diff options
| author | Namhyung Kim <namhyung@kernel.org> | 2023-11-08 13:53:22 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2024-02-28 13:10:29 +0100 |
| commit | f3e3620f1a97fcd02a5f3606fa63888dbcffd82c (patch) | |
| tree | d6bc4500d2847de87746c9926448c9e0ac3dbb8b /kernel/locking/percpu-rwsem.c | |
| parent | f22f71322a18e90e127f2fc2c11cc2d5191bc4c6 (diff) | |
locking/percpu-rwsem: Trigger contention tracepoints only if contended
We mistakenly always fire lock contention tracepoints in the writer path,
while it should be conditional on the trylock result.
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20231108215322.2845536-1-namhyung@kernel.org
Diffstat (limited to 'kernel/locking/percpu-rwsem.c')
| -rw-r--r-- | kernel/locking/percpu-rwsem.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 185bd1c906b0..6083883c4fe0 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -223,9 +223,10 @@ static bool readers_active_check(struct percpu_rw_semaphore *sem) void __sched percpu_down_write(struct percpu_rw_semaphore *sem) { + bool contended = false; + might_sleep(); rwsem_acquire(&sem->dep_map, 0, 0, _RET_IP_); - trace_contention_begin(sem, LCB_F_PERCPU | LCB_F_WRITE); /* Notify readers to take the slow path. */ rcu_sync_enter(&sem->rss); @@ -234,8 +235,11 @@ void __sched percpu_down_write(struct percpu_rw_semaphore *sem) * Try set sem->block; this provides writer-writer exclusion. * Having sem->block set makes new readers block. */ - if (!__percpu_down_write_trylock(sem)) + if (!__percpu_down_write_trylock(sem)) { + trace_contention_begin(sem, LCB_F_PERCPU | LCB_F_WRITE); percpu_rwsem_wait(sem, /* .reader = */ false); + contended = true; + } /* smp_mb() implied by __percpu_down_write_trylock() on success -- D matches A */ @@ -247,7 +251,8 @@ void __sched percpu_down_write(struct percpu_rw_semaphore *sem) /* Wait for all active readers to complete. */ rcuwait_wait_event(&sem->writer, readers_active_check(sem), TASK_UNINTERRUPTIBLE); - trace_contention_end(sem, 0); + if (contended) + trace_contention_end(sem, 0); } EXPORT_SYMBOL_GPL(percpu_down_write); |