From edaac8e3167501cda336231d00611bf59c164346 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 22 Sep 2009 14:44:11 +0200 Subject: [PATCH] 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: Signed-off-by: Ingo Molnar --- lib/ratelimit.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) 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; -- 2.20.1