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| author | Roman Pen <roman.penyaev@profitbricks.com> | 2016-08-11 19:27:09 +0200 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2016-08-11 13:52:23 -0400 |
| commit | a67823c1ed1092160da94c31e6da5aeb35dca81c (patch) | |
| tree | 7c0a2544991fddf233fc05158b61d2d9bd2927b2 /lib/percpu-refcount.c | |
| parent | 33e465ce7cb30b71c113a26f36d293b545a28e12 (diff) | |
| download | linux-a67823c1ed1092160da94c31e6da5aeb35dca81c.tar.bz2 | |
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>
Diffstat (limited to 'lib/percpu-refcount.c')
| -rw-r--r-- | lib/percpu-refcount.c | 3 |
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; } |