement. This change means that the "else" cause is just "return 0"
and the "then" clause ends with "return 1", so also move the "return 0"
to follow the "if", dropping the "else" clause.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Commit 4a81e8328d ("Reduce overhead of cond_resched() checks for RCU")
handles the error case where a nohz_full loops indefinitely in the kernel
with the scheduling-clock interrupt disabled. However, this handling
includes IPIing the CPU running the offending loop, which is not what
we want for real-time workloads. And there are starting to be real-time
CPU-bound in-kernel workloads, and these must be handled without IPIing
the CPU, at least not in the common case. Therefore, this situation can
no longer be dismissed as an error case.
This commit therefore splits the handling out, so that the setting of
bits in the per-CPU rcu_sched_qs_mask variable is done relatively early,
but if the problem persists, resched_cpu() is eventually used to IPI the
CPU containing the offending loop. Assuming that in-kernel CPU-bound
loops used by real-time tasks contain frequent calls cond_resched_rcu_qs()
(as in more than once per few tens of milliseconds), the real-time tasks
will never be IPIed.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
The header comment for rcu_report_qs_rsp() was obsolete, dating well
before the advent of RCU grace-period kthreads. This commit therefore
brings this comment back into alignment with current reality.
Reported-by: Lihao Liang <lihao.liang@cs.ox.ac.uk>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
A zero seems to have escaped earlier true/false substitution efforts,
so this commit changes 0 to false for the ->core_needs_qs boolean field.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
devm_memremap() returns an ERR_PTR() value in case of error.
However, it returns NULL when memremap() failed. This causes
the caller, such as the pmem driver, to proceed and oops later.
Change devm_memremap() to return ERR_PTR(-ENXIO) when memremap()
failed.
Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: <stable@vger.kernel.org>
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
One is by Yang Shi who added a READ_ONCE_NOCHECK() to the scan of the
stack made by the stack tracer. As the stack tracer scans the entire
kernel stack, KASAN triggers seeing it as a "stack out of bounds" error.
As the scan is looking at the contents of the stack from parent functions.
The NOCHECK() tells KASAN that this is done on purpose, and is not some
kind of stack overflow.
The second fix is to the ftrace selftests, to retrieve the PID of executed
commands from the shell with "$!" and not by parsing "jobs".
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Merge tag 'trace-fixes-v4.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes from Steven Rostedt:
"Two more small fixes.
One is by Yang Shi who added a READ_ONCE_NOCHECK() to the scan of the
stack made by the stack tracer. As the stack tracer scans the entire
kernel stack, KASAN triggers seeing it as a "stack out of bounds"
error. As the scan is looking at the contents of the stack from
parent functions. The NOCHECK() tells KASAN that this is done on
purpose, and is not some kind of stack overflow.
The second fix is to the ftrace selftests, to retrieve the PID of
executed commands from the shell with '$!' and not by parsing 'jobs'"
* tag 'trace-fixes-v4.5-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
tracing, kasan: Silence Kasan warning in check_stack of stack_tracer
ftracetest: Fix instance test to use proper shell command for pids
It may be useful to debug writes to the readonly sections of memory,
so provide a cmdline "rodata=off" to allow for this. This can be
expanded in the future to support "log" and "write" modes, but that
will need to be architecture-specific.
This also makes KDB software breakpoints more usable, as read-only
mappings can now be disabled on any kernel.
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Brown <david.brown@linaro.org>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Krause <minipli@googlemail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-hardening@lists.openwall.com
Cc: linux-arch <linux-arch@vger.kernel.org>
Link: http://lkml.kernel.org/r/1455748879-21872-3-git-send-email-keescook@chromium.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Pull perf fixes from Ingo Molnar:
"A handful of CPU hotplug related fixes"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/core: Plug potential memory leak in CPU_UP_PREPARE
perf/core: Remove the bogus and dangerous CPU_DOWN_FAILED hotplug state
perf/core: Remove bogus UP_CANCELED hotplug state
perf/x86/amd/uncore: Plug reference leak
