Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759241Ab3FCXCp (ORCPT ); Mon, 3 Jun 2013 19:02:45 -0400 Received: from mail-pd0-f181.google.com ([209.85.192.181]:44373 "EHLO mail-pd0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758645Ab3FCXCj (ORCPT ); Mon, 3 Jun 2013 19:02:39 -0400 From: Kent Overstreet To: tj@kernel.org Cc: linux-kernel@vger.kernel.org, Kent Overstreet Subject: [PATCH] percpu-refcount: Don't use silly cmpxchg() Date: Mon, 3 Jun 2013 16:02:29 -0700 Message-Id: <1370300549-2177-1-git-send-email-koverstreet@google.com> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1370039205-14071-1-git-send-email-koverstreet@google.com> References: <1370039205-14071-1-git-send-email-koverstreet@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1574 Lines: 49 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 --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/