From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752148AbbASJnC (ORCPT ); Mon, 19 Jan 2015 04:43:02 -0500 Received: from ip4-83-240-67-251.cust.nbox.cz ([83.240.67.251]:39212 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751914AbbASJm6 (ORCPT ); Mon, 19 Jan 2015 04:42:58 -0500 From: Jiri Slaby To: tiwai@suse.de Cc: linux-kernel@vger.kernel.org, Jiri Slaby , Jaroslav Kysela , alsa-devel@alsa-project.org Subject: [PATCH 3/3] sound: dummy, avoid races with timer Date: Mon, 19 Jan 2015 10:42:56 +0100 Message-Id: <1421660576-8435-3-git-send-email-jslaby@suse.cz> X-Mailer: git-send-email 2.2.1 In-Reply-To: <1421660576-8435-1-git-send-email-jslaby@suse.cz> References: <1421660576-8435-1-git-send-email-jslaby@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There is a race between timer and process contexts. Process context does not disable irqs, so when a timer ticks inside process' critical section, the system can deadlock. Fix this by a traditional _irqsave variant of spin_lock. Signed-off-by: Jiri Slaby Cc: Jaroslav Kysela Cc: Takashi Iwai Cc: alsa-devel@alsa-project.org --- sound/drivers/dummy.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c index 6d6bf4093583..18a7cfc99078 100644 --- a/sound/drivers/dummy.c +++ b/sound/drivers/dummy.c @@ -271,10 +271,13 @@ static void dummy_systimer_update(struct dummy_systimer_pcm *dpcm) static int dummy_systimer_start(struct snd_pcm_substream *substream) { struct dummy_systimer_pcm *dpcm = substream->runtime->private_data; - spin_lock(&dpcm->lock); + unsigned long flags; + + spin_lock_irqsave(&dpcm->lock, flags); dpcm->base_time = jiffies; dummy_systimer_rearm(dpcm); - spin_unlock(&dpcm->lock); + spin_unlock_irqrestore(&dpcm->lock, flags); + return 0; } @@ -322,12 +325,14 @@ static snd_pcm_uframes_t dummy_systimer_pointer(struct snd_pcm_substream *substream) { struct dummy_systimer_pcm *dpcm = substream->runtime->private_data; + unsigned long flags; snd_pcm_uframes_t pos; - spin_lock(&dpcm->lock); + spin_lock_irqsave(&dpcm->lock, flags); dummy_systimer_update(dpcm); pos = dpcm->frac_pos / HZ; - spin_unlock(&dpcm->lock); + spin_unlock_irqrestore(&dpcm->lock, flags); + return pos; } -- 2.2.1