Commit 9bc2ff87 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Peter Zijlstra
Browse files

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: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20240610124406.548322963@linutronix.de
parent 695ef796

kernel/jump_label.c

+11 −9
Original line number Diff line number Diff line
@@ -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;

}