To de-offload callback processing back onto a CPU, it is necessary
to clear SEGCBLIST_OFFLOAD and notify the nocb GP kthread, which will
then clear its own bit flag and ignore this CPU until further notice.
Whichever of the nocb CB and nocb GP kthreads is last to clear its own
bit notifies the de-offloading worker kthread. Once notified, this
worker kthread can proceed safe in the knowledge that the nocb CB and
GP kthreads will no longer be manipulating this CPU's RCU callback list.
This commit makes this change.
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>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
To de-offload callback processing back onto a CPU, it is necessary to
clear SEGCBLIST_OFFLOAD and notify the nocb CB kthread, which will then
clear its own bit flag and go to sleep to stop handling callbacks. This
commit makes that change. It will also be necessary to notify the nocb
GP kthread in this same way, which is the subject of a follow-on commit.
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>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
[ paulmck: Add export per kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
How the rdp->cblist enabled state is treated at CPU-hotplug time depends
on whether or not that ->cblist is offloaded.
1) Not offloaded: The ->cblist is disabled when the CPU goes down. All
its callbacks are migrated and none can to enqueued until after some
later CPU-hotplug operation brings the CPU back up.
2) Offloaded: The ->cblist is not disabled on CPU down because the CB/GP
kthreads must finish invoking the remaining callbacks. There is thus
no need to re-enable it on CPU up.
Since the ->cblist offloaded state is set in stone at boot, it cannot
change between CPU down and CPU up. So 1) and 2) are symmetrical.
However, given runtime toggling of the offloaded state, there are two
additional asymmetrical scenarios:
3) The ->cblist is not offloaded when the CPU goes down. The ->cblist
is later toggled to offloaded and then the CPU comes back up.
4) The ->cblist is offloaded when the CPU goes down. The ->cblist is
later toggled to no longer be offloaded and then the CPU comes back up.
Scenario 4) is currently handled correctly. The ->cblist remains enabled
on CPU down and gets re-initialized on CPU up. The toggling operation
will wait until ->cblist is empty, so ->cblist will remain empty until
CPU-up time.
The scenario 3) would run into trouble though, as the rdp is disabled
on CPU down and not re-initialized/re-enabled on CPU up. Except that
in this case, ->cblist is guaranteed to be empty because all its
callbacks were migrated away at CPU-down time. And the CPU-up code
already initializes and enables any empty ->cblist structures in order
to handle the possibility of early-boot invocations of call_rcu() in
the case where such invocations don't occur. So all that need be done
is to adjust the locking.
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>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Offloading and de-offloading RCU callback processes must be done
carefully. There must never be a time at which callback processing is
disabled because the task driving the offloading or de-offloading might be
preempted or otherwise stalled at that point in time, which would result
in OOM due to calbacks piling up indefinitely. This implies that there
will be times during which a given CPU's callbacks might be concurrently
invoked by both that CPU's RCU_SOFTIRQ handler (or, equivalently, that
CPU's rcuc kthread) and by that CPU's rcuo kthread.
This situation could fatally confuse both rcu_barrier() and the
CPU-hotplug offlining process, so these must be excluded during any
concurrent-callback-invocation period. In addition, during times of
concurrent callback invocation, changes to ->cblist must be protected
both as needed for RCU_SOFTIRQ and as needed for the rcuo kthread.
This commit therefore defines and documents the states for a state
machine that coordinates offloading and deoffloading.
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>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Neeraj Upadhyay <neeraju@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Inspired-by: Paul E. McKenney <paulmck@kernel.org>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds debug checks near the end of rcu_do_batch() that emit
warnings if an empty rcu_segcblist structure has non-zero segment counts,
or, conversely, if a non-empty structure has all-zero segment counts.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Fix queue/segment-length checks. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds tracing to track how the segcb list changes before/after
acceleration, during queuing and during dequeuing.
