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lockdep: Fix redundant_hardirqs_on incremented with irqs enabled

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When a path restore the flags while irqs are already enabled, we
update the per cpu var redundant_hardirqs_on in a racy fashion
and debug_atomic_inc() warns about this situation.

In this particular case, loosing a few hits in a stat is not a big
deal, so increment it without protection.

v2: Don't bother with disabling irq, we can miss one count in
    rare situations

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: David Miller <davem@davemloft.net>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Frederic Weisbecker 2010-04-15 23:10:42 +02:00
parent 868c522b1b
commit 8795d7717c
1 changed files with 6 additions and 1 deletions
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7
kernel/lockdep.c
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@ -2298,7 +2298,12 @@ void trace_hardirqs_on_caller(unsigned long ip)
return;
if (unlikely(curr->hardirqs_enabled)) {
debug_atomic_inc(redundant_hardirqs_on);
/*
* Neither irq nor preemption are disabled here
* so this is racy by nature but loosing one hit
* in a stat is not a big deal.
*/
this_cpu_inc(lockdep_stats.redundant_hardirqs_on);
return;
}
/* we'll do an OFF -> ON transition: */