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Message-Id: <1389042806-23967-1-git-send-email-kmo@daterainc.com> Date: Mon, 6 Jan 2014 13:13:26 -0800 From: Kent Overstreet <kmo@...erainc.com> To: tj@...nel.org Cc: linux-kernel@...r.kernel.org, Kent Overstreet <kmo@...erainc.com> Subject: [PATCH] percpu-refcount: Add a WARN() for ref going negative 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. Signed-off-by: Kent Overstreet <kmo@...erainc.com> Cc: Tejun Heo <tj@...nel.org> --- lib/percpu-refcount.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 1a53d497a8..32538f12f8 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -120,6 +120,9 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) atomic_add((int) count - PCPU_COUNT_BIAS, &ref->count); + WARN(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); -- 1.8.5.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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