This tracing helped discover an optimization that avoided needless GP
requests when no callbacks were accelerated. The tracing overhead is
minimal as each segment's length is now stored in the respective segment.
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The full memory barriers in rcu_segcblist_enqueue() and in rcu_do_batch()
are not needed because rcu_segcblist_add_len(), and thus also
rcu_segcblist_inc_len(), already includes a memory barrier *before*
and *after* the length of the list is updated.
This commit therefore removes these redundant smp_mb() invocations.
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Add counting of segment lengths of segmented callback list.
This will be useful for a number of things such as knowing how big the
ready-to-execute segment have gotten. The immediate benefit is ability
to trace how the callbacks in the segmented callback list change.
Also this patch remove hacks related to using donecbs's ->len field as a
temporary variable to save the segmented callback list's length. This cannot be
done anymore and is not needed.
Also fix SRCU:
The negative counting of the unsegmented list cannot be used to adjust
the segmented one. To fix this, sample the unsegmented length in
advance, and use it after CB execution to adjust the segmented list's
length.
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
One counter-intuitive property of RCU is the fact that full memory
barriers are needed both before and after updates to the full
(non-segmented) length. This patch therefore helps to assist the
reader's intuition by adding appropriate comments.
[ paulmck: Wordsmithing. ]
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Preparations to doing i386 compat elf_prstatus sanely - rather than duplicating
the beginning of compat_elf_prstatus, take these fields into a separate
structure (compat_elf_prstatus_common), so that it could be reused. Due to
the incestous relationship between binfmt_elf.c and compat_binfmt_elf.c we
need the same shape change done to native struct elf_prstatus, gathering the
fields prior to pr_reg into a new structure (struct elf_prstatus_common).
Fortunately, offset of pr_reg is always a multiple of 16 with no padding
right before it, so it's possible to turn all the stuff prior to it into
a single member without disturbing the layout.
[build fix from Geert Uytterhoeven folded in]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull networking fixes from Jakub Kicinski:
"Networking fixes, including fixes from netfilter, wireless and bpf
trees.
Current release - regressions:
- mt76: fix NULL pointer dereference in mt76u_status_worker and
mt76s_process_tx_queue
- net: ipa: fix interconnect enable bug
Current release - always broken:
- netfilter: fixes possible oops in mtype_resize in ipset
- ath11k: fix number of coding issues found by static analysis tools
and spurious error messages
Previous releases - regressions:
- e1000e: re-enable s0ix power saving flows for systems with the
Intel i219-LM Ethernet controllers to fix power use regression
- virtio_net: fix recursive call to cpus_read_lock() to avoid a
deadlock
- ipv4: ignore ECN bits for fib lookups in fib_compute_spec_dst()
- sysfs: take the rtnl lock around XPS configuration
- xsk: fix memory leak for failed bind and rollback reservation at
NETDEV_TX_BUSY
- r8169: work around power-saving bug on some chip versions
Previous releases - always broken:
- dcb: validate netlink message in DCB handler
- tun: fix return value when the number of iovs exceeds MAX_SKB_FRAGS
to prevent unnecessary retries
- vhost_net: fix ubuf refcount when sendmsg fails
- bpf: save correct stopping point in file seq iteration
- ncsi: use real net-device for response handler
- neighbor: fix div by zero caused by a data race (TOCTOU)
- bareudp: fix use of incorrect min_headroom size and a false
positive lockdep splat from the TX lock
- mvpp2:
- clear force link UP during port init procedure in case
bootloader had set it
- add TCAM entry to drop flow control pause frames
- fix PPPoE with ipv6 packet parsing
- fix GoP Networking Complex Control config of port 3
- fix pkt coalescing IRQ-threshold configuration
- xsk: fix race in SKB mode transmit with shared cq
- ionic: account for vlan tag len in rx buffer len
- stmmac: ignore the second clock input, current clock framework does
not handle exclusive clock use well, other drivers may reconfigure
the second clock
Misc:
- ppp: change PPPIOCUNBRIDGECHAN ioctl request number to follow
existing scheme"
* tag 'net-5.11-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (99 commits)
net: dsa: lantiq_gswip: Fix GSWIP_MII_CFG(p) register access
net: dsa: lantiq_gswip: Enable GSWIP_MII_CFG_EN also for internal PHYs
net: lapb: Decrease the refcount of "struct lapb_cb" in lapb_device_event
r8169: work around power-saving bug on some chip versions
net: usb: qmi_wwan: add Quectel EM160R-GL
selftests: mlxsw: Set headroom size of correct port
net: macb: Correct usage of MACB_CAPS_CLK_HW_CHG flag
ibmvnic: fix: NULL pointer dereference.
