Move the mutex waiter declaration from the public <linux/mutex.h> header
to the internal kernel/locking/mutex.h header.
There is no reason to expose it outside of the core code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211304.054325923@linutronix.de
Having two header files which contain just the non-debug and debug variants
is mostly waste of disc space and has no real value. Stick the debug
variants into the common mutex.h file as counterpart to the stubs for the
non-debug case.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.995350521@linutronix.de
Ensure all !RT tasks have the same prio such that they end up in FIFO
order and aren't split up according to nice level.
The reason why nice levels were taken into account so far is historical. In
the early days of the rtmutex code it was done to give the PI boosting and
deboosting a larger coverage.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.938676930@linutronix.de
Similar to rw_semaphores, on RT the rwlock substitution is not writer fair,
because it's not feasible to have a writer inherit its priority to
multiple readers. Readers blocked on a writer follow the normal rules of
priority inheritance. Like RT spinlocks, RT rwlocks are state preserving
across the slow lock operations (contended case).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.882793524@linutronix.de
Provide the actual locking functions which make use of the general and
spinlock specific rtmutex code.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.826621464@linutronix.de
A simplified version of the rtmutex slowlock function, which neither handles
signals nor timeouts, and is careful about preserving the state of the
blocked task across the lock operation.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.770228446@linutronix.de
Guard the regular sleeping lock specific functionality, which is used for
rtmutex on non-RT enabled kernels and for mutex, rtmutex and semaphores on
RT enabled kernels so the code can be reused for the RT specific
implementation of spinlocks and rwlocks in a different compilation unit.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.311535693@linutronix.de
Add an rtlock_task pointer to rt_mutex_wake_q, which allows to handle the RT
specific wakeup for spin/rwlock waiters. The pointer is just consuming 4/8
bytes on the stack so it is provided unconditionaly to avoid #ifdeffery all
over the place.
This cannot use a regular wake_q, because a task can have concurrent wakeups which
would make it miss either lock or the regular wakeups, depending on what gets
queued first, unless task struct gains a separate wake_q_node for this, which
would be overkill, because there can only be a single task which gets woken
up in the spin/rw_lock unlock path.
No functional change for non-RT enabled kernels.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.253614678@linutronix.de
Prepare for the required state aware handling of waiter wakeups via wake_q
and switch the rtmutex code over to the rtmutex specific wrapper.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.197113263@linutronix.de
To handle the difference between wakeups for regular sleeping locks (mutex,
rtmutex, rw_semaphore) and the wakeups for 'sleeping' spin/rwlocks on
PREEMPT_RT enabled kernels correctly, it is required to provide a
wake_q_head construct which allows to keep them separate.
Provide a wrapper around wake_q_head and the required helpers, which will be
extended with the state handling later.
No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.139337655@linutronix.de
Regular sleeping locks like mutexes, rtmutexes and rw_semaphores are always
entering and leaving a blocking section with task state == TASK_RUNNING.
On a non-RT kernel spinlocks and rwlocks never affect the task state, but
on RT kernels these locks are converted to rtmutex based 'sleeping' locks.
So in case of contention the task goes to block, which requires to carefully
preserve the task state, and restore it after acquiring the lock taking
regular wakeups for the task into account, which happened while the task was
blocked. This state preserving is achieved by having a separate task state
for blocking on a RT spin/rwlock and a saved_state field in task_struct
along with careful handling of these wakeup scenarios in try_to_wake_up().
To avoid conditionals in the rtmutex code, store the wake state which has
to be used for waking a lock waiter in rt_mutex_waiter which allows to
handle the regular and RT spin/rwlocks by handing it to wake_up_state().
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.079800739@linutronix.de
The RT specific R/W semaphore implementation used to restrict the number of
readers to one, because a writer cannot block on multiple readers and
inherit its priority or budget.
The single reader restricting was painful in various ways:
- Performance bottleneck for multi-threaded applications in the page fault
path (mmap sem)
- Progress blocker for drivers which are carefully crafted to avoid the
potential reader/writer deadlock in mainline.
