Messages in this thread Patch in this message | | | From | Kent Overstreet <> | Subject | [PATCH] percpu-refcount: Don't use silly cmpxchg() | Date | Mon, 3 Jun 2013 16:02:29 -0700 |
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The cmpxcgh() was just to ensure the debug check didn't race, which was a bit excessive. The caller is supposed to do the appropriate synchronization, which means percpu_ref_kill() can just do a simple store.
Signed-off-by: Kent Overstreet <koverstreet@google.com> --- lib/percpu-refcount.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-)
diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index e65820a..04be7ea 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -107,22 +107,11 @@ static void percpu_ref_kill_rcu(struct rcu_head *rcu) */ void percpu_ref_kill(struct percpu_ref *ref) { - unsigned __percpu *pcpu_count, *old, *new; + WARN_ONCE(REF_STATUS(ref->pcpu_count) == PCPU_REF_DEAD, + "percpu_ref_kill() called more than once!\n"); - pcpu_count = ACCESS_ONCE(ref->pcpu_count); - - do { - if (REF_STATUS(pcpu_count) == PCPU_REF_DEAD) { - WARN(1, "percpu_ref_kill() called more than once!\n"); - return; - } - - old = pcpu_count; - new = (unsigned __percpu *) - (((unsigned long) pcpu_count)|PCPU_REF_DEAD); - - pcpu_count = cmpxchg(&ref->pcpu_count, old, new); - } while (pcpu_count != old); + ref->pcpu_count = (unsigned __percpu *) + (((unsigned long) ref->pcpu_count)|PCPU_REF_DEAD); call_rcu(&ref->rcu, percpu_ref_kill_rcu); } -- 1.8.2.1
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