docs: networking: packet_mmap: fix old config reference
docs: networking: packet_mmap: fix formatting for C macros
vhost_net: fix ubuf refcount incorrectly when sendmsg fails
bareudp: Fix use of incorrect min_headroom size
bareudp: set NETIF_F_LLTX flag
net: hdlc_ppp: Fix issues when mod_timer is called while timer is running
atlantic: remove architecture depends
erspan: fix version 1 check in gre_parse_header()
net: hns: fix return value check in __lb_other_process()
net: sched: prevent invalid Scell_log shift count
net: neighbor: fix a crash caused by mod zero
ipv4: Ignore ECN bits for fib lookups in fib_compute_spec_dst()
...
Tasks Trace RCU uses irq_work_queue() to safely awaken its grace-period
kthread, so this commit therefore causes the TASKS_TRACE_RCU Kconfig
option select the IRQ_WORK Kconfig option.
Reported-by: kernel test robot <lkp@intel.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds self tests for early-boot use of RCU-tasks grace periods.
It tests all three variants (Rude, Tasks, and Tasks Trace) and covers
both synchronous (e.g., synchronize_rcu_tasks()) and asynchronous (e.g.,
call_rcu_tasks()) grace-period APIs.
Self-tests are run only in kernels built with CONFIG_PROVE_RCU=y.
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
[ paulmck: Handle CONFIG_PROVE_RCU=n and identify test cases' callbacks. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a lockdep_assert_irqs_disabled() call to the
helper macros that release the rcu_node structure's ->lock, namely
to raw_spin_unlock_rcu_node(), raw_spin_unlock_irq_rcu_node() and
raw_spin_unlock_irqrestore_rcu_node(). The point of this is to help track
down a situation where lockdep appears to be insisting that interrupts
are enabled while holding an rcu_node structure's ->lock.
Link: https://lore.kernel.org/lkml/20201111133813.GA81547@elver.google.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a number of lockdep_assert_irqs_disabled() calls
to rcu_sched_clock_irq() and a number of the functions that it calls.
The point of this is to help track down a situation where lockdep appears
to be insisting that interrupts are enabled within these functions, which
should only ever be invoked from the scheduling-clock interrupt handler.
Link: https://lore.kernel.org/lkml/20201111133813.GA81547@elver.google.com/
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Rewrite kcsan_prandom_u32_max() to not depend on code that might be
instrumented, removing any dependency on lib/random32.c. The rewrite
implements a simple linear congruential generator, that is sufficient
for our purposes (for udelay() and skip_watch counter randomness).
The initial motivation for this was to allow enabling KCSAN for
kernel/sched (remove KCSAN_SANITIZE := n from kernel/sched/Makefile),
with CONFIG_DEBUG_PREEMPT=y. Without this change, we could observe
recursion:
check_access() [via instrumentation]
kcsan_setup_watchpoint()
reset_kcsan_skip()
kcsan_prandom_u32_max()
get_cpu_var()
preempt_disable()
preempt_count_add() [in kernel/sched/core.c]
check_access() [via instrumentation]
Note, while this currently does not affect an unmodified kernel, it'd be
good to keep a KCSAN kernel working when KCSAN_SANITIZE := n is removed
from kernel/sched/Makefile to permit testing scheduler code with KCSAN
if desired.
