From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3199923-1518625230-2-13167421394106839461 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no ("Email failed DMARC policy for domain") X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.001, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', FromHeader='uk', MailFrom='org' X-Spam-charsets: plain='UTF-8' X-IgnoreVacation: yes ("Email failed DMARC policy for domain") X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: stable-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1518625230; b=Hb3d9ESpmKRo931LYAoolGmRN+uC9YJ6CKMUd6iBq4iKmN7 eq0Ych6xzfXxz9F3YIFEAG2aWuYCyQu6CD2fTqAj1/dI+CEtvUFow9qDfTxdSR39 mSGYt7vtUXvvxe9IHHDEp+ljx45d2nk2ABVUKHgCx4uwrQWyOmcmlVdRAqJUU/pC vA6gvAnje8KcXhNdOcYLicpcqpP9a4GdD2vKrL78gt/aI0wjLDVM5qBCYswLWwiN B1rFF4cwvo3FiEqgDRK8+r5A9EyaaTbfzVQ9/tuuuDcTpt9tRLMJEqR7GP7LRSzL 1UJttKmSqoCVIGOBvKP3Spsrlcbpn90ZaWHs2cw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=message-id:subject:from:to:cc:date :in-reply-to:references:content-type:mime-version :content-transfer-encoding:sender:list-id; s=arctest; t= 1518625230; bh=vdrvJRGadUbGDZ4Z74E5eYspCYNSVQwkXNmZ4/+fuf8=; b=I TK872bnArWFZXDGq0rq3H+HfjBLjxQGebJq5p6PMwCLYlIRIL4D5vHmAP7wfzmAa 4CQd2okrgZcYxzZI1SjR/ecrGKQ8dOzpNOER+pxp4XqzkZQYUjnhSkjGFkCyzvmV Gff2+kJZdRX239YDO1ZGlZXTsWG3Aon4mfXJwAksdlxpT1b/A/gQgacU8qLnq0x5 G//zNhD/g8r1PKjSby3HILn8Y/pqsIBDempsasNwvoDeUWua8fPxrmjaiGaNJz4h jdAPUvXU993+k2l9VlksubN+PHst4vFEKl2U6bRYLAztGQUhdzrDzW611W+LrJAu 3rmkJT+AjEoDlLQeC21ag== ARC-Authentication-Results: i=1; mx3.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=codethink.co.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=codethink.co.uk header.result=pass header_is_org_domain=yes Authentication-Results: mx3.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,has-list-id=yes,d=none) header.from=codethink.co.uk; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=stable-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=codethink.co.uk header.result=pass header_is_org_domain=yes Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1032206AbeBNQU1 (ORCPT ); Wed, 14 Feb 2018 11:20:27 -0500 Received: from imap1.codethink.co.uk ([176.9.8.82]:55252 "EHLO imap1.codethink.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1032203AbeBNQU0 (ORCPT ); Wed, 14 Feb 2018 11:20:26 -0500 Message-ID: <1518625223.3422.19.camel@codethink.co.uk> Subject: Re: [PATCH 4.4 20/87] ALSA: pcm: Allow aborting mutex lock at OSS read/write loops From: Ben Hutchings To: Takashi Iwai Cc: stable@vger.kernel.org, Greg Kroah-Hartman , LKML Date: Wed, 14 Feb 2018 16:20:23 +0000 In-Reply-To: References: <20180115123349.252309699@linuxfoundation.org> <20180115123351.309626066@linuxfoundation.org> <1516750548.3417.34.camel@codethink.co.uk> Organization: Codethink Ltd. Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6-1+deb9u1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Mon, 2018-02-12 at 09:34 +0100, Takashi Iwai wrote: > On Wed, 24 Jan 2018 00:35:48 +0100, > Ben Hutchings wrote: > > > > On Mon, 2018-01-15 at 13:34 +0100, Greg Kroah-Hartman wrote: > > > 4.4-stable review patch.  If anyone has any objections, please let me know. > > > > > > ------------------ > > > > > > From: Takashi Iwai > > > > > > commit 900498a34a3ac9c611e9b425094c8106bdd7dc1c upstream. > > > > > > PCM OSS read/write loops keep taking the mutex lock for the whole > > > read/write, and this might take very long when the exceptionally high > > > amount of data is given.  Also, since it invokes with mutex_lock(), > > > the concurrent read/write becomes unbreakable. > > > > > > This patch tries to address these issues by replacing mutex_lock() > > > with mutex_lock_interruptible(), and also splits / re-takes the lock > > > at each read/write period chunk, so that it can switch the context > > > more finely if requested. > > > > [...] > > > @@ -1414,18 +1417,18 @@ static ssize_t snd_pcm_oss_write1(struct > > >   xfer += tmp; > > >   if ((substream->f_flags & O_NONBLOCK) != 0 && > > >       tmp != runtime->oss.period_bytes) > > > - break; > > > + tmp = -EAGAIN; > > >   } > > > + err: > > > + mutex_unlock(&runtime->oss.params_lock); > > > + if (tmp < 0) > > > + break; > > >   if (signal_pending(current)) { > > >   tmp = -ERESTARTSYS; > > > - goto err; > > > + break; > > >   } > > > + tmp = 0; > > >   } > > > - mutex_unlock(&runtime->oss.params_lock); > > > - return xfer; > > > - > > > - err: > > > - mutex_unlock(&runtime->oss.params_lock); > > >   return xfer > 0 ? (snd_pcm_sframes_t)xfer : tmp; > > >  } > > > > [...] > > > > Some of the "goto err" statements in the loop are conditional on tmp <= > > 0, but if tmp == 0 this will no longer terminate the loop.  Is that > > intentional or a bug? > > The patch rather fixes the endless loop: the signal_pending() check is > added after goto err, so that it aborts the loop properly. Let me rephrase then: if snd_pcm_oss_write2() returns 0, does that imply that signal_pending() is true? If there is any other reason that it could return 0, then this appears to introduce a bug. Ben. -- Ben Hutchings Software Developer, Codethink Ltd.