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percpu-refcount: Add a WARN() for ref going negative

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AIO had a missing get, which led to an ioctx leak - after percpu_ref_kill() the
ref was 0 so percpu_ref_put() never saw it hit 0.

This wasn't noticed at the time because it all happened completely silently,
this adds a WARN() which would've caught the aio bug.

tj: Used WARN_ONCE() instead of WARN().

Signed-off-by: Kent Overstreet <kmo@daterainc.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Kent Overstreet 2014-01-06 13:13:26 -08:00 committed by Tejun Heo
parent 6ce4eac1f6
commit 687b0ad275
1 changed files with 3 additions and 0 deletions
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lib/percpu-refcount.c
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@ -120,6 +120,9 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu)
atomic_add((int) count - PCPU_COUNT_BIAS, &ref->count);
WARN_ONCE(atomic_read(&ref->count) <= 0, "percpu ref <= 0 (%i)",
atomic_read(&ref->count));
/* @ref is viewed as dead on all CPUs, send out kill confirmation */
if (ref->confirm_kill)
ref->confirm_kill(ref);