Fixes: cd290ec246 ("kcsan: Use tracing-safe version of prandom")
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, RCU CPU stall warning messages will NMI whatever CPU looks
like it is blocking either the current grace period or the grace-period
kthread. This can produce confusing output if the target CPU is offline.
This commit therefore checks for offline CPUs.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
When the RCU CPU stall-warning code detects that the RCU grace-period
kthread is being starved, it dumps that kthread's stack. This can
sometimes be useful, but it is also useful to know what is running on the
CPU that this kthread is attempting to run on. This commit therefore
adds a stack trace of this CPU in order to help track down whatever it
is that might be preventing RCU's grace-period kthread from running.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
There is a rather obtuse string that can be printed as part of an
expedited RCU CPU stall-warning message that starts with "blocking
rcu_node structures". Under normal conditions, most of this message
is just repeating the list of CPUs blocking the current expedited grace
period, but in a manner that is rather difficult to read. This commit
therefore marks this message as "(internal RCU debug)" in an effort to
give people the option of avoiding wasting time attempting to extract
nonexistent additional meaning from this portion of the message.
Reported-by: Jonathan Lemon <bsd@fb.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds the desired CPU, the actual CPU, and nr_cpu_ids to
the wrong-CPU warning in scftorture_invoker(), the better to help with
debugging.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
RCU guarantees that anything seen by a given reader will also be seen
after any grace period that must wait on that reader. This is very likely
to hold based on inspection, but the advantage of having rcutorture do
the inspecting is that rcutorture doesn't mind inspecting frequently
and often.
This commit therefore adds code to test RCU's global memory ordering.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds writer-side testing of the polling grace-period API.
One test verifies that the polling API sees a grace period caused by
some other mechanism. Another test verifies that using the polling API
to wait for a grace period does not result in too-short grace periods.
A third test verifies that the polling API does not report
completion within a read-side critical section. A fourth and final
test verifies that the polling API does report completion given an
intervening grace period.
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The new get_state_synchronize_srcu(), start_poll_synchronize_srcu() and
poll_state_synchronize_srcu() functions need to be tested, and so this
commit prepares by renaming the rcu_torture_ops field ->get_state to
->get_gp_state in order to be consistent with the upcoming ->start_gp_poll
and ->poll_gp_state fields.
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
There is a need for a polling interface for SRCU grace
periods, so this commit supplies get_state_synchronize_srcu(),
start_poll_synchronize_srcu(), and poll_state_synchronize_srcu() for this
purpose. The first can be used if future grace periods are inevitable
(perhaps due to a later call_srcu() invocation), the second if future
grace periods might not otherwise happen, and the third to check if a
grace period has elapsed since the corresponding call to either of the
first two.
As with get_state_synchronize_rcu() and cond_synchronize_rcu(),
the return value from either get_state_synchronize_srcu() or
start_poll_synchronize_srcu() must be passed in to a later call to
poll_state_synchronize_srcu().
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
[ paulmck: Add EXPORT_SYMBOL_GPL() per kernel test robot feedback. ]
[ paulmck: Apply feedback from Neeraj Upadhyay. ]
Link: https://lore.kernel.org/lkml/20201117004017.GA7444@paulmck-ThinkPad-P72/
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
There is a need for a polling interface for SRCU grace
periods, so this commit supplies get_state_synchronize_srcu(),
start_poll_synchronize_srcu(), and poll_state_synchronize_srcu() for this
purpose. The first can be used if future grace periods are inevitable
(perhaps due to a later call_srcu() invocation), the second if future
grace periods might not otherwise happen, and the third to check if a
grace period has elapsed since the corresponding call to either of the
first two.
As with get_state_synchronize_rcu() and cond_synchronize_rcu(),
the return value from either get_state_synchronize_srcu() or
start_poll_synchronize_srcu() must be passed in to a later call to
poll_state_synchronize_srcu().