The analysis of the writer code paths shows that properly written RT tasks
should not take them. Syscalls like mmap(), file access which take mmap sem
write locked have unbound latencies, which are completely unrelated to mmap
sem. Other R/W sem users like graphics drivers are not suitable for RT tasks
either.
So there is little risk to hurt RT tasks when the RT rwsem implementation is
done in the following way:
- Allow concurrent readers
- Make writers block until the last reader left the critical section. This
blocking is not subject to priority/budget inheritance.
- Readers blocked on a writer inherit their priority/budget in the normal
way.
There is a drawback with this scheme: R/W semaphores become writer unfair
though the applications which have triggered writer starvation (mostly on
mmap_sem) in the past are not really the typical workloads running on a RT
system. So while it's unlikely to hit writer starvation, it's possible. If
there are unexpected workloads on RT systems triggering it, the problem
has to be revisited.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211303.016885947@linutronix.de
On PREEMPT_RT, rw_semaphores and rwlocks are substituted with an rtmutex and
a reader count. The implementation is writer unfair, as it is not feasible
to do priority inheritance on multiple readers, but experience has shown
that real-time workloads are not the typical workloads which are sensitive
to writer starvation.
The inner workings of rw_semaphores and rwlocks on RT are almost identical
except for the task state and signal handling. rw_semaphores are not state
preserving over a contention, they are expected to enter and leave with state
== TASK_RUNNING. rwlocks have a mechanism to preserve the state of the task
at entry and restore it after unblocking taking potential non-lock related
wakeups into account. rw_semaphores can also be subject to signal handling
interrupting a blocked state, while rwlocks ignore signals.
To avoid code duplication, provide a shared implementation which takes the
small difference vs. state and signals into account. The code is included
into the relevant rw_semaphore/rwlock base code and compiled for each use
case separately.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.957920571@linutronix.de
Split the inner workings of rt_mutex_slowlock() out into a separate
function, which can be reused by the upcoming RT lock substitutions,
e.g. for rw_semaphores.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.841971086@linutronix.de
RT builds substitutions for rwsem, mutex, spinlock and rwlock around
rtmutexes. Split the inner working out so each lock substitution can use
them with the appropriate lockdep annotations. This avoids having an extra
unused lockdep map in the wrapped rtmutex.
No functional change.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.784739994@linutronix.de
Prepare for reusing the inner functions of rtmutex for RT lock
substitutions: introduce kernel/locking/rtmutex_api.c and move
them there.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.726560996@linutronix.de
Allows the compiler to generate better code depending on the architecture.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.668958502@linutronix.de
Inlines are type-safe...
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.610830960@linutronix.de
RT mutexes belong to the LD_WAIT_SLEEP class. Make them so.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211302.031014562@linutronix.de
The 2nd parameter 'count' is not used in this function.
The places where the function is called are also modified.
Signed-off-by: xuyehan <xuyehan@xiaomi.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/1625547043-28103-1-git-send-email-yehanxu1@gmail.com
Yanfei reported that it is possible to loose HANDOFF when we race with
mutex_unlock() and end up setting HANDOFF on an unlocked mutex. At
that point anybody can steal it, losing HANDOFF in the process.
If this happens often enough, we can in fact starve the top waiter.
Solve this by folding the 'set HANDOFF' operation into the trylock
operation, such that either we acquire the lock, or it gets HANDOFF
set. This avoids having HANDOFF set on an unlocked mutex.
Reported-by: Yanfei Xu <yanfei.xu@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Waiman Long <longman@redhat.com>
Reviewed-by: Yanfei Xu <yanfei.xu@windriver.com>
Link: https://lore.kernel.org/r/20210630154114.958507900@infradead.org
Yanfei reported that setting HANDOFF should not depend on recomputing
@first, only on @first state. Which would then give:
if (ww_ctx || !first)
first = __mutex_waiter_is_first(lock, &waiter);
if (first)
__mutex_set_flag(lock, MUTEX_FLAG_HANDOFF);
But because 'ww_ctx || !first' is basically 'always' and the test for
first is relatively cheap, omit that first branch entirely.
