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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 0FBB9C433E7 for ; Fri, 16 Oct 2020 09:34:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A55B2206ED for ; Fri, 16 Oct 2020 09:34:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405871AbgJPJeZ (ORCPT ); Fri, 16 Oct 2020 05:34:25 -0400 Received: from foss.arm.com ([217.140.110.172]:60794 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404835AbgJPJeZ (ORCPT ); Fri, 16 Oct 2020 05:34:25 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8869A30E; Fri, 16 Oct 2020 02:34:24 -0700 (PDT) Received: from bogus (unknown [10.57.17.164]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 43AB33F719; Fri, 16 Oct 2020 02:34:23 -0700 (PDT) Date: Fri, 16 Oct 2020 10:34:21 +0100 From: Sudeep Holla To: Jerome Brunet Cc: Ionela Voinescu , Jassi Brar , Sudeep Holla , Kevin Hilman , linux-amlogic@lists.infradead.org, Da Xue , linux-kernel@vger.kernel.org Subject: Re: [PATCH] mailbox: cancel timer before starting it Message-ID: <20201016093421.7hyiqrekiy6mtyso@bogus> References: <20200923123916.1115962-1-jbrunet@baylibre.com> <20201015134628.GA11989@arm.com> <1jlfg7k2ux.fsf@starbuckisacylon.baylibre.com> <20201015142935.GA12516@arm.com> <20201016084428.gthqj25wrvnqjsvz@bogus> <1jimbak0hh.fsf@starbuckisacylon.baylibre.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1jimbak0hh.fsf@starbuckisacylon.baylibre.com> User-Agent: NeoMutt/20171215 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 16, 2020 at 11:02:02AM +0200, Jerome Brunet wrote: > > On Fri 16 Oct 2020 at 10:44, Sudeep Holla wrote: > > > On Thu, Oct 15, 2020 at 03:29:35PM +0100, Ionela Voinescu wrote: > >> Hi Jerome, > >> > >> On Thursday 15 Oct 2020 at 15:58:30 (+0200), Jerome Brunet wrote: > >> > > >> > On Thu 15 Oct 2020 at 15:46, Ionela Voinescu wrote: > >> > > >> > > Hi guys, > >> > > > >> > > On Wednesday 23 Sep 2020 at 14:39:16 (+0200), Jerome Brunet wrote: > >> > >> If the txdone is done by polling, it is possible for msg_submit() to start > >> > >> the timer while txdone_hrtimer() callback is running. If the timer needs > >> > >> recheduling, it could already be enqueued by the time hrtimer_forward_now() > >> > >> is called, leading hrtimer to loudly complain. > >> > >> > >> > >> WARNING: CPU: 3 PID: 74 at kernel/time/hrtimer.c:932 hrtimer_forward+0xc4/0x110 > >> > >> CPU: 3 PID: 74 Comm: kworker/u8:1 Not tainted 5.9.0-rc2-00236-gd3520067d01c-dirty #5 > >> > >> Hardware name: Libre Computer AML-S805X-AC (DT) > >> > >> Workqueue: events_freezable_power_ thermal_zone_device_check > >> > >> pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--) > >> > >> pc : hrtimer_forward+0xc4/0x110 > >> > >> lr : txdone_hrtimer+0xf8/0x118 > >> > >> [...] > >> > >> > >> > >> Canceling the timer before starting it ensure that the timer callback is > >> > >> not running when the timer is started, solving this race condition. > >> > >> > >> > >> Fixes: 0cc67945ea59 ("mailbox: switch to hrtimer for tx_complete polling") > >> > >> Reported-by: Da Xue > >> > >> Signed-off-by: Jerome Brunet > >> > >> --- > >> > >> drivers/mailbox/mailbox.c | 8 ++++++-- > >> > >> 1 file changed, 6 insertions(+), 2 deletions(-) > >> > >> > >> > >> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > >> > >> index 0b821a5b2db8..34f9ab01caef 100644 > >> > >> --- a/drivers/mailbox/mailbox.c > >> > >> +++ b/drivers/mailbox/mailbox.c > >> > >> @@ -82,9 +82,13 @@ static void msg_submit(struct mbox_chan *chan) > >> > >> exit: > >> > >> spin_unlock_irqrestore(&chan->lock, flags); > >> > >> > >> > >> - if (!err && (chan->txdone_method & TXDONE_BY_POLL)) > >> > >> - /* kick start the timer immediately to avoid delays */ > >> > >> + if (!err && (chan->txdone_method & TXDONE_BY_POLL)) { > >> > >> + /* Disable the timer if already active ... */ > >> > >> + hrtimer_cancel(&chan->mbox->poll_hrt); > >> > >> + > >> > >> + /* ... and kick start it immediately to avoid delays */ > >> > >> hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); > >> > >> + } > >> > >> } > >> > >> > >> > >> static void tx_tick(struct mbox_chan *chan, int r) > >> > > > >> > > I've tracked a regression back to this commit. Details to reproduce: > >> > > >> > Hi Ionela, > >> > > >> > I don't have access to your platform and I don't get what is going on > >> > from the log below. > >> > > >> > Could you please give us a bit more details about what is going on ? > >> > > >> > >> I'm not familiar with the mailbox subsystem, so the best I can do right > >> now is to add Sudeep to Cc, in case this conflicts in some way with the > >> ARM MHU patches [1]. > >> > > > > Not it can't be doorbell driver as we use SCPI(old firmware) with upstream > > MHU driver as is limiting the number of channels to be used. > > > >> In the meantime I'll get some traces and get more familiar with the > >> code. > >> > > > > I will try that too. > > BTW, this issue was originally reported on amlogic platforms which also > use arm,mhu mailbox driver. > OK. Anyway just noticed that hrtimer_cancel uses hrtimer_try_to_cancel and hrtimer_cancel_wait_running. The latter is just cpu_relax() if PREEMPT_RT=n, so you may still have issue if the hrtimer is still active or restarts in the meantime. -- Regards, Sudeep 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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 D7FA0C433E7 for ; Fri, 16 Oct 2020 09:34:36 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 10E03206ED for ; Fri, 16 Oct 2020 09:34:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="a/QnvZRG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10E03206ED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=pFE2H6vQ/+aWXmNssYdGkVUuRSJ6TlqBU+GriNE+9f8=; b=a/QnvZRGl7UGIJuv8KhOwJogd TWcGw+uZt3sEQdh9I/2k+2ZODsqEST6YE3t+kh7IoV+uw5uiSf8s+u6AW2t3G8jWUUUMfyFpJCzSC atO791JXoBF+e236JeYjUZ46Z2XUX07M4H3Xqt0vdtkG59n37fu8cgMlsy7Fw0BLr/eXHFIPoo9Rz 3yjPKUVJeotD1ZRBN/7g/z8u8Aj1RaCLEuv9cZoELlwgbEjoY9PaREAXSbl8EdaKPwRyIZC9ry88U 6mQ+sTpw/s9uHF9FNSq/7+b+9vUB12C+V2lIAp5fv0juoWNdPN4PJtIQj/lfmzXG/VllRIgr7Wmg4 hpLDw/fDg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kTM85-0002e6-Kb; Fri, 16 Oct 2020 09:34:29 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kTM83-0002dN-Ab for linux-amlogic@lists.infradead.org; Fri, 16 Oct 2020 09:34:28 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8869A30E; Fri, 16 Oct 2020 02:34:24 -0700 (PDT) Received: from bogus (unknown [10.57.17.164]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 43AB33F719; Fri, 16 Oct 2020 02:34:23 -0700 (PDT) Date: Fri, 16 Oct 2020 10:34:21 +0100 From: Sudeep Holla To: Jerome Brunet Subject: Re: [PATCH] mailbox: cancel timer before starting it Message-ID: <20201016093421.7hyiqrekiy6mtyso@bogus> References: <20200923123916.1115962-1-jbrunet@baylibre.com> <20201015134628.GA11989@arm.com> <1jlfg7k2ux.fsf@starbuckisacylon.baylibre.com> <20201015142935.GA12516@arm.com> <20201016084428.gthqj25wrvnqjsvz@bogus> <1jimbak0hh.fsf@starbuckisacylon.baylibre.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1jimbak0hh.fsf@starbuckisacylon.baylibre.com> User-Agent: NeoMutt/20171215 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201016_053427_467039_5CB5554B X-CRM114-Status: GOOD ( 36.00 ) X-BeenThere: linux-amlogic@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Hilman , Jassi Brar , linux-kernel@vger.kernel.org, Sudeep Holla , linux-amlogic@lists.infradead.org, Ionela Voinescu , Da Xue Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-amlogic" Errors-To: linux-amlogic-bounces+linux-amlogic=archiver.kernel.org@lists.infradead.org On Fri, Oct 16, 2020 at 11:02:02AM +0200, Jerome Brunet wrote: > > On Fri 16 Oct 2020 at 10:44, Sudeep Holla wrote: > > > On Thu, Oct 15, 2020 at 03:29:35PM +0100, Ionela Voinescu wrote: > >> Hi Jerome, > >> > >> On Thursday 15 Oct 2020 at 15:58:30 (+0200), Jerome Brunet wrote: > >> > > >> > On Thu 15 Oct 2020 at 15:46, Ionela Voinescu wrote: > >> > > >> > > Hi guys, > >> > > > >> > > On Wednesday 23 Sep 2020 at 14:39:16 (+0200), Jerome Brunet wrote: > >> > >> If the txdone is done by polling, it is possible for msg_submit() to start > >> > >> the timer while txdone_hrtimer() callback is running. If the timer needs > >> > >> recheduling, it could already be enqueued by the time hrtimer_forward_now() > >> > >> is called, leading hrtimer to loudly complain. > >> > >> > >> > >> WARNING: CPU: 3 PID: 74 at kernel/time/hrtimer.c:932 hrtimer_forward+0xc4/0x110 > >> > >> CPU: 3 PID: 74 Comm: kworker/u8:1 Not tainted 5.9.0-rc2-00236-gd3520067d01c-dirty #5 > >> > >> Hardware name: Libre Computer AML-S805X-AC (DT) > >> > >> Workqueue: events_freezable_power_ thermal_zone_device_check > >> > >> pstate: 20000085 (nzCv daIf -PAN -UAO BTYPE=--) > >> > >> pc : hrtimer_forward+0xc4/0x110 > >> > >> lr : txdone_hrtimer+0xf8/0x118 > >> > >> [...] > >> > >> > >> > >> Canceling the timer before starting it ensure that the timer callback is > >> > >> not running when the timer is started, solving this race condition. > >> > >> > >> > >> Fixes: 0cc67945ea59 ("mailbox: switch to hrtimer for tx_complete polling") > >> > >> Reported-by: Da Xue > >> > >> Signed-off-by: Jerome Brunet > >> > >> --- > >> > >> drivers/mailbox/mailbox.c | 8 ++++++-- > >> > >> 1 file changed, 6 insertions(+), 2 deletions(-) > >> > >> > >> > >> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > >> > >> index 0b821a5b2db8..34f9ab01caef 100644 > >> > >> --- a/drivers/mailbox/mailbox.c > >> > >> +++ b/drivers/mailbox/mailbox.c > >> > >> @@ -82,9 +82,13 @@ static void msg_submit(struct mbox_chan *chan) > >> > >> exit: > >> > >> spin_unlock_irqrestore(&chan->lock, flags); > >> > >> > >> > >> - if (!err && (chan->txdone_method & TXDONE_BY_POLL)) > >> > >> - /* kick start the timer immediately to avoid delays */ > >> > >> + if (!err && (chan->txdone_method & TXDONE_BY_POLL)) { > >> > >> + /* Disable the timer if already active ... */ > >> > >> + hrtimer_cancel(&chan->mbox->poll_hrt); > >> > >> + > >> > >> + /* ... and kick start it immediately to avoid delays */ > >> > >> hrtimer_start(&chan->mbox->poll_hrt, 0, HRTIMER_MODE_REL); > >> > >> + } > >> > >> } > >> > >> > >> > >> static void tx_tick(struct mbox_chan *chan, int r) > >> > > > >> > > I've tracked a regression back to this commit. Details to reproduce: > >> > > >> > Hi Ionela, > >> > > >> > I don't have access to your platform and I don't get what is going on > >> > from the log below. > >> > > >> > Could you please give us a bit more details about what is going on ? > >> > > >> > >> I'm not familiar with the mailbox subsystem, so the best I can do right > >> now is to add Sudeep to Cc, in case this conflicts in some way with the > >> ARM MHU patches [1]. > >> > > > > Not it can't be doorbell driver as we use SCPI(old firmware) with upstream > > MHU driver as is limiting the number of channels to be used. > > > >> In the meantime I'll get some traces and get more familiar with the > >> code. > >> > > > > I will try that too. > > BTW, this issue was originally reported on amlogic platforms which also > use arm,mhu mailbox driver. > OK. Anyway just noticed that hrtimer_cancel uses hrtimer_try_to_cancel and hrtimer_cancel_wait_running. The latter is just cpu_relax() if PREEMPT_RT=n, so you may still have issue if the hrtimer is still active or restarts in the meantime. -- Regards, Sudeep _______________________________________________ linux-amlogic mailing list linux-amlogic@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-amlogic