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 X-Spam-Level: X-Spam-Status: No, score=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9B41C2D0C6 for ; Fri, 27 Dec 2019 17:44:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 872B121582 for ; Fri, 27 Dec 2019 17:44:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1577468642; bh=Emq/9B2AkW4YhJSNYylruI7SPFCFSURyWY2lX/sSuec=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=zqhyElxca80K47FcCmu5Bcz+fkpos0owCJbEMjaEQTXXWj0NpTdkB+ZqZuOW4Vmj/ 10BA2esMQV6Kn593AF5S/XP6+qTDvabm+2+5vTIoxq2hZtC2hkF4Ow2PcgvN0i/Mk+ 0e2qLrDUtyCWYQ6E20x6m+f5WuEpmR1hP7JxwWk0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728320AbfL0RoB (ORCPT ); Fri, 27 Dec 2019 12:44:01 -0500 Received: from mail.kernel.org ([198.145.29.99]:41766 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728308AbfL0Rn5 (ORCPT ); Fri, 27 Dec 2019 12:43:57 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ACA462464E; Fri, 27 Dec 2019 17:43:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1577468637; bh=Emq/9B2AkW4YhJSNYylruI7SPFCFSURyWY2lX/sSuec=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zy1yK41vXYWF4K5X93xG1fkaP1iJA1UHm46ixboqebgLOpW2/Wvk9kve5J6Ky4+JW zcCQLZUd/bGnxygplHny/SB63EMB7wTONYF67yRf+7QRsY2MGDSvdcXCnBlZNGGj/1 1hyv0Jm/tVPThmJX9prAH6iX8PsE4RSXfGIi8hZs= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Tzung-Bi Shih , Pierre-Louis Bossart , Mark Brown , Sasha Levin , alsa-devel@alsa-project.org Subject: [PATCH AUTOSEL 4.19 04/84] ASoC: max98090: fix possible race conditions Date: Fri, 27 Dec 2019 12:42:32 -0500 Message-Id: <20191227174352.6264-4-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20191227174352.6264-1-sashal@kernel.org> References: <20191227174352.6264-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Tzung-Bi Shih [ Upstream commit 45dfbf56975994822cce00b7475732a49f8aefed ] max98090_interrupt() and max98090_pll_work() run in 2 different threads. There are 2 possible races: Note: M98090_REG_DEVICE_STATUS = 0x01. Note: ULK == 0, PLL is locked; ULK == 1, PLL is unlocked. max98090_interrupt max98090_pll_work ---------------------------------------------- schedule max98090_pll_work restart max98090 codec receive ULK INT assert ULK == 0 schedule max98090_pll_work (1). In the case (1), the PLL is locked but max98090_interrupt unnecessarily schedules another max98090_pll_work. max98090_interrupt max98090_pll_work max98090 codec ---------------------------------------------------------------------- ULK = 1 receive ULK INT read 0x01 ULK = 0 (clear on read) schedule max98090_pll_work restart max98090 codec ULK = 1 receive ULK INT read 0x01 ULK = 0 (clear on read) read 0x01 assert ULK == 0 (2). In the case (2), both max98090_interrupt and max98090_pll_work read the same clear-on-read register. max98090_pll_work would falsely thought PLL is locked. Note: the case (2) race is introduced by the previous commit ("ASoC: max98090: exit workaround earlier if PLL is locked") to check the status and exit the loop earlier in max98090_pll_work. There are 2 possible solution options: A. turn off ULK interrupt before scheduling max98090_pll_work; and turn on again before exiting max98090_pll_work. B. remove the second thread of execution. Option A cannot fix the case (2) race because it still has 2 threads access the same clear-on-read register simultaneously. Although we could suppose the register is volatile and read the status via I2C could be much slower than the hardware raises the bits. Option B introduces a maximum 10~12 msec penalty delay in the interrupt handler. However, it could only punish the jack detection by extra 10~12 msec. Adopts option B which is the better solution overall. Signed-off-by: Tzung-Bi Shih Link: https://lore.kernel.org/r/20191122073114.219945-4-tzungbi@google.com Reviewed-by: Pierre-Louis Bossart Signed-off-by: Mark Brown Signed-off-by: Sasha Levin --- sound/soc/codecs/max98090.c | 8 ++------ sound/soc/codecs/max98090.h | 1 - 2 files changed, 2 insertions(+), 7 deletions(-) diff --git a/sound/soc/codecs/max98090.c b/sound/soc/codecs/max98090.c index 172a48d42479..f8cbed6cd0bf 100644 --- a/sound/soc/codecs/max98090.c +++ b/sound/soc/codecs/max98090.c @@ -2121,10 +2121,8 @@ static void max98090_pll_det_disable_work(struct work_struct *work) M98090_IULK_MASK, 0); } -static void max98090_pll_work(struct work_struct *work) +static void max98090_pll_work(struct max98090_priv *max98090) { - struct max98090_priv *max98090 = - container_of(work, struct max98090_priv, pll_work); struct snd_soc_component *component = max98090->component; unsigned int pll; int i; @@ -2293,7 +2291,7 @@ static irqreturn_t max98090_interrupt(int irq, void *data) if (active & M98090_ULK_MASK) { dev_dbg(component->dev, "M98090_ULK_MASK\n"); - schedule_work(&max98090->pll_work); + max98090_pll_work(max98090); } if (active & M98090_JDET_MASK) { @@ -2456,7 +2454,6 @@ static int max98090_probe(struct snd_soc_component *component) max98090_pll_det_enable_work); INIT_WORK(&max98090->pll_det_disable_work, max98090_pll_det_disable_work); - INIT_WORK(&max98090->pll_work, max98090_pll_work); /* Enable jack detection */ snd_soc_component_write(component, M98090_REG_JACK_DETECT, @@ -2509,7 +2506,6 @@ static void max98090_remove(struct snd_soc_component *component) cancel_delayed_work_sync(&max98090->jack_work); cancel_delayed_work_sync(&max98090->pll_det_enable_work); cancel_work_sync(&max98090->pll_det_disable_work); - cancel_work_sync(&max98090->pll_work); max98090->component = NULL; } diff --git a/sound/soc/codecs/max98090.h b/sound/soc/codecs/max98090.h index b1572a2d19da..388d2f74674b 100644 --- a/sound/soc/codecs/max98090.h +++ b/sound/soc/codecs/max98090.h @@ -1533,7 +1533,6 @@ struct max98090_priv { struct delayed_work jack_work; struct delayed_work pll_det_enable_work; struct work_struct pll_det_disable_work; - struct work_struct pll_work; struct snd_soc_jack *jack; unsigned int dai_fmt; int tdm_slots; -- 2.20.1