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
[ paulmck: Add EXPORT_SYMBOL_GPL() per kernel test robot feedback. ]
[ paulmck: Apply feedback from Neeraj Upadhyay. ]
Link: https://lore.kernel.org/lkml/20201117004017.GA7444@paulmck-ThinkPad-P72/
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
There is a need for a polling interface for SRCU grace periods.
This polling needs to initiate an SRCU grace period without having
to queue (and manage) a callback. This commit therefore splits the
Tree SRCU __call_srcu() function into callback-initialization and
queuing/start-grace-period portions, with the latter in a new function
named srcu_gp_start_if_needed(). This function may be passed a NULL
callback pointer, in which case it will refrain from queuing anything.
Why have the new function mess with queuing? Locking considerations,
of course!
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
There is a need for a polling interface for SRCU grace periods.
This polling needs to initiate an SRCU grace period without
having to queue (and manage) a callback. This commit therefore
splits the Tiny SRCU call_srcu() function into callback-queuing and
start-grace-period portions, with the latter in a new function named
srcu_gp_start_if_needed().
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
There is a need for a polling interface for SRCU grace periods. This
polling needs to distinguish between an SRCU instance being idle on the
one hand or in the middle of a grace period on the other. This commit
therefore converts the Tiny SRCU srcu_struct structure's srcu_idx from
a defacto boolean to a free-running counter, using the bottom bit to
indicate that a grace period is in progress. The second-from-bottom
bit is thus used as the index returned by srcu_read_lock().
Link: https://lore.kernel.org/rcu/20201112201547.GF3365678@moria.home.lan/
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
[ paulmck: Fix ->srcu_lock_nesting[] indexing per Neeraj Upadhyay. ]
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Expedited RCU grace periods send IPIs to all non-idle CPUs, and thus can
disrupt time-critical code in real-time applications. However, there
is a portion of boot-time processing (presumably before any real-time
applications have started) where expedited RCU grace periods are the only
option. And so it is that experience with the -rt patchset indicates that
PREEMPT_RT systems should always set the rcupdate.rcu_normal_after_boot
kernel boot parameter.
This commit therefore makes the post-boot application environment safe
for real-time applications by making PREEMPT_RT systems disable the
rcupdate.rcu_normal_after_boot kernel boot parameter and acting as
if this parameter had been set. This means that post-boot calls to
synchronize_rcu_expedited() will be treated as if they were instead
calls to synchronize_rcu(), thus preventing the IPIs, and thus avoiding
disrupting real-time applications.
Suggested-by: Luiz Capitulino <lcapitulino@redhat.com>
Acked-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Julia Cartwright <julia@ni.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ paulmck: Update kernel-parameters.txt accordingly. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
PREEMPT_RT systems have long used the rcutree.use_softirq kernel
boot parameter to avoid use of RCU_SOFTIRQ handlers, which can disrupt
real-time applications by invoking callbacks during return from interrupts
that arrived while executing time-critical code. This kernel boot
parameter instead runs RCU core processing in an 'rcuc' kthread, thus
allowing the scheduler to do its job of avoiding disrupting time-critical
code.
This commit therefore disables the rcutree.use_softirq kernel boot
parameter on PREEMPT_RT systems, thus forcing such systems to do RCU
core processing in 'rcuc' kthreads. This approach has long been in
use by users of the -rt patchset, and there have been no complaints.
There is therefore no way for the system administrator to override this
choice, at least without modifying and rebuilding the kernel.
Signed-off-by: Scott Wood <swood@redhat.com>
[bigeasy: Reword commit message]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ paulmck: Update kernel-parameters.txt accordingly. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
On PREEMPT_RT kernels, RCU callbacks are deferred to the `rcuc' kthread.
