From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx2.suse.de ([195.135.220.15]:46598 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752618AbeENM00 (ORCPT ); Mon, 14 May 2018 08:26:26 -0400 Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id B4A49ABE9 for ; Mon, 14 May 2018 12:26:25 +0000 (UTC) From: David Sterba To: linux-btrfs@vger.kernel.org Cc: David Sterba Subject: [PATCH v3 1/3] btrfs: introduce conditional wakeup helpers Date: Mon, 14 May 2018 14:23:46 +0200 Message-Id: In-Reply-To: References: Sender: linux-btrfs-owner@vger.kernel.org List-ID: Add convenience wrappers for the waitqueue management that involves memory barriers to prevent deadlocks. The helpers will let us remove barriers and the necessary comments in several places. Reviewed-by: Nikolay Borisov Signed-off-by: David Sterba --- fs/btrfs/ctree.h | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 2771cc56a622..1389942f3be1 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -3765,4 +3765,26 @@ static inline int btrfs_is_testing(struct btrfs_fs_info *fs_info) return 0; } +static inline void cond_wake_up(struct wait_queue_head *wq) +{ + /* + * This implies a full smp_mb barrier, see comments for + * waitqueue_active why. + */ + if (wq_has_sleeper(wq)) + wake_up(wq); +} + +static inline void cond_wake_up_nomb(struct wait_queue_head *wq) +{ + /* + * Special case for conditional wakeup where the barrier required for + * waitqueue_active is implied by some of the preceding code. Eg. one + * of such atomic operations (atomic_dec_and_return, ...), or a + * unlock/lock sequence, etc. + */ + if (waitqueue_active(wq)) + wake_up(wq); +} + #endif -- 2.16.2