From patchwork Tue Jun 11 02:39:28 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Guoqing Jiang X-Patchwork-Id: 1946041 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@legolas.ozlabs.org Authentication-Results: legolas.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=lists.ubuntu.com (client-ip=185.125.189.65; helo=lists.ubuntu.com; envelope-from=kernel-team-bounces@lists.ubuntu.com; receiver=patchwork.ozlabs.org) Received: from lists.ubuntu.com (lists.ubuntu.com [185.125.189.65]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by legolas.ozlabs.org (Postfix) with ESMTPS id 4VytHg6wyzz20Tk for ; Tue, 11 Jun 2024 12:42:23 +1000 (AEST) Received: from localhost ([127.0.0.1] helo=lists.ubuntu.com) by lists.ubuntu.com with esmtp (Exim 4.86_2) (envelope-from ) id 1sGrSi-0005c5-24; Tue, 11 Jun 2024 02:42:16 +0000 Received: from smtp-relay-canonical-0.internal ([10.131.114.83] helo=smtp-relay-canonical-0.canonical.com) by lists.ubuntu.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1sGrSg-0005aq-0y for kernel-team@lists.ubuntu.com; Tue, 11 Jun 2024 02:42:14 +0000 Received: from localhost.localdomain (1.general.gjiang.uk.vpn [10.172.198.26]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by smtp-relay-canonical-0.canonical.com (Postfix) with ESMTPSA id 2736E40FAE for ; Tue, 11 Jun 2024 02:42:11 +0000 (UTC) From: Guoqing Jiang To: kernel-team@lists.ubuntu.com Subject: [SRU][M][PATCH V2] ALSA: Fix deadlocks with kctl removals at disconnection Date: Tue, 11 Jun 2024 10:39:28 +0800 Message-Id: <20240611023928.23915-4-guoqing.jiang@canonical.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240611023928.23915-1-guoqing.jiang@canonical.com> References: <20240611023928.23915-1-guoqing.jiang@canonical.com> MIME-Version: 1.0 X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.20 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: "kernel-team" From: Takashi Iwai BugLink: https://bugs.launchpad.net/bugs/2061091 In snd_card_disconnect(), we set card->shutdown flag at the beginning, call callbacks and do sync for card->power_ref_sleep waiters at the end. The callback may delete a kctl element, and this can lead to a deadlock when the device was in the suspended state. Namely: * A process waits for the power up at snd_power_ref_and_wait() in snd_ctl_info() or read/write() inside card->controls_rwsem. * The system gets disconnected meanwhile, and the driver tries to delete a kctl via snd_ctl_remove*(); it tries to take card->controls_rwsem again, but this is already locked by the above. Since the sleeper isn't woken up, this deadlocks. An easy fix is to wake up sleepers before processing the driver disconnect callbacks but right after setting the card->shutdown flag. Then all sleepers will abort immediately, and the code flows again. So, basically this patch moves the wait_event() call at the right timing. While we're at it, just to be sure, call wait_event_all() instead of wait_event(), although we don't use exclusive events on this queue for now. Link: https://bugzilla.kernel.org/show_bug.cgi?id=218816 Cc: Reviewed-by: Jaroslav Kysela Link: https://lore.kernel.org/r/20240510101424.6279-1-tiwai@suse.de Signed-off-by: Takashi Iwai (cherry picked from commit 87988a534d8e12f2e6fc01fe63e6c1925dc5307c) Signed-off-by: Guoqing Jiang --- sound/core/init.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/sound/core/init.c b/sound/core/init.c index baef2688d0cf..21880fc95d89 100644 --- a/sound/core/init.c +++ b/sound/core/init.c @@ -518,6 +518,14 @@ void snd_card_disconnect(struct snd_card *card) } spin_unlock(&card->files_lock); +#ifdef CONFIG_PM + /* wake up sleepers here before other callbacks for avoiding potential + * deadlocks with other locks (e.g. in kctls); + * then this notifies the shutdown and sleepers would abort immediately + */ + wake_up_all(&card->power_sleep); +#endif + /* notify all connected devices about disconnection */ /* at this point, they cannot respond to any calls except release() */ @@ -545,7 +553,6 @@ void snd_card_disconnect(struct snd_card *card) mutex_unlock(&snd_card_mutex); #ifdef CONFIG_PM - wake_up(&card->power_sleep); snd_power_sync_ref(card); #endif }