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=-8.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,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 6128AC433FE for ; Fri, 11 Dec 2020 17:38:28 +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 4C8FA23EF1 for ; Fri, 11 Dec 2020 17:38:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4C8FA23EF1 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 B4DE31736; Fri, 11 Dec 2020 18:37:34 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa0.perex.cz B4DE31736 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=alsa-project.org; s=default; t=1607708304; bh=scZyuOwh5JCvAVl4fPzI299iEK/8Q7Mb/gXsWUJjp4k=; h=Date:From:To:Subject:In-Reply-To:References:Cc:List-Id: List-Unsubscribe:List-Archive:List-Post:List-Help:List-Subscribe: From; b=cuWwPv8iXZVrkR9QgxAwOeoENew5FTARyRctFGDtLIsW7OKmyBIiCE5N7mZXfD2yD PGPr8ZvI2VsUA5INfYjjUWzS5A5AzkZ3CDdK4LlbZAlmy9gVE/i1F9uM0od7JmUTVK z8dUiWJQcRgjRQUsLYxfNB46Z+vg0GUofUBE5ukk= Received: from alsa1.perex.cz (localhost.localdomain [127.0.0.1]) by alsa1.perex.cz (Postfix) with ESMTP id 3C144F80217; Fri, 11 Dec 2020 18:37:34 +0100 (CET) Received: by alsa1.perex.cz (Postfix, from userid 50401) id C38CFF8021D; Fri, 11 Dec 2020 18:37:32 +0100 (CET) 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 602D0F8014E for ; Fri, 11 Dec 2020 18:37:30 +0100 (CET) DKIM-Filter: OpenDKIM Filter v2.11.0 alsa1.perex.cz 602D0F8014E 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 EB0B1AE4A; Fri, 11 Dec 2020 17:37:29 +0000 (UTC) Date: Fri, 11 Dec 2020 18:37:29 +0100 Message-ID: From: Takashi Iwai To: Jaroslav Kysela Subject: Re: [PATCH] alsactl: Skip restore during the lock In-Reply-To: References: <20201211083804.800-1-tiwai@suse.de> 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 development 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 Fri, 11 Dec 2020 18:23:03 +0100, Jaroslav Kysela wrote: > > Dne 11. 12. 20 v 18:06 Takashi Iwai napsal(a): > > On Fri, 11 Dec 2020 17:59:05 +0100, > > Takashi Iwai wrote: > >> > >> On Fri, 11 Dec 2020 17:45:45 +0100, > >> Jaroslav Kysela wrote: > >>> > >>> Dne 11. 12. 20 v 9:38 Takashi Iwai napsal(a): > >>>> Currently alsactl-restore tries to initialize the device when an error > >>>> is found for restore action. But this isn't the right behavior in the > >>>> case where the lock is held; it implies that another alsactl is > >>>> running concurrently, hence you shouldn't initialize the card at the > >>>> same time. The situation is found easily when two alsactls get > >>>> started by both udev and systemd (note that those two invocations are > >>>> the designed behavior, see /usr/lib/udev/rules.d/78-sound-cards.rules > >>>> for details). > >>>> > >>>> This patch changes load_state() not to handle the initialization if > >>>> the locking fails. > >>> > >>> The operation should serialize in this case (there's limit of 10 seconds which > >>> should be enough to finish the initialization). The state_lock() function > >>> should return -EBUSY when the file is locked (and I'm fine to change the > >>> behaviour from 'init' to 'skip' for this lock state). > >>> > >>> It seems that -EEXIST is returned when the lock file exists, but the > >>> open(file, O_CREAT|O_EXCL, 0644) caller has not enough priviledges to access > >>> this file when another user owns the file. > >>> > >>> But alsactl from /lib/udev/rules.d/90-alsa-restore.rules and > >>> /lib/systemd/system/alsa-restore.service should be run as root, right? > >> > >> Yes, it should be root. > >> > >> I also wondered how EEXIST comes, too. Maybe it's also the race > >> between the first open(O_RDWR) and the second > >> open(O_RDWR|O_CREAT|O_EXCL)? If so, it'd be better to go back again > >> to the normal open(O_RDWR)? > > > > ... something like below > > > > > > diff --git a/alsactl/lock.c b/alsactl/lock.c > > index 4a485392b3bd..c1c30f0c5eee 100644 > > --- a/alsactl/lock.c > > +++ b/alsactl/lock.c > > @@ -64,6 +64,9 @@ static int state_lock_(const char *file, int lock, int timeout, int _fd) > > if (errno == EBUSY || errno == EAGAIN) { > > sleep(1); > > timeout--; > > + } if (errno == EEXIST){ > > + /* race at creating a lock, try again */ > > + continue; > > } else { > > err = -errno; > > goto out; > > If we don't use the sleep call and the timeout counter, there's endless CPU > busy loop when the root creates the lock file and user wants to access it for > example. It's better to add EEXIST to the previous errno condition. The timeout is decreased in the while condition. Takashi