From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A039C43334 for ; Mon, 13 Jun 2022 11:01:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350155AbiFMLBm (ORCPT ); Mon, 13 Jun 2022 07:01:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44246 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350280AbiFMKys (ORCPT ); Mon, 13 Jun 2022 06:54:48 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D3C8E13F6C; Mon, 13 Jun 2022 03:30:43 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 6D87C60FCE; Mon, 13 Jun 2022 10:30:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76E2AC341C8; Mon, 13 Jun 2022 10:30:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655116242; bh=xap97sa4M+AXe1p1mmYFq2dbHFYCbMlJWkn8Vt+k8nA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LVlrPozfPzNKCfsoyt8x8/8rYOGeqbEDvg4cSoz+TbhoVWdCGQZRIKpnhs+O/wFVF 9VmhUJsb014iDLoGJcvui6n4tencXY9Oi0lJaC1l+32vdsLQu3dXe19KxC8TbPy0a8 WVanVFUt14f8uoz4JLRMvfVu7uUtxF1MuOqJpwEA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Leo Yan , Mathieu Poirier , Mike Leach , Suzuki K Poulose , "Guilherme G. Piccoli" , Sasha Levin Subject: [PATCH 4.14 148/218] coresight: cpu-debug: Replace mutex with mutex_trylock on panic notifier Date: Mon, 13 Jun 2022 12:10:06 +0200 Message-Id: <20220613094925.079027842@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094908.257446132@linuxfoundation.org> References: <20220613094908.257446132@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Guilherme G. Piccoli [ Upstream commit 1adff542d67a2ed1120955cb219bfff8a9c53f59 ] The panic notifier infrastructure executes registered callbacks when a panic event happens - such callbacks are executed in atomic context, with interrupts and preemption disabled in the running CPU and all other CPUs disabled. That said, mutexes in such context are not a good idea. This patch replaces a regular mutex with a mutex_trylock safer approach; given the nature of the mutex used in the driver, it should be pretty uncommon being unable to acquire such mutex in the panic path, hence no functional change should be observed (and if it is, that would be likely a deadlock with the regular mutex). Fixes: 2227b7c74634 ("coresight: add support for CPU debug module") Cc: Leo Yan Cc: Mathieu Poirier Cc: Mike Leach Cc: Suzuki K Poulose Signed-off-by: Guilherme G. Piccoli Reviewed-by: Suzuki K Poulose Signed-off-by: Suzuki K Poulose Link: https://lore.kernel.org/r/20220427224924.592546-10-gpiccoli@igalia.com Signed-off-by: Sasha Levin --- drivers/hwtracing/coresight/coresight-cpu-debug.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-cpu-debug.c b/drivers/hwtracing/coresight/coresight-cpu-debug.c index 2f6f46ea68e9..ccd59ba26609 100644 --- a/drivers/hwtracing/coresight/coresight-cpu-debug.c +++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c @@ -391,9 +391,10 @@ static int debug_notifier_call(struct notifier_block *self, int cpu; struct debug_drvdata *drvdata; - mutex_lock(&debug_lock); + /* Bail out if we can't acquire the mutex or the functionality is off */ + if (!mutex_trylock(&debug_lock)) + return NOTIFY_DONE; - /* Bail out if the functionality is disabled */ if (!debug_enable) goto skip_dump; @@ -412,7 +413,7 @@ static int debug_notifier_call(struct notifier_block *self, skip_dump: mutex_unlock(&debug_lock); - return 0; + return NOTIFY_DONE; } static struct notifier_block debug_notifier = { -- 2.35.1