Reported-by: Yanfei Xu <yanfei.xu@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Waiman Long <longman@redhat.com>
Reviewed-by: Yanfei Xu <yanfei.xu@windriver.com>
Link: https://lore.kernel.org/r/20210630154114.896786297@infradead.org
When enabling CONFIG_LOCK_STAT=y, then CONFIG_LOCKDEP=y is forcedly enabled,
but CONFIG_PROVE_LOCKING is disabled.
We can get output from /proc/lockdep, which currently includes usages of
lock classes. But the usages are meaningless, see the output below:
/ # cat /proc/lockdep
all lock classes:
ffffffff9af63350 ....: cgroup_mutex
ffffffff9af54eb8 ....: (console_sem).lock
ffffffff9af54e60 ....: console_lock
ffffffff9ae74c38 ....: console_owner_lock
ffffffff9ae74c80 ....: console_owner
ffffffff9ae66e60 ....: cpu_hotplug_lock
Only one usage context for each lock, this is because each usage is only
changed in mark_lock() that is in the CONFIG_PROVE_LOCKING=y section,
however in the test situation, it's not.
The fix is to move the usages reading and seq_print from the
!CONFIG_PROVE_LOCKING section to its defined section.
Also, locks_after list of lock_class is empty when !CONFIG_PROVE_LOCKING,
so do the same thing as what have done for usages of lock classes.
With this patch with !CONFIG_PROVE_LOCKING we can get the results below:
/ # cat /proc/lockdep
all lock classes:
ffffffff85163290: cgroup_mutex
ffffffff85154dd8: (console_sem).lock
ffffffff85154d80: console_lock
ffffffff85074b58: console_owner_lock
ffffffff85074ba0: console_owner
ffffffff85066d60: cpu_hotplug_lock
... a class key and the relevant class name each line.
Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20210629135916.308210-1-sxwjean@me.com
Pull RCU updates from Paul McKenney:
- Bitmap parsing support for "all" as an alias for all bits
- Documentation updates
- Miscellaneous fixes, including some that overlap into mm and lockdep
- kvfree_rcu() updates
- mem_dump_obj() updates, with acks from one of the slab-allocator
maintainers
- RCU NOCB CPU updates, including limited deoffloading
- SRCU updates
- Tasks-RCU updates
- Torture-test updates
* 'core-rcu-2021.07.04' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (78 commits)
tasks-rcu: Make show_rcu_tasks_gp_kthreads() be static inline
rcu-tasks: Make ksoftirqd provide RCU Tasks quiescent states
rcu: Add missing __releases() annotation
rcu: Remove obsolete rcu_read_unlock() deadlock commentary
rcu: Improve comments describing RCU read-side critical sections
rcu: Create an unrcu_pointer() to remove __rcu from a pointer
srcu: Early test SRCU polling start
rcu: Fix various typos in comments
rcu/nocb: Unify timers
rcu/nocb: Prepare for fine-grained deferred wakeup
rcu/nocb: Only cancel nocb timer if not polling
rcu/nocb: Delete bypass_timer upon nocb_gp wakeup
rcu/nocb: Cancel nocb_timer upon nocb_gp wakeup
rcu/nocb: Allow de-offloading rdp leader
rcu/nocb: Directly call __wake_nocb_gp() from bypass timer
rcu: Don't penalize priority boosting when there is nothing to boost
rcu: Point to documentation of ordering guarantees
rcu: Make rcu_gp_cleanup() be noinline for tracing
rcu: Restrict RCU_STRICT_GRACE_PERIOD to at most four CPUs
rcu: Make show_rcu_gp_kthreads() dump rcu_node structures blocking GP
...
- Changes to core scheduling facilities:
- Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables
coordinated scheduling across SMT siblings. This is a much
requested feature for cloud computing platforms, to allow
the flexible utilization of SMT siblings, without exposing
untrusted domains to information leaks & side channels, plus
to ensure more deterministic computing performance on SMT
systems used by heterogenous workloads.
