Memory barrier instrumentation is crucial to avoid false positives. To
avoid surprises, run a simple test case in the boot-time selftest to
ensure memory barriers are still instrumented correctly.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Adds test cases to check that memory barriers are instrumented
correctly, and detection of missing memory barriers is working as
intended if CONFIG_KCSAN_STRICT=y.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Due to reordering accesses with weak memory modeling, any access can now
appear as "(reordered)".
Match any permutation of accesses if CONFIG_KCSAN_WEAK_MEMORY=y, so that
we effectively match an access if it is denoted "(reordered)" or not.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Also show the location the access was reordered to. An example report:
| ==================================================================
| BUG: KCSAN: data-race in test_kernel_wrong_memorder / test_kernel_wrong_memorder
|
| read-write to 0xffffffffc01e61a8 of 8 bytes by task 2311 on cpu 5:
| test_kernel_wrong_memorder+0x57/0x90
| access_thread+0x99/0xe0
| kthread+0x2ba/0x2f0
| ret_from_fork+0x22/0x30
|
| read-write (reordered) to 0xffffffffc01e61a8 of 8 bytes by task 2310 on cpu 7:
| test_kernel_wrong_memorder+0x57/0x90
| access_thread+0x99/0xe0
| kthread+0x2ba/0x2f0
| ret_from_fork+0x22/0x30
| |
| +-> reordered to: test_kernel_wrong_memorder+0x80/0x90
|
| Reported by Kernel Concurrency Sanitizer on:
| CPU: 7 PID: 2310 Comm: access_thread Not tainted 5.14.0-rc1+ #18
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-2 04/01/2014
| ==================================================================
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The scoping of an access simply denotes the scope in which it may be
reordered. However, in reports, it'll be less confusing to say the
access is "reordered". This is more accurate when the race occurred.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Add the core memory barrier instrumentation functions. These invalidate
the current in-flight reordered access based on the rules for the
respective barrier types and in-flight access type.
To obtain barrier instrumentation that can be disabled via __no_kcsan
with appropriate compiler-support (and not just with objtool help),
barrier instrumentation repurposes __atomic_signal_fence(), instead of
inserting explicit calls. Crucially, __atomic_signal_fence() normally
does not map to any real instructions, but is still intercepted by
fsanitize=thread. As a result, like any other instrumentation done by
the compiler, barrier instrumentation can be disabled with __no_kcsan.
Unfortunately Clang and GCC currently differ in their __no_kcsan aka
__no_sanitize_thread behaviour with respect to builtin atomics (and
__tsan_func_{entry,exit}) instrumentation. This is already reflected in
Kconfig.kcsan's dependencies for KCSAN_WEAK_MEMORY. A later change will
introduce support for newer versions of Clang that can implement
__no_kcsan to also remove the additional instrumentation introduced by
KCSAN_WEAK_MEMORY.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Add support for modeling a subset of weak memory, which will enable
detection of a subset of data races due to missing memory barriers.
KCSAN's approach to detecting missing memory barriers is based on
modeling access reordering, and enabled if `CONFIG_KCSAN_WEAK_MEMORY=y`,
which depends on `CONFIG_KCSAN_STRICT=y`. The feature can be enabled or
disabled at boot and runtime via the `kcsan.weak_memory` boot parameter.
Each memory access for which a watchpoint is set up, is also selected
for simulated reordering within the scope of its function (at most 1
in-flight access).
We are limited to modeling the effects of "buffering" (delaying the
access), since the runtime cannot "prefetch" accesses (therefore no
acquire modeling). Once an access has been selected for reordering, it
is checked along every other access until the end of the function scope.
If an appropriate memory barrier is encountered, the access will no
longer be considered for reordering.
When the result of a memory operation should be ordered by a barrier,
KCSAN can then detect data races where the conflict only occurs as a
result of a missing barrier due to reordering accesses.
Suggested-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Avoid checking scoped accesses from nested contexts (such as nested
interrupts or in scheduler code) which share the same kcsan_ctx.
This is to avoid detecting false positive races of accesses in the same
thread with currently scoped accesses: consider setting up a watchpoint
for a non-scoped (normal) access that also "conflicts" with a current
scoped access. In a nested interrupt (or in the scheduler), which shares
the same kcsan_ctx, we cannot check scoped accesses set up in the parent
context -- simply ignore them in this case.
