Commit edaac8e3 authored by Ingo Molnar's avatar Ingo Molnar

ratelimit: Fix/allow use in atomic contexts

I'd like to use printk_ratelimit() in NMI context, but it's not
robust right now due to spinlock usage in lib/ratelimit.c. If an
NMI is unlucky enough to hit just that spot we might lock up trying
to take the spinlock again.

Fix that by using a trylock variant. If we contend on that lock we
can genuinely skip the message because the state is just being
accessed by another CPU (or by this CPU).

( We could use atomics for the suppressed messages field, but
  i doubt it matters in practice and it makes the code heavier. )

Cc: Peter Zijlstra <>
Cc: Andrew Morton <>
Cc: Linus Torvalds <>
Cc: David S. Miller <>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <>
parent 979f693d
......@@ -28,7 +28,15 @@ int __ratelimit(struct ratelimit_state *rs)
if (!rs->interval)
return 1;
spin_lock_irqsave(&rs->lock, flags);
* If we contend on this state's lock then almost
* by definition we are too busy to print a message,
* in addition to the one that will be printed by
* the entity that is holding the lock already:
if (!spin_trylock_irqsave(&rs->lock, flags))
return 1;
if (!rs->begin)
rs->begin = jiffies;
Markdown is supported
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment