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=-3.7 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 57405C433DF for ; Thu, 9 Jul 2020 11:02:05 +0000 (UTC) Received: from alsa0.perex.cz (alsa0.perex.cz [77.48.224.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D84D92076A for ; Thu, 9 Jul 2020 11:02:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alsa-project.org header.i=@alsa-project.org header.b="jEQGGCTU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D84D92076A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=alsa-devel-bounces@alsa-project.org Received: from alsa1.perex.cz (alsa1.perex.cz [207.180.221.201]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa0.perex.cz (Postfix) with ESMTPS id 5E7FE1665; Thu, 9 Jul 2020 13:01:13 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz 5E7FE1665 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1594292523; bh=ENh+iCnDazdjaIkKOVzUEriYbU03fExfpv9WryD8da4=; h=Date:From:To:Subject:In-Reply-To:References:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=jEQGGCTUk1Pq0mYgbXU7R5cUDCYFrKcWg2YLcxvD8sxs5TvI++I2EoqjPdr2AtcwP AC90+72oOfhsAcXbFMFHvxTREzaIm0mLoLyalMp7iiNQIxPpJ3pIxNWOr9kF+fRN+o Jy8ndC34kFXlqPpZJUCYJP/kafYTlNfnQ7GqZ7Yw= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id A0EB4F802BC; Thu, 9 Jul 2020 13:00:30 +0200 (CEST) Received: by alsa1.perex.cz (Postfix, from userid 50401) id 52ABCF802BD; Thu, 9 Jul 2020 13:00:28 +0200 (CEST) Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by alsa1.perex.cz (Postfix) with ESMTPS id 2C302F800AE for ; Thu, 9 Jul 2020 13:00:22 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 2C302F800AE X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 72436AE44; Thu, 9 Jul 2020 11:00:21 +0000 (UTC) Date: Thu, 09 Jul 2020 13:00:21 +0200 Message-ID: From: Takashi Iwai To: Mark Hills Subject: Re: [PATCH 2/5] echoaudio: Race conditions around "opencount" In-Reply-To: <20200708101848.3457-2-mark@xwax.org> References: <2007081115280.3085@stax.localdomain> <20200708101848.3457-2-mark@xwax.org> 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/25.3 (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 Cc: alsa-devel@alsa-project.org X-BeenThere: alsa-devel@alsa-project.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: "Alsa-devel" On Wed, 08 Jul 2020 12:18:45 +0200, Mark Hills wrote: > > Use of atomics does not make these statements robust: > > atomic_inc(&chip->opencount); > if (atomic_read(&chip->opencount) > 1 && chip->rate_set) > chip->can_set_rate=0; > > and > > if (atomic_read(&chip->opencount)) { > if (chip->opencount) { > changed = -EAGAIN; > } else { > changed = set_digital_mode(chip, dmode); > > It would be necessary to atomically increment or decrement the value > and use the returned result. And yet we still need to prevent other > threads making use of "can_set_rate" while we set it. > > However in all but one case the atomic is misleading as they are already > running with "mode_mutex" held. > > Decisions are made on mode setting are often intrinsically connected > to "opencount" because some operations are not permitted unless > there is sole ownership. > > So instead simplify this, and use "mode_mutex" as a lock for all reference > counting and mode setting. > > Signed-off-by: Mark Hills Applied now. Thanks. Takashi