diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2019-07-18 14:56:17 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2019-07-25 15:39:24 +0200 |
| commit | 99143f82a255e7f054bead8443462fae76dd829e (patch) | |
| tree | fb581b5301b554d40903c234e22ffab3b21b774b /kernel | |
| parent | e1b98fa316648420d0434d9ff5b92ad6609ba6c3 (diff) | |
| download | lwn-99143f82a255e7f054bead8443462fae76dd829e.tar.gz lwn-99143f82a255e7f054bead8443462fae76dd829e.zip | |
lcoking/rwsem: Add missing ACQUIRE to read_slowpath sleep loop
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>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/rwsem.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index d3ce7c6c42a6..571938887cc8 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -1073,8 +1073,10 @@ queue: /* 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) |