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| author | Ingo Molnar <mingo@elte.hu> | 2009-09-22 14:44:11 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-09-22 14:05:48 +0200 |
| commit | edaac8e3167501cda336231d00611bf59c164346 (patch) | |
| tree | 5ebf22336dccef4fcd601e0a6a2d13ea347ec568 /lib/ratelimit.c | |
| parent | 979f693def9084a452846365dfde5dcb28366333 (diff) | |
| download | lwn-edaac8e3167501cda336231d00611bf59c164346.tar.gz lwn-edaac8e3167501cda336231d00611bf59c164346.zip | |
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>
Diffstat (limited to 'lib/ratelimit.c')
| -rw-r--r-- | lib/ratelimit.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/lib/ratelimit.c b/lib/ratelimit.c index 0e2c28e8a0ca..69bfcacda16d 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; |