From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932088AbbFQW5R (ORCPT ); Wed, 17 Jun 2015 18:57:17 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:35517 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751225AbbFQW3t (ORCPT ); Wed, 17 Jun 2015 18:29:49 -0400 From: Kamal Mostafa To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Takashi Iwai , Kamal Mostafa Subject: [PATCH 3.13.y-ckt 021/122] ALSA: emux: Fix mutex deadlock at unloading Date: Wed, 17 Jun 2015 15:27:28 -0700 Message-Id: <1434580149-3095-22-git-send-email-kamal@canonical.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1434580149-3095-1-git-send-email-kamal@canonical.com> References: <1434580149-3095-1-git-send-email-kamal@canonical.com> X-Extended-Stable: 3.13 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.13.11-ckt22 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Takashi Iwai 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: Kamal Mostafa --- 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