There's new prctls to set core scheduling groups, which
allows more flexible management of workloads that can share
siblings.
- Fix task->state access anti-patterns that may result in missed
wakeups and rename it to ->__state in the process to catch new
abuses.
- Load-balancing changes:
- Tweak newidle_balance for fair-sched, to improve
'memcache'-like workloads.
- "Age" (decay) average idle time, to better track & improve workloads
such as 'tbench'.
- Fix & improve energy-aware (EAS) balancing logic & metrics.
- Fix & improve the uclamp metrics.
- Fix task migration (taskset) corner case on !CONFIG_CPUSET.
- Fix RT and deadline utilization tracking across policy changes
- Introduce a "burstable" CFS controller via cgroups, which allows
bursty CPU-bound workloads to borrow a bit against their future
quota to improve overall latencies & batching. Can be tweaked
via /sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us.
- Rework assymetric topology/capacity detection & handling.
- Scheduler statistics & tooling:
- Disable delayacct by default, but add a sysctl to enable
it at runtime if tooling needs it. Use static keys and
other optimizations to make it more palatable.
- Use sched_clock() in delayacct, instead of ktime_get_ns().
- Misc cleanups and fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-----BEGIN PGP SIGNATURE-----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=3VDr
-----END PGP SIGNATURE-----
Merge tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler udpates from Ingo Molnar:
- Changes to core scheduling facilities:
- Add "Core Scheduling" via CONFIG_SCHED_CORE=y, which enables
coordinated scheduling across SMT siblings. This is a much
requested feature for cloud computing platforms, to allow the
flexible utilization of SMT siblings, without exposing untrusted
domains to information leaks & side channels, plus to ensure more
deterministic computing performance on SMT systems used by
heterogenous workloads.
There are new prctls to set core scheduling groups, which allows
more flexible management of workloads that can share siblings.
- Fix task->state access anti-patterns that may result in missed
wakeups and rename it to ->__state in the process to catch new
abuses.
- Load-balancing changes:
- Tweak newidle_balance for fair-sched, to improve 'memcache'-like
workloads.
- "Age" (decay) average idle time, to better track & improve
workloads such as 'tbench'.
- Fix & improve energy-aware (EAS) balancing logic & metrics.
- Fix & improve the uclamp metrics.
- Fix task migration (taskset) corner case on !CONFIG_CPUSET.
- Fix RT and deadline utilization tracking across policy changes
- Introduce a "burstable" CFS controller via cgroups, which allows
bursty CPU-bound workloads to borrow a bit against their future
quota to improve overall latencies & batching. Can be tweaked via
/sys/fs/cgroup/cpu/<X>/cpu.cfs_burst_us.
- Rework assymetric topology/capacity detection & handling.
- Scheduler statistics & tooling:
- Disable delayacct by default, but add a sysctl to enable it at
runtime if tooling needs it. Use static keys and other
optimizations to make it more palatable.
- Use sched_clock() in delayacct, instead of ktime_get_ns().
- Misc cleanups and fixes.
* tag 'sched-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (72 commits)
sched/doc: Update the CPU capacity asymmetry bits
sched/topology: Rework CPU capacity asymmetry detection
sched/core: Introduce SD_ASYM_CPUCAPACITY_FULL sched_domain flag
psi: Fix race between psi_trigger_create/destroy
sched/fair: Introduce the burstable CFS controller
sched/uclamp: Fix uclamp_tg_restrict()
sched/rt: Fix Deadline utilization tracking during policy change
sched/rt: Fix RT utilization tracking during policy change
sched: Change task_struct::state
sched,arch: Remove unused TASK_STATE offsets
sched,timer: Use __set_current_state()
sched: Add get_current_state()
sched,perf,kvm: Fix preemption condition
sched: Introduce task_is_running()
sched: Unbreak wakeups
sched/fair: Age the average idle time
sched/cpufreq: Consider reduced CPU capacity in energy calculation
sched/fair: Take thermal pressure into account while estimating energy
thermal/cpufreq_cooling: Update offline CPUs per-cpu thermal_pressure
sched/fair: Return early from update_tg_cfs_load() if delta == 0
...
