From 687b0ad2751ca8ea418396fa780e22571fba76a8 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Mon, 6 Jan 2014 13:13:26 -0800 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. tj: Used WARN_ONCE() instead of WARN(). Signed-off-by: Kent Overstreet Signed-off-by: Tejun Heo --- lib/percpu-refcount.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 1a53d497a8c5..963b7034a51b 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_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); -- 2.20.1