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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 636E6C64EB8 for ; Wed, 3 Oct 2018 15:54:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3505121470 for ; Wed, 3 Oct 2018 15:54:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3505121470 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727532AbeJCWnK (ORCPT ); Wed, 3 Oct 2018 18:43:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:57170 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726801AbeJCWnK (ORCPT ); Wed, 3 Oct 2018 18:43:10 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 3A2CCAD4A; Wed, 3 Oct 2018 15:54:11 +0000 (UTC) Date: Wed, 03 Oct 2018 17:54:10 +0200 Message-ID: From: Takashi Iwai To: "Jia-Ju Bai" Cc: , , , "Linux Kernel Mailing List" Subject: Re: [BUG] sound: pci: trident: a possible data race In-Reply-To: <864e211c-8be5-6a34-902a-a71f176111db@gmail.com> References: <864e211c-8be5-6a34-902a-a71f176111db@gmail.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/26 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 03 Oct 2018 14:50:25 +0200, Jia-Ju Bai wrote: > > CPU0: > snd_trident_hw_free > snd_trident_free_voice > line 3870: spin_lock_irqsave() > line 3881: voice->substream = NULL; [WRITE] > CPU1: > snd_trident_interrupt > line 3798: snd_pcm_period_elapsed(voice->substream); [READ] > > As for voice->substream, the WRITE operation in CPU0 is performed > with holding a spinlock, but the READ operation in CPU1 is performed > without holding this spinlock, so there may exist a data race. Thanks for the report. The actual crash must be very unlikely, almost 0%, though. snd_trident_hw_free() is called always after the PCM stream gets stopped via trigger callback, i.e. at the moment, there is no corresponding interrupt is generated for that voice entry. And the hardware is very old, I bet only a handful people still using in the whole world :) If we really want to be 100% sure, we may call synchronize_irq() before the NULL-clearing. But there is no way to test the bug nor the fix, so it's fairly moot, IMO. thanks, Takashi