- Core locking & atomics:
- Convert all architectures to ARCH_ATOMIC: move every
architecture to ARCH_ATOMIC, then get rid of ARCH_ATOMIC
and all the transitory facilities and #ifdefs.
Much reduction in complexity from that series:
63 files changed, 756 insertions(+), 4094 deletions(-)
- Self-test enhancements
- Futexes:
- Add the new FUTEX_LOCK_PI2 ABI, which is a variant that
doesn't set FLAGS_CLOCKRT (.e. uses CLOCK_MONOTONIC).
[ The temptation to repurpose FUTEX_LOCK_PI's implicit
setting of FLAGS_CLOCKRT & invert the flag's meaning
to avoid having to introduce a new variant was
resisted successfully. ]
- Enhance futex self-tests
- Lockdep:
- Fix dependency path printouts
- Optimize trace saving
- Broaden & fix wait-context checks
- Misc cleanups and fixes.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-----BEGIN PGP SIGNATURE-----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=tH//
-----END PGP SIGNATURE-----
Merge tag 'locking-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
- Core locking & atomics:
- Convert all architectures to ARCH_ATOMIC: move every architecture
to ARCH_ATOMIC, then get rid of ARCH_ATOMIC and all the
transitory facilities and #ifdefs.
Much reduction in complexity from that series:
63 files changed, 756 insertions(+), 4094 deletions(-)
- Self-test enhancements
- Futexes:
- Add the new FUTEX_LOCK_PI2 ABI, which is a variant that doesn't
set FLAGS_CLOCKRT (.e. uses CLOCK_MONOTONIC).
[ The temptation to repurpose FUTEX_LOCK_PI's implicit setting of
FLAGS_CLOCKRT & invert the flag's meaning to avoid having to
introduce a new variant was resisted successfully. ]
- Enhance futex self-tests
- Lockdep:
- Fix dependency path printouts
- Optimize trace saving
- Broaden & fix wait-context checks
- Misc cleanups and fixes.
* tag 'locking-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
locking/lockdep: Correct the description error for check_redundant()
futex: Provide FUTEX_LOCK_PI2 to support clock selection
futex: Prepare futex_lock_pi() for runtime clock selection
lockdep/selftest: Remove wait-type RCU_CALLBACK tests
lockdep/selftests: Fix selftests vs PROVE_RAW_LOCK_NESTING
lockdep: Fix wait-type for empty stack
locking/selftests: Add a selftest for check_irq_usage()
lockding/lockdep: Avoid to find wrong lock dep path in check_irq_usage()
locking/lockdep: Remove the unnecessary trace saving
locking/lockdep: Fix the dep path printing for backwards BFS
selftests: futex: Add futex compare requeue test
selftests: futex: Add futex wait test
seqlock: Remove trailing semicolon in macros
locking/lockdep: Reduce LOCKDEP dependency list
locking/lockdep,doc: Improve readability of the block matrix
locking/atomics: atomic-instrumented: simplify ifdeffery
locking/atomic: delete !ARCH_ATOMIC remnants
locking/atomic: xtensa: move to ARCH_ATOMIC
locking/atomic: sparc: move to ARCH_ATOMIC
locking/atomic: sh: move to ARCH_ATOMIC
...
If there is no matched result, check_redundant() will return BFS_RNOMATCH.
Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lkml.kernel.org/r/20210618130230.123249-1-sxwjean@me.com
Even the very first lock can violate the wait-context check, consider
the various IRQ contexts.
Fixes: de8f5e4f2d ("lockdep: Introduce wait-type checks")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20210617190313.256987481@infradead.org
In the step #3 of check_irq_usage(), we seach backwards to find a lock
whose usage conflicts the usage of @target_entry1 on safe/unsafe.
