Messages in this thread Patch in this message | | | Date | Tue, 22 Sep 2009 13:34:16 GMT | From | tip-bot for Ingo Molnar <> | Subject | [tip:core/printk] ratelimit: Fix/allow use in atomic contexts |
| |
Commit-ID: edaac8e3167501cda336231d00611bf59c164346 Gitweb: http://git.kernel.org/tip/edaac8e3167501cda336231d00611bf59c164346 Author: Ingo Molnar <mingo@elte.hu> AuthorDate: Tue, 22 Sep 2009 14:44:11 +0200 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Tue, 22 Sep 2009 14:05:48 +0200
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 <a.p.zijlstra@chello.nl> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: David S. Miller <davem@davemloft.net> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- lib/ratelimit.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/lib/ratelimit.c b/lib/ratelimit.c index 0e2c28e..69bfcac 100644 --- a/lib/ratelimit.c +++ b/lib/ratelimit.c @@ -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;
| |