With the introduction of kcsan_ctx::disable_scoped, we can also clean up
kcsan_check_scoped_accesses()'s recursion guard, and do not need to
modify the list's prev pointer.
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
They are implicitly zero-initialized, remove explicit initialization.
It keeps the upcoming additions to kcsan_ctx consistent with the rest.
No functional change intended.
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Factor out the switch statement reading instrumented memory into a
helper read_instrumented_memory().
No functional change.
Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
nr_running is never modified remotely after the schedule callback in
wakeup path is removed.
Rather nr_running is often accessed with other fields in the pool
together, so the cacheline_aligned for nr_running isn't needed.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In unbind_workers(), there are two pool->lock held sections separated
by the code of zapping nr_running. wake_up_worker() needs to be in
pool->lock held section and after zapping nr_running. And zapping
nr_running had to be after schedule() when the local wake up
functionality was in use. Now, the call to schedule() has been removed
along with the local wake up functionality, so the code can be merged
into the same pool->lock held section.
The diffstat shows that it is other code moved down because the diff
tools can not know the meaning of merging lock sections by swapping
two code blocks.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The commit 6d25be5782 ("sched/core, workqueues: Distangle worker
accounting from rq lock") changed the schedule callbacks for workqueue
and moved the schedule callback from the wakeup code to at end of
schedule() in the worker's process context.
It means that the callback wq_worker_running() is guaranteed that
it sees the %WORKER_UNBOUND flag after scheduled since unbind_workers()
is running on the same CPU that all the pool's workers bound to.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Long time before, workers are not ALL bound after CPU_ONLINE, they can
still be running in other CPUs before self rebinding.
But the commit a9ab775bca ("workqueue: directly restore CPU affinity
of workers from CPU_ONLINE") makes rebind_workers() bind them all.
So all workers are on the CPU before the CPU is down.
And the comment in unbind_workers() refers to the workers "which are
still executing works from before the last CPU down" is outdated.
Just removed it.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The commit 6d25be5782 ("sched/core, workqueues: Distangle worker
accounting from rq lock") changed the schedule callbacks for workqueue
and removed the local-wake-up functionality.
Now the wakingup of workers is done by normal fashion and workers not
yet migrated to the specific CPU in concurrency managed pool can also
be woken up by workers that already bound to the specific cpu now.
So this advanced kicking of the idle workers to migrate them to the
associated CPU is unneeded now.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The semantics of the rlimit max values differs from ucounts itself. When
creating a new userns, we store the current rlimit of the process in
ucount_max. Thus, the value of the limit in the parent userns is saved
in the created one.
The problem is that now we are taking the maximum value for counter from
the same userns. So for init_user_ns it will always be RLIM_INFINITY.
To fix the problem we need to check the counter value with the max value
stored in userns.
Reproducer:
su - test -c "ulimit -u 3; sleep 5 & sleep 6 & unshare -U --map-root-user sh -c 'sleep 7 & sleep 8 & date; wait'"
Before:
[1] 175
[2] 176
Fri Nov 26 13:48:20 UTC 2021
[1]- Done sleep 5
[2]+ Done sleep 6
After:
[1] 167
[2] 168
sh: fork: retry: Resource temporarily unavailable
sh: fork: retry: Resource temporarily unavailable
sh: fork: retry: Resource temporarily unavailable
sh: fork: retry: Resource temporarily unavailable
sh: fork: retry: Resource temporarily unavailable
sh: fork: retry: Resource temporarily unavailable
sh: fork: retry: Resource temporarily unavailable
sh: fork: Interrupted system call
[1]- Done sleep 5
[2]+ Done sleep 6
Fixes: c54b245d01 ("Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace")
Reported-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Alexey Gladkov <legion@kernel.org>
Link: https://lkml.kernel.org/r/024ec805f6e16896f0b23e094773790d171d2c1c.1638218242.git.legion@kernel.org
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Allow the rcu_nocbs kernel parameter to be specified just by itself,
without specifying any CPUs. This allows systems administrators to use
"rcu_nocbs" to specify that none of the CPUs are to be offloaded at boot
time, but than any of them may be offloaded at runtime via cpusets.
In contrast, if the "rcu_nocbs" or "nohz_full" kernel parameters are not
specified at all, then not only are none of the CPUs offloaded at boot,
none of them can be offloaded at runtime, either.
While in the area, modernize the description of the "rcuo" kthreads'
naming scheme.