However, we should only keep the irq-unsafe usage of @target_entry1 into
consideration, because it could be a case where a lock is hardirq-unsafe
but soft-safe, and in check_irq_usage() we find it because its
hardirq-unsafe could result into a hardirq-safe-unsafe deadlock, but
currently since we don't filter out the other usage bits, so we may find
a lock dependency path softirq-unsafe -> softirq-safe, which in fact
doesn't cause a deadlock. And this may cause misleading lockdep splats.
Fix this by only keeping LOCKF_ENABLED_IRQ_ALL bits when we try the
backwards search.
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210618170110.3699115-4-boqun.feng@gmail.com
In print_bad_irq_dependency(), save_trace() is called to set the ->trace
for @prev_root as the current call trace, however @prev_root corresponds
to the the held lock, which may not be acquired in current call trace,
therefore it's wrong to use save_trace() to set ->trace of @prev_root.
Moreover, with our adjustment of printing backwards dependency path, the
->trace of @prev_root is unncessary, so remove it.
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210618170110.3699115-3-boqun.feng@gmail.com
We use the same code to print backwards lock dependency path as the
forwards lock dependency path, and this could result into incorrect
printing because for a backwards lock_list ->trace is not the call trace
where the lock of ->class is acquired.
Fix this by introducing a separate function on printing the backwards
dependency path. Also add a few comments about the printing while we are
at it.
Reported-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210618170110.3699115-2-boqun.feng@gmail.com
Change the type and name of task_struct::state. Drop the volatile and
shrink it to an 'unsigned int'. Rename it in order to find all uses
such that we can use READ_ONCE/WRITE_ONCE as appropriate.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20210611082838.550736351@infradead.org
Replace a bunch of 'p->state == TASK_RUNNING' with a new helper:
task_is_running(p).
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.222401495@infradead.org
When a interruptible mutex locker is interrupted by a signal
without acquiring this lock and removed from the wait queue.
if the mutex isn't contended enough to have a waiter
put into the wait queue again, the setting of the WAITER
bit will force mutex locker to go into the slowpath to
acquire the lock every time, so if the wait queue is empty,
the WAITER bit need to be clear.
Fixes: 040a0a3710 ("mutex: Add support for wound/wait style locks")
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Zqiang <qiang.zhang@windriver.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210517034005.30828-1-qiang.zhang@windriver.com
The reason that lockdep_rcu_suspicious() prints the value of debug_locks
is because a value of zero indicates a likely false positive. This can
work, but is a bit obtuse. This commit therefore explicitly calls out
the possibility of a false positive.
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Make the code more readable by replacing the atomic_cmpxchg_acquire()
by an equivalent atomic_try_cmpxchg_acquire() and change atomic_add()
to atomic_or().
For architectures that use qrwlock, I do not find one that has an
atomic_add() defined but not an atomic_or(). I guess it should be fine
by changing atomic_add() to atomic_or().
Note that the previous use of atomic_add() isn't wrong as only one
writer that is the wait_lock owner can set the waiting flag and the
