From patchwork Tue Jan 22 16:19:14 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Takashi Iwai X-Patchwork-Id: 10775859 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1FF60139A for ; Tue, 22 Jan 2019 16:20:02 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 09F982833E for ; Tue, 22 Jan 2019 16:20:02 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id EE2252B164; Tue, 22 Jan 2019 16:20:01 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 374CD2833E for ; Tue, 22 Jan 2019 16:20:01 +0000 (UTC) Received: from alsa0.perex.cz (localhost [127.0.0.1]) by alsa0.perex.cz (Postfix) with ESMTP id A90832674F7; Tue, 22 Jan 2019 17:19:31 +0100 (CET) X-Original-To: alsa-devel@alsa-project.org Delivered-To: alsa-devel@alsa-project.org Received: by alsa0.perex.cz (Postfix, from userid 1000) id 491862674B9; Tue, 22 Jan 2019 17:19:24 +0100 (CET) Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by alsa0.perex.cz (Postfix) with ESMTP id 4B7DD2674C6 for ; Tue, 22 Jan 2019 17:19:20 +0100 (CET) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 99297B082 for ; Tue, 22 Jan 2019 16:19:18 +0000 (UTC) From: Takashi Iwai To: alsa-devel@alsa-project.org Date: Tue, 22 Jan 2019 17:19:14 +0100 Message-Id: <20190122161915.8445-7-tiwai@suse.de> X-Mailer: git-send-email 2.16.4 In-Reply-To: <20190122161915.8445-1-tiwai@suse.de> References: <20190122161915.8445-1-tiwai@suse.de> Subject: [alsa-devel] [PATCH 6/7] ALSA: pcm: Remove down_write() hack for snd_pcm_link_rwsem X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org X-Virus-Scanned: ClamAV using ClamSMTP Remove the hackish down_write_nonfifo() that was introduced as a workaround of rwsem deadlock. It used to be a problem for non-atomic PCM streams that take the rwsem for the locking and hit the high lock contention. Since the current PCM locking refactoring, we'll no longer hit it as the hot code-paths don't take global locks. Signed-off-by: Takashi Iwai --- sound/core/pcm_native.c | 16 ++-------------- 1 file changed, 2 insertions(+), 14 deletions(-) diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c index cbde23fc67a9..f450083eb073 100644 --- a/sound/core/pcm_native.c +++ b/sound/core/pcm_native.c @@ -87,18 +87,6 @@ static int snd_pcm_open(struct file *file, struct snd_pcm *pcm, int stream); static DECLARE_RWSEM(snd_pcm_link_rwsem); -/* Writer in rwsem may block readers even during its waiting in queue, - * and this may lead to a deadlock when the code path takes read sem - * twice (e.g. one in snd_pcm_action_nonatomic() and another in - * snd_pcm_stream_lock()). As a (suboptimal) workaround, let writer to - * sleep until all the readers are completed without blocking by writer. - */ -static inline void down_write_nonfifo(struct rw_semaphore *lock) -{ - while (!down_write_trylock(lock)) - msleep(1); -} - void snd_pcm_group_init(struct snd_pcm_group *group) { spin_lock_init(&group->lock); @@ -2052,7 +2040,7 @@ static int snd_pcm_link(struct snd_pcm_substream *substream, int fd) } snd_pcm_group_init(group); - down_write_nonfifo(&snd_pcm_link_rwsem); + down_write(&snd_pcm_link_rwsem); if (substream->runtime->status->state == SNDRV_PCM_STATE_OPEN || substream->runtime->status->state != substream1->runtime->status->state || substream->pcm->nonatomic != substream1->pcm->nonatomic) { @@ -2100,7 +2088,7 @@ static int snd_pcm_unlink(struct snd_pcm_substream *substream) bool do_free = false; int res = 0; - down_write_nonfifo(&snd_pcm_link_rwsem); + down_write(&snd_pcm_link_rwsem); if (!snd_pcm_stream_linked(substream)) { res = -EALREADY;