6.1-stable review patch. If anyone has any objections, please let me know.
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From: Peter Zijlstra peterz@infradead.org
[ Upstream commit 224fa3552029a3d14bec7acf72ded8171d551b88 ]
Per the example of:
!atomic_cmpxchg(&key->enabled, 0, 1)
the inverse was written as:
atomic_cmpxchg(&key->enabled, 1, 0)
except of course, that while !old is only true for old == 0, old is true for everything except old == 0.
Fix it to read:
atomic_cmpxchg(&key->enabled, 1, 0) == 1
such that only the 1->0 transition returns true and goes on to disable the keys.
Fixes: 83ab38ef0a0b ("jump_label: Fix concurrency issues in static_key_slow_dec()") Reported-by: Darrick J. Wong djwong@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Tested-by: Darrick J. Wong djwong@kernel.org Link: https://lkml.kernel.org/r/20240731105557.GY33588@noisy.programming.kicks-ass... Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/jump_label.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/jump_label.c b/kernel/jump_label.c index eec802175ccc6..1ed269b2c4035 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -231,7 +231,7 @@ void static_key_disable_cpuslocked(struct static_key *key) }
jump_label_lock(); - if (atomic_cmpxchg(&key->enabled, 1, 0)) + if (atomic_cmpxchg(&key->enabled, 1, 0) == 1) jump_label_update(key); jump_label_unlock(); } @@ -284,7 +284,7 @@ static void __static_key_slow_dec_cpuslocked(struct static_key *key) return;
guard(mutex)(&jump_label_mutex); - if (atomic_cmpxchg(&key->enabled, 1, 0)) + if (atomic_cmpxchg(&key->enabled, 1, 0) == 1) jump_label_update(key); else WARN_ON_ONCE(!static_key_slow_try_dec(key));