flag will be cleared later on when acquiring the write lock.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20210426185017.19815-1-longman@redhat.com
- rtmutex cleanup & spring cleaning pass that removes ~400 lines of code
- Futex simplifications & cleanups
- Add debugging to the CSD code, to help track down a tenacious race (or hw problem)
- Add lockdep_assert_not_held(), to allow code to require a lock to not be held,
and propagate this into the ath10k driver
- Misc LKMM documentation updates
- Misc KCSAN updates: cleanups & documentation updates
- Misc fixes and cleanups
- Fix locktorture bugs with ww_mutexes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-----BEGIN PGP SIGNATURE-----
iQJFBAABCgAvFiEEBpT5eoXrXCwVQwEKEnMQ0APhK1gFAmCJDn0RHG1pbmdvQGtl
cm5lbC5vcmcACgkQEnMQ0APhK1hPrRAAryS4zPnuDsfkVk0smxo7a0lK5ljbH2Xo
28QUZXOl6upnEV8dzbjwG7eAjt5ZJVI5tKIeG0PV0NUJH2nsyHwESdtULGGYuPf/
4YUzNwZJa+nI/jeBnVsXCimLVxxnNCRdR7yOVOHm4ukEwa+YTNt1pvlYRmUd4YyH
Q5cCrpb3THvLka3AAamEbqnHnAdGxHKuuHYVRkODpMQ+zrQvtN8antYsuk8kJsqM
m+GZg/dVCuLEPah5k+lOACtcq/w7HCmTlxS8t4XLvD52jywFZLcCPvi1rk0+JR+k
Vd9TngC09GJ4jXuDpr42YKkU9/X6qy2Es39iA/ozCvc1Alrhspx/59XmaVSuWQGo
XYuEPx38Yuo/6w16haSgp0k4WSay15A4uhCTQ75VF4vli8Bqgg9PaxLyQH1uG8e2
xk8U90R7bDzLlhKYIx1Vu5Z0t7A1JtB5CJtgpcfg/zQLlzygo75fHzdAiU5fDBDm
3QQXSU2Oqzt7c5ZypioHWazARk7tL6th38KGN1gZDTm5zwifpaCtHi7sml6hhZ/4
ATH6zEPzIbXJL2UqumSli6H4ye5ORNjOu32r7YPqLI4IDbzpssfoSwfKYlQG4Tvn
4H1Ukirzni0gz5+wbleItzf2aeo1rocs4YQTnaT02j8NmUHUz4AzOHGOQFr5Tvh0
wk/P4MIoSb0=
=cOOk
-----END PGP SIGNATURE-----
Merge tag 'locking-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Ingo Molnar:
- rtmutex cleanup & spring cleaning pass that removes ~400 lines of
code
- Futex simplifications & cleanups
- Add debugging to the CSD code, to help track down a tenacious race
(or hw problem)
- Add lockdep_assert_not_held(), to allow code to require a lock to not
be held, and propagate this into the ath10k driver
- Misc LKMM documentation updates
- Misc KCSAN updates: cleanups & documentation updates
- Misc fixes and cleanups
- Fix locktorture bugs with ww_mutexes
* tag 'locking-core-2021-04-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (44 commits)
kcsan: Fix printk format string
static_call: Relax static_call_update() function argument type
static_call: Fix unused variable warn w/o MODULE
locking/rtmutex: Clean up signal handling in __rt_mutex_slowlock()
locking/rtmutex: Restrict the trylock WARN_ON() to debug
locking/rtmutex: Fix misleading comment in rt_mutex_postunlock()
locking/rtmutex: Consolidate the fast/slowpath invocation
locking/rtmutex: Make text section and inlining consistent
locking/rtmutex: Move debug functions as inlines into common header
locking/rtmutex: Decrapify __rt_mutex_init()
locking/rtmutex: Remove pointless CONFIG_RT_MUTEXES=n stubs
locking/rtmutex: Inline chainwalk depth check
locking/rtmutex: Move rt_mutex_debug_task_free() to rtmutex.c
locking/rtmutex: Remove empty and unused debug stubs
locking/rtmutex: Consolidate rt_mutex_init()
locking/rtmutex: Remove output from deadlock detector
locking/rtmutex: Remove rtmutex deadlock tester leftovers
locking/rtmutex: Remove rt_mutex_timed_lock()
MAINTAINERS: Add myself as futex reviewer
locking/mutex: Remove repeated declaration
...
Peter Zijlstra asked us to find bad annotation that blows up the lockdep
storage [1][2][3] but we could not find such annotation [4][5], and
Peter cannot give us feedback any more [6]. Since we tested this patch
on linux-next.git without problems, and keeping this problem unresolved
discourages kernel testing which is more painful, I'm sending this patch
without forever waiting for response from Peter.
