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jump_label: Add RELEASE barrier after text changes 

In the unlikely case text modification does not fully order things,
add some extra ordering of our own to ensure we only enabled the fast
path after all text is visible.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2017-08-01 23:58:50 +02:00 committed by Ingo Molnar
parent be040bea90
commit d0646a6f55
1 changed files with 9 additions and 2 deletions
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11
kernel/jump_label.c
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@ -108,7 +108,11 @@ void static_key_slow_inc(struct static_key *key)
if (atomic_read(&key->enabled) == 0) { if (atomic_read(&key->enabled) == 0) {
atomic_set(&key->enabled, -1); atomic_set(&key->enabled, -1);
jump_label_update(key); jump_label_update(key);
atomic_set(&key->enabled, 1); /*
* Ensure that if the above cmpxchg loop observes our positive
* value, it must also observe all the text changes.
*/
atomic_set_release(&key->enabled, 1);
} else { } else {
atomic_inc(&key->enabled); atomic_inc(&key->enabled);
} }
@ -130,7 +134,10 @@ void static_key_enable(struct static_key *key)
if (atomic_read(&key->enabled) == 0) { if (atomic_read(&key->enabled) == 0) {
atomic_set(&key->enabled, -1); atomic_set(&key->enabled, -1);
jump_label_update(key); jump_label_update(key);
atomic_set(&key->enabled, 1); /*
* See static_key_slow_inc().
*/
atomic_set_release(&key->enabled, 1);
} }
jump_label_unlock(); jump_label_unlock();
cpus_read_unlock(); cpus_read_unlock();