From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755235AbcKJBxX (ORCPT ); Wed, 9 Nov 2016 20:53:23 -0500 Received: from mail-qk0-f194.google.com ([209.85.220.194]:34799 "EHLO mail-qk0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754797AbcKJBxV (ORCPT ); Wed, 9 Nov 2016 20:53:21 -0500 MIME-Version: 1.0 In-Reply-To: <1478740868-55269-1-git-send-email-briannorris@chromium.org> References: <1477584334-39956-1-git-send-email-briannorris@chromium.org> <1478740868-55269-1-git-send-email-briannorris@chromium.org> From: "Rafael J. Wysocki" Date: Thu, 10 Nov 2016 02:53:20 +0100 X-Google-Sender-Auth: jC02fizYBwwTNwRvvek2JEPXDrs Message-ID: Subject: Re: [PATCH v3] PM / sleep: don't suspend parent when async child suspend_{noirq,late} fails To: Brian Norris Cc: "Rafael J . Wysocki" , Pavel Machek , Len Brown , Greg Kroah-Hartman , Linux Kernel Mailing List , Doug Anderson , Brian Norris , Jeffy Chen , Linux PM , Chuansheng Liu , Dmitry Torokhov 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 Thu, Nov 10, 2016 at 2:21 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 doing our error and wakeup checking > (particularly, for the async_error flag) after waiting for children to > suspend, instead of before. This also helps align the logic for the noirq and > late suspend cases with the logic in __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 > --- > v2: s/early/late/ in commit message > > v3: > * drop patch 1, as the callback-printing is unrelated, semi-controversial, and > might break existing (but poor -- c'mon, since when do tools get to rely on > kernel messages?) tools > * do all error checking after dpm_wait_for_children() -- this helps make > things consistent and reduces duplication. > * drop Dmitry's Reviewed-by, since the patch changed enough > > drivers/base/power/main.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/base/power/main.c b/drivers/base/power/main.c > index c58563581345..57a8ca4bc8ab 100644 > --- a/drivers/base/power/main.c > +++ b/drivers/base/power/main.c > @@ -1027,6 +1027,8 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a > TRACE_DEVICE(dev); > TRACE_SUSPEND(0); > > + dpm_wait_for_children(dev, async); > + On a second thought. I'd move the if (dev->power.syscore || dev->power.direct_complete) along with this (and put it in front), because those flags won't change while children are being waited on anyway. > if (async_error) > goto Complete; > > @@ -1038,8 +1040,6 @@ static int __device_suspend_noirq(struct device *dev, pm_message_t state, bool a > if (dev->power.syscore || dev->power.direct_complete) > goto Complete; > > - dpm_wait_for_children(dev, async); > - > if (dev->pm_domain) { > info = "noirq power domain "; > callback = pm_noirq_op(&dev->pm_domain->ops, state); > @@ -1174,6 +1174,8 @@ static int __device_suspend_late(struct device *dev, pm_message_t state, bool as > > __pm_runtime_disable(dev, false); > > + dpm_wait_for_children(dev, async); > + And analogously here. > if (async_error) > goto Complete; > > @@ -1185,8 +1187,6 @@ static int __device_suspend_late(struct device *dev, pm_message_t state, bool as > if (dev->power.syscore || dev->power.direct_complete) > goto Complete; > > - dpm_wait_for_children(dev, async); > - > if (dev->pm_domain) { > info = "late power domain "; > callback = pm_late_early_op(&dev->pm_domain->ops, state); Thanks, Rafael