From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755404AbcKBDn6 (ORCPT ); Tue, 1 Nov 2016 23:43:58 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:54111 "HELO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751063AbcKBDn5 (ORCPT ); Tue, 1 Nov 2016 23:43:57 -0400 From: "Rafael J. Wysocki" To: Dmitry Torokhov Cc: Brian Norris , Pavel Machek , Len Brown , Greg Kroah-Hartman , lkml , Doug Anderson , Brian Norris , Jeffy Chen , "linux-pm@vger.kernel.org" , Chuansheng Liu Subject: Re: [PATCH v2 2/2] PM / sleep: don't suspend parent when async child suspend_{noirq,late} fails Date: Wed, 02 Nov 2016 04:51:08 +0100 Message-ID: <50971906.K6xak2t6Z6@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.9.0-rc2+; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1476923170-111986-2-git-send-email-briannorris@chromium.org> <8017823.VJuZzSqtaY@vostro.rjw.lan> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, November 01, 2016 12:04:28 AM Dmitry Torokhov wrote: > On Mon, Oct 31, 2016 at 10:25 PM, Rafael J. Wysocki wrote: > > On Thursday, October 27, 2016 09:05:34 AM Brian Norris wrote: > >> Consider two devices, A and B, where B is a child of A, and B utilizes > >> asynchronous suspend (it does not matter whether A is sync or async). If > >> B fails to suspend_noirq() or suspend_late(), or is interrupted by a > >> wakeup (pm_wakeup_pending()), then it aborts and sets the async_error > >> variable. However, device A does not (immediately) check the async_error > >> variable; it may continue to run its own suspend_noirq()/suspend_late() > >> callback. This is bad. > >> > >> We can resolve this problem by checking the async_error flag after > >> waiting for children to suspend, using the same logic for the noirq and > >> late suspend cases as we already do for __device_suspend(). > >> > >> It's easy to observe this erroneous behavior by, for example, forcing a > >> device to sleep a bit in its suspend_noirq() (to ensure the parent is > >> waiting for the child to complete), then return an error, and watch the > >> parent suspend_noirq() still get called. (Or similarly, fake a wakeup > >> event at the right (or is it wrong?) time.) > >> > >> Fixes: de377b397272 ("PM / sleep: Asynchronous threads for suspend_late") > >> Fixes: 28b6fd6e3779 ("PM / sleep: Asynchronous threads for suspend_noirq") > >> Reported-by: Jeffy Chen > >> Signed-off-by: Brian Norris > >> Reviewed-by: Dmitry Torokhov > >> --- > >> v2: s/early/late/ in commit message > >> > >> drivers/base/power/main.c | 6 ++++++ > >> 1 file changed, 6 insertions(+) > >> > >> diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > >> index c58563581345..eaf6b53463a5 100644 > >> --- a/drivers/base/power/main.c > >> +++ b/drivers/base/power/main.c > >> @@ -1040,6 +1040,9 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a > >> > >> dpm_wait_for_children(dev, async); > >> > >> + if (async_error) > >> + goto Complete; > >> + > > > > This is a second chech for async_error in this routine and is the first one > > really needed after adding this? > > There is really no point in waiting for children to be suspended if > error has already been signalled; that's what first check achieves. > The 2nd check ensures that we abort suspend if any of the children > failed to suspend. > > I'd say both checks are needed (well, 1st is helpful, 2nd is essential). OK, fair enough. Thanks, Rafael