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| author | Peter Zijlstra <peterz@infradead.org> | 2019-08-26 10:31:14 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-09-06 10:23:28 +0200 |
| commit | eeb6b4a09695ee4ddc7147918d2e2cccef556ca9 (patch) | |
| tree | 28ac2ea7db379564939453fbf8918bb832346760 /kernel | |
| parent | 931424d0781ea980d81c8d848a3a78dd9ed8885b (diff) | |
| download | linux-stable-eeb6b4a09695ee4ddc7147918d2e2cccef556ca9.tar.gz linux-stable-eeb6b4a09695ee4ddc7147918d2e2cccef556ca9.tar.bz2 linux-stable-eeb6b4a09695ee4ddc7147918d2e2cccef556ca9.zip | |
lcoking/rwsem: Add missing ACQUIRE to read_slowpath sleep loop
[ Upstream commit 99143f82a255e7f054bead8443462fae76dd829e ]
While reviewing another read_slowpath patch, both Will and I noticed
another missing ACQUIRE, namely:
X = 0;
CPU0 CPU1
rwsem_down_read()
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
X = 1;
rwsem_up_write();
rwsem_mark_wake()
atomic_long_add(adjustment, &sem->count);
smp_store_release(&waiter->task, NULL);
if (!waiter.task)
break;
...
}
r = X;
Allows 'r == 0'.
Reported-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reported-by: Will Deacon <will@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/rwsem-xadd.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 397dedc58432..385ebcfc31a6 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -485,8 +485,10 @@ __rwsem_down_read_failed_common(struct rw_semaphore *sem, int state) /* wait to be given the lock */ while (true) { set_current_state(state); - if (!waiter.task) + if (!smp_load_acquire(&waiter.task)) { + /* Orders against rwsem_mark_wake()'s smp_store_release() */ break; + } if (signal_pending_state(state, current)) { raw_spin_lock_irq(&sem->wait_lock); if (waiter.task) |