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authorLinus Torvalds <torvalds@linux-foundation.org>2021-04-25 09:10:10 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-04-25 09:10:10 -0700
commit0146da0d4cecad571f69f02fe35d75d6dba9723c (patch)
treeaa30f42b243acbe518d7e8189a5bf206a002f43d
parent682b26bd80f96c2e4da3eb6dcec8bf684b79151c (diff)
parent84a24bf8c52e66b7ac89ada5e3cfbe72d65c1896 (diff)
Merge tag 'locking_urgent_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fix from Borislav Petkov: "Fix ordering in the queued writer lock's slowpath" * tag 'locking_urgent_for_v5.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: locking/qrwlock: Fix ordering in queued_write_lock_slowpath()
-rw-r--r--kernel/locking/qrwlock.c7
1 files changed, 4 insertions, 3 deletions
diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c
index 4786dd271b45..b94f3831e963 100644
--- a/kernel/locking/qrwlock.c
+++ b/kernel/locking/qrwlock.c
@@ -60,6 +60,8 @@ EXPORT_SYMBOL(queued_read_lock_slowpath);
*/
void queued_write_lock_slowpath(struct qrwlock *lock)
{
+ int cnts;
+
/* Put the writer into the wait queue */
arch_spin_lock(&lock->wait_lock);
@@ -73,9 +75,8 @@ void queued_write_lock_slowpath(struct qrwlock *lock)
/* When no more readers or writers, set the locked flag */
do {
- atomic_cond_read_acquire(&lock->cnts, VAL == _QW_WAITING);
- } while (atomic_cmpxchg_relaxed(&lock->cnts, _QW_WAITING,
- _QW_LOCKED) != _QW_WAITING);
+ cnts = atomic_cond_read_relaxed(&lock->cnts, VAL == _QW_WAITING);
+ } while (!atomic_try_cmpxchg_acquire(&lock->cnts, &cnts, _QW_LOCKED));
unlock:
arch_spin_unlock(&lock->wait_lock);
}