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 7B42DC43334 for ; Mon, 13 Jun 2022 12:32:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1352246AbiFMMcZ (ORCPT ); Mon, 13 Jun 2022 08:32:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41878 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357799AbiFMM32 (ORCPT ); Mon, 13 Jun 2022 08:29:28 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E5DA5A161; Mon, 13 Jun 2022 04:06:34 -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 6C2F0614DC; Mon, 13 Jun 2022 11:06:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76A53C34114; Mon, 13 Jun 2022 11:06:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1655118377; bh=c2tgN3p+zjBZ0UI8I3rzEyvmKixlS5QbGliVZrXxf60=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aAtHU7n6vCVOVGYCj29+QkYm/zMjLqvULxGhKwhHJ9eMPDyxP/+fDvdNZCtEwe2SL KUsSE44faOCOt5QVKF4gbON/N2Dp0K1xI0oBj2gWBLnbqQy1mpNgek6FFmBrgkT8R2 /TY+qxvlLaM0O2QXTHoTQl8HbXtdVyoBdLUlCAVA= 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 5.10 027/172] coresight: cpu-debug: Replace mutex with mutex_trylock on panic notifier Date: Mon, 13 Jun 2022 12:09:47 +0200 Message-Id: <20220613094856.943105489@linuxfoundation.org> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220613094850.166931805@linuxfoundation.org> References: <20220613094850.166931805@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 2dcf13de751f..1e98562f4287 100644 --- a/drivers/hwtracing/coresight/coresight-cpu-debug.c +++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c @@ -379,9 +379,10 @@ 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; @@ -400,7 +401,7 @@ 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