From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750976AbaLPLfT (ORCPT ); Tue, 16 Dec 2014 06:35:19 -0500 Received: from service87.mimecast.com ([91.220.42.44]:59167 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750814AbaLPLfR convert rfc822-to-8bit (ORCPT ); Tue, 16 Dec 2014 06:35:17 -0500 Date: Tue, 16 Dec 2014 11:36:02 +0000 From: Sudeep Holla To: Ashwin Chaugule Cc: "jaswinder.singh@linaro.org" , "arnd@arndb.de" , "patches@linaro.org" , "linaro-acpi@lists.linaro.org" , "linux-kernel@vger.kernel.org" , "broonie@kernel.org" , "linux-arm-kernel@lists.infradead.org" , Sudeep Holla Subject: Re: [Linaro-acpi] [PATCH] Mailbox: Complete wait event only if Tx was successful Message-ID: <20141216113602.GA21888@e103737-lin.cambridge.arm.com> References: <1418242572-20998-1-git-send-email-ashwin.chaugule@linaro.org> <548AAA95.6020001@arm.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginalArrivalTime: 16 Dec 2014 11:35:12.0393 (UTC) FILETIME=[5AA38F90:01D01924] X-MC-Unique: 114121611351402201 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 12, 2014 at 05:47:26PM +0000, Ashwin Chaugule wrote: > On 12 December 2014 at 03:43, Sudeep Holla wrote: > > Hi Ashwin, > > Hi, > Hi Ashwin, > > On Thursday 11 December 2014 01:46 AM, Ashwin Chaugule wrote: > >> > >> If a wait_for_completion_timeout() call returns due to a timeout, > >> the mbox code can still call complete() after returning from the wait. > >> This can cause subsequent transmissions on a channel to fail, since > >> the wait_for_completion_timeout() sees the completion variable > >> is !=0, caused by the erroneous complete() call, and immediately > >> returns without waiting for the time as expected by the client. > >> > >> Fix this by calling complete() only if the TX was successful. > >> > >> Signed-off-by: Ashwin Chaugule > >> --- > >> drivers/mailbox/mailbox.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > >> index 17e9e4a..4acaddb 100644 > >> --- a/drivers/mailbox/mailbox.c > >> +++ b/drivers/mailbox/mailbox.c > >> @@ -101,7 +101,7 @@ static void tx_tick(struct mbox_chan *chan, int r) > >> if (mssg && chan->cl->tx_done) > >> chan->cl->tx_done(chan->cl, mssg, r); > >> > >> - if (chan->cl->tx_block) > >> + if ((!r) && chan->cl->tx_block) > >> complete(&chan->tx_complete); > > > > > > Just curious to check if there's another possible race which is > > a different issue. > > > > Suppose the timer fired and indicated that the Tx is complete, then > > it tries to execute complete while the wait_for_completion_timeout timed > > out. Does that make sense ? > > > > So if yes, how about adding !completion_done(..) to the check while you > > are at this ? > > Yea. Seems like another race condition. I'll add it along with this.. > Thanks ! Regards, Sudeep