This can stall RCU grace periods due to lengthy preemption not only of RCU
readers but also of 'rcuc' kthreads, either of which prevent grace periods
from completing, which can in turn result in OOM. Because PREEMPT_RT
kernels have more kthreads that can block grace periods, it is more
important for such kernels to enable RCU_BOOST.
This commit therefore makes RCU_BOOST the default on PREEMPT_RT.
RCU_BOOST can still be manually disabled if need be.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a call to kasan_record_aux_stack() in kvfree_call_rcu()
in order to record the call stack of the code that caused the object
to be freed. Please note that this function does not update the
allocated/freed state, which is important because RCU readers might
still be referencing this object.
Acked-by: Dmitry Vyukov <dvyukov@google.com>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_do_batch() function extracts the ready-to-invoke callbacks
from the rcu_segcblist located in the ->cblist field of the current
CPU's rcu_data structure. These callbacks are first moved to a local
(unsegmented) rcu_cblist. The rcu_do_batch() function then uses this
rcu_cblist's ->len field to count how many CBs it has invoked, but it
does so by counting that field down from zero. Finally, this function
negates the value in this ->len field (resulting in a positive number)
and subtracts the result from the ->len field of the current CPU's
->cblist field.
Except that it is sometimes necessary for rcu_do_batch() to stop invoking
callbacks mid-stream, despite there being more ready to invoke, for
example, if a high-priority task wakes up. In this case the remaining
not-yet-invoked callbacks are requeued back onto the CPU's ->cblist,
but remain in the ready-to-invoke segment of that list. As above, the
negative of the local rcu_cblist's ->len field is still subtracted from
the ->len field of the current CPU's ->cblist field.
The design of counting down from 0 is confusing and error-prone, plus
use of a positive count will make it easier to provide a uniform and
consistent API to deal with the per-segment counts that are added
later in this series. For example, rcu_segcblist_extract_done_cbs()
can unconditionally populate the resulting unsegmented list's ->len
field during extraction.
This commit therefore explicitly counts how many callbacks were executed
in rcu_do_batch() itself, counting up from zero, and then uses that
to update the per-CPU segcb list's ->len field, without relying on the
downcounting of rcl->len from zero.
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Pull RCU fix from Paul McKenney:
"This is a fix for a regression in the v5.10 merge window, but it was
reported quite late in the v5.10 process, plus generating and testing
the fix took some time.
The regression is due to commit 36dadef23f ("kprobes: Init kprobes
in early_initcall") which on powerpc can use RCU Tasks before
initialization, resulting in boot failures.
The fix is straightforward, simply moving initialization of RCU Tasks
before the early_initcall()s. The fix has been exposed to -next and
kbuild test robot testing, and has been tested by the PowerPC guys"
* 'rcu/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
rcu-tasks: Move RCU-tasks initialization to before early_initcall()
Latest bpf tree has a bug for bpf_iter selftest:
$ ./test_progs -n 4/25
test_bpf_sk_storage_get:PASS:bpf_iter_bpf_sk_storage_helpers__open_and_load 0 nsec
test_bpf_sk_storage_get:PASS:socket 0 nsec
...
do_dummy_read:PASS:read 0 nsec
test_bpf_sk_storage_get:FAIL:bpf_map_lookup_elem map value wasn't set correctly
(expected 1792, got -1, err=0)
#4/25 bpf_sk_storage_get:FAIL
#4 bpf_iter:FAIL
Summary: 0/0 PASSED, 0 SKIPPED, 2 FAILED
When doing merge conflict resolution, Commit 4bfc471484 missed to
save curr_task to seq_file private data. The task pointer in seq_file
private data is passed to bpf program. This caused NULL-pointer task
passed to bpf program which will immediately return upon checking
whether task pointer is NULL.
This patch added back the assignment of curr_task to seq_file private
data and fixed the issue.
