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 0C53DC433DF for ; Fri, 16 Oct 2020 08:44:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A77E920848 for ; Fri, 16 Oct 2020 08:44:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394754AbgJPIoi (ORCPT ); Fri, 16 Oct 2020 04:44:38 -0400 Received: from foss.arm.com ([217.140.110.172]:59382 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2394727AbgJPIoh (ORCPT ); Fri, 16 Oct 2020 04:44:37 -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 3982330E; Fri, 16 Oct 2020 01:44:36 -0700 (PDT) Received: from bogus (unknown [10.57.17.164]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0FA0F3F66B; Fri, 16 Oct 2020 01:44:34 -0700 (PDT) Date: Fri, 16 Oct 2020 09:44:28 +0100 From: Sudeep Holla To: Ionela Voinescu Cc: Jerome Brunet , Jassi Brar , 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: <20201016084428.gthqj25wrvnqjsvz@bogus> References: <20200923123916.1115962-1-jbrunet@baylibre.com> <20201015134628.GA11989@arm.com> <1jlfg7k2ux.fsf@starbuckisacylon.baylibre.com> <20201015142935.GA12516@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201015142935.GA12516@arm.com> User-Agent: NeoMutt/20171215 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Regards, Sudeep