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
In order to be able to (de-)offload any CPU using cpusets in the future,
create the NOCB data structures for all possible CPUs. For now this is
done only as long as the "rcu_nocbs=" or "nohz_full=" kernel parameters
are passed to avoid the unnecessary overhead for most users.
Note that the rcuog and rcuoc kthreads are not created until at least
one of the corresponding CPUs comes online. This approach avoids the
creation of excess kthreads when firmware lies about the number of CPUs
present on the system.
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently cpumask_available() is used to prevent from unwanted NOCB
initialization. However if neither "rcu_nocbs=" nor "nohz_full="
parameters are passed to a kernel built with CONFIG_CPUMASK_OFFSTACK=n,
the initialization path is still taken, running through all sorts of
needless operations and iterations on an empty cpumask.
Fix this by relying on a real initialization state instead. This also
optimizes kthread creation, preventing needless iteration over all online
CPUs when the kernel is booted without any offloaded CPUs.
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
In order to be able to toggle the offloaded state from cpusets, a nocb
kthread will need to be created for all possible CPUs whenever either
of the "rcu_nocbs=" or "nohz_full=" parameters are specified.
Therefore, the nocb_cb_wait() kthread must be prepared to start running
on a de-offloaded rdp. To accomplish this, simply move the sleeping
condition to the beginning of the nocb_cb_wait() function, which prevents
this kthread from attempting to invoke callbacks before the corresponding
CPU is offloaded.
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The nocb_gp_wait() function iterates over all CPUs in its group,
including even those CPUs that have been de-offloaded. This is of
course suboptimal, especially if none of the CPUs within the group are
currently offloaded. This will become even more of a problem once a
nocb kthread is created for all possible CPUs.
Therefore use a standard double linked list to link all the offloaded
rcu_data structures and safely add or delete these structure as we
offload or de-offload them, respectively.
Reviewed-by: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Uladzislau Rezki <urezki@gmail.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Joel Fernandes <joel@joelfernandes.org>
Tested-by: Juri Lelli <juri.lelli@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Pull networking fixes from Jakub Kicinski:
"Including fixes from bpf, can and netfilter.
Current release - regressions:
- bpf, sockmap: re-evaluate proto ops when psock is removed from
sockmap
Current release - new code bugs:
- bpf: fix bpf_check_mod_kfunc_call for built-in modules
- ice: fixes for TC classifier offloads
- vrf: don't run conntrack on vrf with !dflt qdisc
Previous releases - regressions:
- bpf: fix the off-by-two error in range markings
- seg6: fix the iif in the IPv6 socket control block
- devlink: fix netns refcount leak in devlink_nl_cmd_reload()
- dsa: mv88e6xxx: fix "don't use PHY_DETECT on internal PHY's"
- dsa: mv88e6xxx: allow use of PHYs on CPU and DSA ports
Previous releases - always broken:
- ethtool: do not perform operations on net devices being
unregistered
- udp: use datalen to cap max gso segments
- ice: fix races in stats collection
- fec: only clear interrupt of handling queue in fec_enet_rx_queue()
- m_can: pci: fix incorrect reference clock rate
- m_can: disable and ignore ELO interrupt
- mvpp2: fix XDP rx queues registering
Misc:
- treewide: add missing includes masked by cgroup -> bpf.h
dependency"
* tag 'net-5.16-rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (82 commits)
net: dsa: mv88e6xxx: allow use of PHYs on CPU and DSA ports
net: wwan: iosm: fixes unable to send AT command during mbim tx
net: wwan: iosm: fixes net interface nonfunctional after fw flash
net: wwan: iosm: fixes unnecessary doorbell send
net: dsa: felix: Fix memory leak in felix_setup_mmio_filtering
MAINTAINERS: s390/net: remove myself as maintainer
net/sched: fq_pie: prevent dismantle issue
net: mana: Fix memory leak in mana_hwc_create_wq
seg6: fix the iif in the IPv6 socket control block
nfp: Fix memory leak in nfp_cpp_area_cache_add()
nfc: fix potential NULL pointer deref in nfc_genl_dump_ses_done
nfc: fix segfault in nfc_genl_dump_devices_done
udp: using datalen to cap max gso segments
net: dsa: mv88e6xxx: error handling for serdes_power functions
can: kvaser_usb: get CAN clock frequency from device
can: kvaser_pciefd: kvaser_pciefd_rx_error_frame(): increase correct stats->{rx,tx}_errors counter
net: mvpp2: fix XDP rx queues registering
vmxnet3: fix minimum vectors alloc issue
net, neigh: clear whole pneigh_entry at alloc time
net: dsa: mv88e6xxx: fix "don't use PHY_DETECT on internal PHY's"
...