Fixes: 4bfc471484 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20201231052418.577024-1-yhs@fb.com
Pull io_uring fixes from Jens Axboe:
"A few fixes that should go into 5.11, all marked for stable as well:
- Fix issue around identity COW'ing and users that share a ring
across processes
- Fix a hang associated with unregistering fixed files (Pavel)
- Move the 'process is exiting' cancelation a bit earlier, so
task_works aren't affected by it (Pavel)"
* tag 'io_uring-5.11-2021-01-01' of git://git.kernel.dk/linux-block:
kernel/io_uring: cancel io_uring before task works
io_uring: fix io_sqe_files_unregister() hangs
io_uring: add a helper for setting a ref node
io_uring: don't assume mm is constant across submits
For cancelling io_uring requests it needs either to be able to run
currently enqueued task_works or having it shut down by that moment.
Otherwise io_uring_cancel_files() may be waiting for requests that won't
ever complete.
Go with the first way and do cancellations before setting PF_EXITING and
so before putting the task_work infrastructure into a transition state
where task_work_run() would better not be called.
Cc: stable@vger.kernel.org # 5.5+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Daniel Borkmann says:
====================
pull-request: bpf 2020-12-28
The following pull-request contains BPF updates for your *net* tree.
There is a small merge conflict between bpf tree commit 69ca310f34
("bpf: Save correct stopping point in file seq iteration") and net tree
commit 66ed594409 ("bpf/task_iter: In task_file_seq_get_next use
task_lookup_next_fd_rcu"). The get_files_struct() does not exist anymore
in net, so take the hunk in HEAD and add the `info->tid = curr_tid` to
the error path:
[...]
curr_task = task_seq_get_next(ns, &curr_tid, true);
if (!curr_task) {
info->task = NULL;
info->tid = curr_tid;
return NULL;
}
/* set info->task and info->tid */
[...]
We've added 10 non-merge commits during the last 9 day(s) which contain
a total of 11 files changed, 75 insertions(+), 20 deletions(-).
The main changes are:
1) Various AF_XDP fixes such as fill/completion ring leak on failed bind and
fixing a race in skb mode's backpressure mechanism, from Magnus Karlsson.
2) Fix latency spikes on lockdep enabled kernels by adding a rescheduling
point to BPF hashtab initialization, from Eric Dumazet.
3) Fix a splat in task iterator by saving the correct stopping point in the
seq file iteration, from Jonathan Lemon.
4) Fix BPF maps selftest by adding retries in case hashtab returns EBUSY
errors on update/deletes, from Andrii Nakryiko.
5) Fix BPF selftest error reporting to something more user friendly if the
vmlinux BTF cannot be found, from Kamal Mostafa.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull workqueue update from Tejun Heo:
"The same as the cgroup tree - one commit which was scheduled for the
5.11 merge window.
All the commit does is avoding spurious worker wakeups from workqueue
allocation / config change path to help cpuisol use cases"
* 'for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: Kick a worker based on the actual activation of delayed works
Pull cgroup updates from Tejun Heo:
"These three patches were scheduled for the merge window but I forgot
to send them out. Sorry about that.
None of them are significant and they fit well in a fix pull request
too - two are cosmetic and one fixes a memory leak in the mount option
parsing path"
* 'for-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: Fix memory leak when parsing multiple source parameters
cgroup/cgroup.c: replace 'of->kn->priv' with of_cft()
kernel: cgroup: Mundane spelling fixes throughout the file
Pull timer fixes from Ingo Molnar:
"Update/fix two CPU sanity checks in the hotplug and the boot code, and
fix a typo in the Kconfig help text.
[ Context: the first two commits are the result of an ongoing
annotation+review work of (intentional) tick_do_timer_cpu() data
races reported by KCSAN, but the annotations aren't fully cooked
yet ]"
* tag 'timers-urgent-2020-12-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timekeeping: Fix spelling mistake in Kconfig "fullfill" -> "fulfill"
tick/sched: Remove bogus boot "safety" check
tick: Remove pointless cpu valid check in hotplug code
