Commit-ID: edaac8e3167501cda336231d00611bf59c164346 Gitweb: http://git.kernel.org/tip/edaac8e3167501cda336231d00611bf59c164346 Author: Ingo Molnar <mingo@xxxxxxx> AuthorDate: Tue, 22 Sep 2009 14:44:11 +0200 Committer: Ingo Molnar <mingo@xxxxxxx> 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@xxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: David S. Miller <davem@xxxxxxxxxxxxx> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- 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; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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