By default, when lock contention is encountered, the RCU Tasks flavors
of RCU switch to using per-CPU queueing. However, if the callback
flood ends, per-CPU queueing continues to be used, which introduces
significant additional overhead, especially for callback invocation,
which fans out a series of workqueue handlers.
This commit therefore switches back to single-queue operation if at the
beginning of a grace period there are very few callbacks. The definition
of "very few" is set by the rcupdate.rcu_task_collapse_lim module
parameter, which defaults to 10. This switch happens in two phases,
with the first phase causing future callbacks to be enqueued on CPU 0's
queue, but with all queues continuing to be checked for grace periods
and callback invocation. The second phase checks to see if an RCU grace
period has elapsed and if all remaining RCU-Tasks callbacks are queued
on CPU 0. If so, only CPU 0 is checked for future grace periods and
callback operation.
Of course, the return of contention anywhere during this process will
result in returning to per-CPU callback queueing.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Decreasing the number of callback queues is a bit tricky because it
is necessary to handle callbacks that were queued before the number of
queues decreased, but which were not ready to invoke until afterwards.
This commit takes a first step in this direction by maintaining a separate
->percpu_dequeue_lim to control callback dequeueing, in addition to the
existing ->percpu_enqueue_lim which now controls only enqueueing.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcupdate.rcu_task_enqueue_lim module parameter allows system
administrators to tune the number of callback queues used by the RCU
Tasks flavors. However if callback storms are infrequent, it would
be better to operate with a single queue on a given system unless and
until that system actually needed more queues. Systems not needing
more queues can then avoid the overhead of checking the extra queues
and especially avoid the overhead of fanning workqueue handlers out to
all CPUs to invoke callbacks.
This commit therefore switches to using all the CPUs' callback queues if
call_rcu_tasks_generic() encounters too much lock contention. The amount
of lock contention to tolerate defaults to 100 contended lock acquisitions
per jiffy, and can be adjusted using the new rcupdate.rcu_task_contend_lim
module parameter.
Such switching is undertaken only if the rcupdate.rcu_task_enqueue_lim
module parameter is negative, which is its default value (-1).
This allows savvy systems administrators to set the number of queues
to some known good value and to not have to worry about the kernel doing
any second guessing.
[ paulmck: Apply feedback from Guillaume Tucker and kernelci. ]
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If the caller of of call_rcu_tasks(), call_rcu_tasks_rude(),
or call_rcu_tasks_trace() holds a raw spinlock, and then if
call_rcu_tasks_generic() determines that the grace-period kthread must
be awakened, then the wakeup might acquire a normal spinlock while a
raw spinlock is held. This results in lockdep splats when the
kernel is built with CONFIG_PROVE_RAW_LOCK_NESTING=y.
This commit therefore defers the wakeup using irq_work_queue().
It would be nice to directly invoke wakeup when a raw spinlock is not
held, but there is currently no way to check for this in all kernels.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit converts the unconditional raw_spin_lock_rcu_node() lock
acquisition in call_rcu_tasks_generic() to a trylock followed by an
unconditional acquisition if the trylock fails. If the trylock fails,
the failure is counted, but the count is reset to zero on each new jiffy.
This statistic will be used to determine when to move from a single
callback queue to per-CPU callback queues.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a rcupdate.rcu_task_enqueue_lim module parameter that
sets the initial number of callback queues to use for the RCU Tasks
family of RCU implementations. This parameter allows testing of various
fanout values.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Currently, rcu_barrier_tasks(), rcu_barrier_tasks_rude(),
and rcu_barrier_tasks_trace() simply invoke the corresponding
synchronize_rcu_tasks*() function. This works because there is only
one callback queue.
However, there will soon be multiple callback queues. This commit
therefore scans the queues currently in use, entraining a callback on
each non-empty queue. Sequence numbers and reference counts are used
to synchronize this process in a manner similar to the approach taken
by rcu_barrier().
