path: root/lib
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authorIngo Molnar <mingo@elte.hu>2009-09-22 14:44:11 +0200
committerIngo Molnar <mingo@elte.hu>2009-09-22 14:05:48 +0200
commitedaac8e3167501cda336231d00611bf59c164346 (patch)
tree5ebf22336dccef4fcd601e0a6a2d13ea347ec568 /lib
parent979f693def9084a452846365dfde5dcb28366333 (diff)
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')
1 files changed, 9 insertions, 1 deletions
diff --git a/lib/ratelimit.c b/lib/ratelimit.c
index 0e2c28e8a0c..69bfcacda16 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;