6.10-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
[ Upstream commit 9bc2ff871f00437ad2f10c1eceff51aaa72b478f ]
Make the code more obvious and add proper comments to avoid future head scratching.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lkml.kernel.org/r/20240610124406.548322963@linutronix.de Stable-dep-of: 1d7f856c2ca4 ("jump_label: Fix static_key_slow_dec() yet again") Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/jump_label.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/kernel/jump_label.c b/kernel/jump_label.c index c6ac0d0377d72..781a1298ce2c2 100644 --- a/kernel/jump_label.c +++ b/kernel/jump_label.c @@ -159,22 +159,24 @@ bool static_key_slow_inc_cpuslocked(struct static_key *key) if (static_key_fast_inc_not_disabled(key)) return true;
- jump_label_lock(); - if (atomic_read(&key->enabled) == 0) { - atomic_set(&key->enabled, -1); + guard(mutex)(&jump_label_mutex); + /* Try to mark it as 'enabling in progress. */ + if (!atomic_cmpxchg(&key->enabled, 0, -1)) { jump_label_update(key); /* - * Ensure that if the above cmpxchg loop observes our positive - * value, it must also observe all the text changes. + * Ensure that when static_key_fast_inc_not_disabled() or + * static_key_slow_try_dec() observe the positive value, + * they must also observe all the text changes. */ atomic_set_release(&key->enabled, 1); } else { - if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key))) { - jump_label_unlock(); + /* + * While holding the mutex this should never observe + * anything else than a value >= 1 and succeed + */ + if (WARN_ON_ONCE(!static_key_fast_inc_not_disabled(key))) return false; - } } - jump_label_unlock(); return true; }