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
If there is a flood of callbacks, it is necessary to put multiple
CPUs to work invoking those callbacks. This commit therefore uses a
workqueue-flooding approach to parallelize RCU Tasks callback execution.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a rcu_tasks_invoke_cbs() function that invokes all
ready callbacks on all of the per-CPU lists that are currently in use.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit adds a rcu_tasks_need_gpcb() function that returns an
indication of whether another grace period is required, and if no grace
period is required, whether there are callbacks that need to be invoked.
The function scans all per-CPU lists currently in use.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Several ->poll() implementations are special in that they use a
waitqueue whose lifetime is the current task, rather than the struct
file as is normally the case. This is okay for blocking polls, since a
blocking poll occurs within one task; however, non-blocking polls
require another solution. This solution is for the queue to be cleared
before it is freed, using 'wake_up_poll(wq, EPOLLHUP | POLLFREE);'.
However, that has a bug: wake_up_poll() calls __wake_up() with
nr_exclusive=1. Therefore, if there are multiple "exclusive" waiters,
and the wakeup function for the first one returns a positive value, only
that one will be called. That's *not* what's needed for POLLFREE;
POLLFREE is special in that it really needs to wake up everyone.
Considering the three non-blocking poll systems:
- io_uring poll doesn't handle POLLFREE at all, so it is broken anyway.
- aio poll is unaffected, since it doesn't support exclusive waits.
However, that's fragile, as someone could add this feature later.
- epoll doesn't appear to be broken by this, since its wakeup function
returns 0 when it sees POLLFREE. But this is fragile.
Although there is a workaround (see epoll), it's better to define a
function which always sends POLLFREE to all waiters. Add such a
function. Also make it verify that the queue really becomes empty after
all waiters have been woken up.
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20211209010455.42744-2-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit adds a ->percpu_enqueue_lim field to the rcu_tasks structure.
This field contains two to the power of the ->percpu_enqueue_shift
field, easing construction of iterators over the per-CPU queues that
might contain RCU Tasks callbacks. Such iterators will be introduced
in later commits.
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit renames the rcu_tasks_percpu structure's ->cbs_pcpu_lock
to ->lock and then uses spin_lock_rcu_node() and friends to acquire and
release this lock, preparing for upcoming commits that will spread the
grace-period process across multiple CPUs and kthreads.
[ paulmck: Apply feedback from kernel test robot. ]
Reported-by: Martin Lau <kafai@fb.com>
Cc: Neeraj Upadhyay <neeraj.iitr10@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Daniel Borkmann says:
====================
bpf 2021-12-08
We've added 12 non-merge commits during the last 22 day(s) which contain
a total of 29 files changed, 659 insertions(+), 80 deletions(-).
The main changes are:
1) Fix an off-by-two error in packet range markings and also add a batch of
new tests for coverage of these corner cases, from Maxim Mikityanskiy.
2) Fix a compilation issue on MIPS JIT for R10000 CPUs, from Johan Almbladh.
3) Fix two functional regressions and a build warning related to BTF kfunc
for modules, from Kumar Kartikeya Dwivedi.
4) Fix outdated code and docs regarding BPF's migrate_disable() use on non-
PREEMPT_RT kernels, from Sebastian Andrzej Siewior.
5) Add missing includes in order to be able to detangle cgroup vs bpf header
dependencies, from Jakub Kicinski.
6) Fix regression in BPF sockmap tests caused by missing detachment of progs
from sockets when they are removed from the map, from John Fastabend.
7) Fix a missing "no previous prototype" warning in x86 JIT caused by BPF
dispatcher, from Björn Töpel.
* https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf:
bpf: Add selftests to cover packet access corner cases
bpf: Fix the off-by-two error in range markings
treewide: Add missing includes masked by cgroup -> bpf dependency
tools/resolve_btfids: Skip unresolved symbol warning for empty BTF sets
bpf: Fix bpf_check_mod_kfunc_call for built-in modules
bpf: Make CONFIG_DEBUG_INFO_BTF depend upon CONFIG_BPF_SYSCALL
mips, bpf: Fix reference to non-existing Kconfig symbol
bpf: Make sure bpf_disable_instrumentation() is safe vs preemption.
Documentation/locking/locktypes: Update migrate_disable() bits.
bpf, sockmap: Re-evaluate proto ops when psock is removed from sockmap
bpf, sockmap: Attach map progs to psock early for feature probes
bpf, x86: Fix "no previous prototype" warning
====================
Link: https://lore.kernel.org/r/20211208155125.11826-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
