Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932598Ab3FMDwk (ORCPT ); Wed, 12 Jun 2013 23:52:40 -0400 Received: from mail-yh0-f42.google.com ([209.85.213.42]:49503 "EHLO mail-yh0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932403Ab3FMDwj (ORCPT ); Wed, 12 Jun 2013 23:52:39 -0400 Date: Wed, 12 Jun 2013 20:52:35 -0700 From: Tejun Heo To: Kent Overstreet , linux-kernel@vger.kernel.org, Rusty Russell , Oleg Nesterov , Christoph Lameter Subject: [PATCH percpu/for-3.11 2/2] percpu-refcount: implement percpu_ref_cancel_init() Message-ID: <20130613035235.GE9451@mtj.dyndns.org> References: <20130613035201.GD9451@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130613035201.GD9451@mtj.dyndns.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2607 Lines: 69 Normally, percpu_ref_init() initializes and percpu_ref_kill*() initiates destruction which completes asynchronously. The asynchronous destruction can be problematic in init failure path where the caller wants to destroy half-constructed object - distinguishing half-constructed objects from the usual release method can be painful for complex objects. This patch implements percpu_ref_cancel_init() which synchronously destroys the percpu_ref without invoking release. To avoid unintentional misuses, the function requires the ref to have finished percpu_ref_init() but never used and triggers WARN otherwise. Signed-off-by: Tejun Heo --- include/linux/percpu-refcount.h | 1 + lib/percpu-refcount.c | 27 +++++++++++++++++++++++++++ 2 files changed, 28 insertions(+) --- a/include/linux/percpu-refcount.h +++ b/include/linux/percpu-refcount.h @@ -69,6 +69,7 @@ struct percpu_ref { int __must_check percpu_ref_init(struct percpu_ref *ref, percpu_ref_func_t *release); +void percpu_ref_cancel_init(struct percpu_ref *ref); void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill); --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -54,6 +54,33 @@ int percpu_ref_init(struct percpu_ref *r return 0; } +/** + * percpu_ref_cancel_init - cancel percpu_ref_init() + * @ref: percpu_ref to cancel init for + * + * Once a percpu_ref is initialized, its destruction is initiated by + * percpu_ref_kill*() and completes asynchronously, which can be painful to + * do when destroying a half-constructed object in init failure path. + * + * This function destroys @ref without invoking @ref->release and the + * memory area containing it can be freed immediately on return. To + * prevent accidental misuse, it's required that @ref has finished + * percpu_ref_init(), whether successful or not, but never used. + */ +void percpu_ref_cancel_init(struct percpu_ref *ref) +{ + unsigned __percpu *pcpu_count = ref->pcpu_count; + int cpu; + + WARN_ON_ONCE(atomic_read(&ref->count) != 1 + PCPU_COUNT_BIAS); + + if (pcpu_count) { + for_each_possible_cpu(cpu) + WARN_ON_ONCE(*per_cpu_ptr(pcpu_count, cpu)); + free_percpu(ref->pcpu_count); + } +} + static void percpu_ref_kill_rcu(struct rcu_head *rcu) { struct percpu_ref *ref = container_of(rcu, struct percpu_ref, rcu); -- 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/