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authorPeter Zijlstra <peterz@infradead.org>2019-07-18 14:56:17 +0200
committerIngo Molnar <mingo@kernel.org>2019-07-25 15:39:24 +0200
commit99143f82a255e7f054bead8443462fae76dd829e (patch)
treefb581b5301b554d40903c234e22ffab3b21b774b /kernel
parente1b98fa316648420d0434d9ff5b92ad6609ba6c3 (diff)
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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.c4
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)