From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754005AbbIOJIj (ORCPT ); Tue, 15 Sep 2015 05:08:39 -0400 Received: from mail.kernel.org ([198.145.29.136]:52267 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752955AbbIOJIh (ORCPT ); Tue, 15 Sep 2015 05:08:37 -0400 From: lizf@kernel.org To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Takashi Iwai , Zefan Li Subject: [PATCH 3.4 058/146] ALSA: emux: Fix mutex deadlock at unloading Date: Tue, 15 Sep 2015 17:02:53 +0800 Message-Id: <1442307861-32031-58-git-send-email-lizf@kernel.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1442307787-31952-1-git-send-email-lizf@kernel.org> References: <1442307787-31952-1-git-send-email-lizf@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Takashi Iwai 3.4.109-rc1 review patch. If anyone has any objections, please let me know. ------------------ commit 07b0e5d49d227e3950cb13a3e8caf248ef2a310e upstream. The emux-synth driver has a possible AB/BA mutex deadlock at unloading the emu10k1 driver: snd_emux_free() -> snd_emux_detach_seq(): mutex_lock(&emu->register_mutex) -> snd_seq_delete_kernel_client() -> snd_seq_free_client(): mutex_lock(®ister_mutex) snd_seq_release() -> snd_seq_free_client(): mutex_lock(®ister_mutex) -> snd_seq_delete_all_ports() -> snd_emux_unuse(): mutex_lock(&emu->register_mutex) Basically snd_emux_detach_seq() doesn't need a protection of emu->register_mutex as it's already being unregistered. So, we can get rid of this for avoiding the deadlock. Signed-off-by: Takashi Iwai Signed-off-by: Zefan Li --- sound/synth/emux/emux_seq.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/sound/synth/emux/emux_seq.c b/sound/synth/emux/emux_seq.c index 7778b8e..188fda0e 100644 --- a/sound/synth/emux/emux_seq.c +++ b/sound/synth/emux/emux_seq.c @@ -124,12 +124,10 @@ snd_emux_detach_seq(struct snd_emux *emu) if (emu->voices) snd_emux_terminate_all(emu); - mutex_lock(&emu->register_mutex); if (emu->client >= 0) { snd_seq_delete_kernel_client(emu->client); emu->client = -1; } - mutex_unlock(&emu->register_mutex); } -- 1.9.1