[1] https://lkml.kernel.org/r/20200916115057.GO2674@hirez.programming.kicks-ass.net
[2] https://lkml.kernel.org/r/20201118142357.GW3121392@hirez.programming.kicks-ass.net
[3] https://lkml.kernel.org/r/20201118151038.GX3121392@hirez.programming.kicks-ass.net
[4] https://lkml.kernel.org/r/CACT4Y+asqRbjaN9ras=P5DcxKgzsnV0fvV0tYb2VkT+P00pFvQ@mail.gmail.com
[5] https://lkml.kernel.org/r/4b89985e-99f9-18bc-0bf1-c883127dc70c@i-love.sakura.ne.jp
[6] https://lkml.kernel.org/r/CACT4Y+YnHFV1p5mbhby2nyOaNTy8c_yoVk86z5avo14KWs0s1A@mail.gmail.com
kernel/locking/lockdep.c | 2 -
kernel/locking/lockdep_internals.h | 8 +++----
lib/Kconfig.debug | 40 +++++++++++++++++++++++++++++++++++++
3 files changed, 45 insertions(+), 5 deletions(-)
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.22 (GNU/Linux)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=E7U/
-----END PGP SIGNATURE-----
Merge tag 'tomoyo-pr-20210426' of git://git.osdn.net/gitroot/tomoyo/tomoyo-test1
Pull lockdep capacity limit updates from Tetsuo Handa:
"syzbot is occasionally reporting that fuzz testing is terminated due
to hitting upper limits lockdep can track.
Analysis via /proc/lockdep* did not show any obvious culprits, allow
tuning tracing capacity constants"
* tag 'tomoyo-pr-20210426' of git://git.osdn.net/gitroot/tomoyo/tomoyo-test1:
lockdep: Allow tuning tracing capacity constants.
While this code is executed with the wait_lock held, a reader can
acquire the lock without holding wait_lock. The writer side loops
checking the value with the atomic_cond_read_acquire(), but only truly
acquires the lock when the compare-and-exchange is completed
successfully which isn’t ordered. This exposes the window between the
acquire and the cmpxchg to an A-B-A problem which allows reads
following the lock acquisition to observe values speculatively before
the write lock is truly acquired.
We've seen a problem in epoll where the reader does a xchg while
holding the read lock, but the writer can see a value change out from
under it.
Writer | Reader
--------------------------------------------------------------------------------
ep_scan_ready_list() |
|- write_lock_irq() |
|- queued_write_lock_slowpath() |
|- atomic_cond_read_acquire() |
| read_lock_irqsave(&ep->lock, flags);
--> (observes value before unlock) | chain_epi_lockless()
| | epi->next = xchg(&ep->ovflist, epi);
| | read_unlock_irqrestore(&ep->lock, flags);
| |
| atomic_cmpxchg_relaxed() |
|-- READ_ONCE(ep->ovflist); |
A core can order the read of the ovflist ahead of the
atomic_cmpxchg_relaxed(). Switching the cmpxchg to use acquire
semantics addresses this issue at which point the atomic_cond_read can
be switched to use relaxed semantics.
Fixes: b519b56e37 ("locking/qrwlock: Use atomic_cond_read_acquire() when spinning in qrwlock")
Signed-off-by: Ali Saidi <alisaidi@amazon.com>
[peterz: use try_cmpxchg()]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Steve Capper <steve.capper@arm.com>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Waiman Long <longman@redhat.com>
Tested-by: Steve Capper <steve.capper@arm.com>
ambiguous/confusing kernel log message.
Signed-off-by: Ingo Molnar <mingo@kernel.org>
-----BEGIN PGP SIGNATURE-----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=y7/k
-----END PGP SIGNATURE-----
Merge tag 'locking-urgent-2021-04-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixlets from Ingo Molnar:
"Two minor fixes: one for a Clang warning, the other improves an
ambiguous/confusing kernel log message"
* tag 'locking-urgent-2021-04-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
lockdep: Address clang -Wformat warning printing for %hd
lockdep: Add a missing initialization hint to the "INFO: Trying to register non-static key" message
The signal handling in __rt_mutex_slowlock() is open coded.
Use signal_pending_state() instead.
Aside of the cleanup this also prepares for the RT lock substituions which
require support for TASK_KILLABLE.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210326153944.533811987@linutronix.de
The warning as written is expensive and not really required for a
production kernel. Make it depend on rt mutex debugging and use !in_task()
for the condition which generates far better code and gives the same
answer.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210326153944.436565064@linutronix.de
