The following commit has been merged into the locking/core branch of tip:
Commit-ID: 9bc2ff871f00437ad2f10c1eceff51aaa72b478f
Gitweb: https://git.kernel.org/tip/9bc2ff871f00437ad2f10c1eceff51aaa72b478f
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Mon, 10 Jun 2024 14:46:39 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 11 Jun 2024 11:25:24 +02:00
jump_label: Simplify and clarify static_key_fast_inc_cpus_locked()
Make the code more obvious and add proper comments to avoid future head
scratching.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20240610124406.548322963@xxxxxxxxxxxxx
---
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 4d06ec2..4ad5ed8 100644
--- a/kernel/jump_label.c
+++ b/kernel/jump_label.c
@@ -162,22 +162,24 @@ 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;
}
|