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authorRoman Pen <roman.penyaev@profitbricks.com>2016-08-11 19:27:09 +0200
committerTejun Heo <tj@kernel.org>2016-08-11 13:52:23 -0400
commita67823c1ed1092160da94c31e6da5aeb35dca81c (patch)
tree7c0a2544991fddf233fc05158b61d2d9bd2927b2
parent33e465ce7cb30b71c113a26f36d293b545a28e12 (diff)
percpu-refcount: init ->confirm_switch member properly
This patch targets two things which are related to ->confirm_switch: 1. Init ->confirm_switch pointer with NULL on percpu_ref_init() or kernel frightfully complains with WARN_ON_ONCE(ref->confirm_switch) at __percpu_ref_switch_to_atomic if memory chunk was not properly zeroed. 2. Warn if RCU callback is still in progress on percpu_ref_exit(). The race still exists, because percpu_ref_call_confirm_rcu() drops ->confirm_switch to NULL early, but that is only a warning and still the caller is responsible that ref is no longer in active use. Hopefully that can help to catch incorrect usage of percpu-refcount. Signed-off-by: Roman Pen <roman.penyaev@profitbricks.com> Cc: Tejun Heo <tj@kernel.org> Cc: linux-kernel@vger.kernel.org Signed-off-by: Tejun Heo <tj@kernel.org>
-rw-r--r--lib/percpu-refcount.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c
index c69938e4b0d5..9ac959ef4cae 100644
--- a/lib/percpu-refcount.c
+++ b/lib/percpu-refcount.c
@@ -83,6 +83,7 @@ int percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release,
atomic_long_set(&ref->count, start_count);
ref->release = release;
+ ref->confirm_switch = NULL;
return 0;
}
EXPORT_SYMBOL_GPL(percpu_ref_init);
@@ -102,6 +103,8 @@ void percpu_ref_exit(struct percpu_ref *ref)
unsigned long __percpu *percpu_count = percpu_count_ptr(ref);
if (percpu_count) {
+ /* non-NULL confirm_switch indicates switching in progress */
+ WARN_ON_ONCE(ref->confirm_switch);
free_percpu(percpu_count);
ref->percpu_count_ptr = __PERCPU_REF_ATOMIC_DEAD;
}