From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752839AbaIHCMw (ORCPT ); Sun, 7 Sep 2014 22:12:52 -0400 Received: from mail-pd0-f172.google.com ([209.85.192.172]:53433 "EHLO mail-pd0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752618AbaIHCMe (ORCPT ); Sun, 7 Sep 2014 22:12:34 -0400 From: Tejun Heo To: cl@linux-foundation.org, kmo@daterainc.com Cc: linux-kernel@vger.kernel.org, Tejun Heo Subject: [PATCH 2/3] percpu-refcount: implement percpu_ref_set_killed() Date: Mon, 8 Sep 2014 11:12:21 +0900 Message-Id: <1410142342-8185-3-git-send-email-tj@kernel.org> X-Mailer: git-send-email 1.9.3 In-Reply-To: <1410142342-8185-1-git-send-email-tj@kernel.org> References: <1410142342-8185-1-git-send-email-tj@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With the recent addition of percpu_ref_reinit(), percpu_ref now can be used as a persistent switch which can be turned on and off repeatedly where turning off maps to killing the ref and waiting for it to drain; however, there currently isn't a way to initialize a percpu_ref in its off (killed and drained) state, which can be inconvenient for certain persistent switch use cases. This patch adds percpu_ref_set_killed() which forces the percpu_ref into its killed and drained state. The caller is responsible for ensuring that no one else is using the ref. This can be used to force the percpu_ref into its off state after initialization. Signed-off-by: Tejun Heo Cc: Kent Overstreet --- include/linux/percpu-refcount.h | 1 + lib/percpu-refcount.c | 14 ++++++++++++++ 2 files changed, 15 insertions(+) diff --git a/include/linux/percpu-refcount.h b/include/linux/percpu-refcount.h index ee83251..97a7d2a 100644 --- 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, gfp_t gfp); void percpu_ref_reinit(struct percpu_ref *ref); +void percpu_ref_set_killed(struct percpu_ref *ref); void percpu_ref_exit(struct percpu_ref *ref); void percpu_ref_kill_and_confirm(struct percpu_ref *ref, percpu_ref_func_t *confirm_kill); diff --git a/lib/percpu-refcount.c b/lib/percpu-refcount.c index 70d28c9..a6768f6 100644 --- a/lib/percpu-refcount.c +++ b/lib/percpu-refcount.c @@ -98,6 +98,20 @@ void percpu_ref_reinit(struct percpu_ref *ref) EXPORT_SYMBOL_GPL(percpu_ref_reinit); /** + * percpu_ref_set_killed - force a percpu refcount to the killed state + * @ref: percpu_ref to set killed for + * + * Set @ref's state to killed. This function doesn't care about the + * current state or in-progress operations on @ref and the caller is + * responsible for ensuring that @ref isn't being used by anyone else. + */ +void percpu_ref_set_killed(struct percpu_ref *ref) +{ + ref->pcpu_count_ptr |= PCPU_REF_DEAD; + atomic_set(&ref->count, 0); +} + +/** * percpu_ref_exit - undo percpu_ref_init() * @ref: percpu_ref to exit * -- 1.9.3