From mboxrd@z Thu Jan 1 00:00:00 1970 From: Brian Norris Subject: Re: [PATCH 2/2] PM / sleep: don't suspend parent when async child suspend_{noirq,early} fails Date: Wed, 19 Oct 2016 17:46:11 -0700 Message-ID: <20161020004610.GC78840@google.com> References: <1476923170-111986-1-git-send-email-briannorris@chromium.org> <1476923170-111986-2-git-send-email-briannorris@chromium.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <1476923170-111986-2-git-send-email-briannorris@chromium.org> Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J . Wysocki" , Pavel Machek , Len Brown , Greg Kroah-Hartman Cc: linux-kernel@vger.kernel.org, Doug Anderson , Brian Norris , Jeffy Chen , linux-pm@vger.kernel.org, Chuansheng Liu , Dmitry Torokhov List-Id: linux-pm@vger.kernel.org Ugh, as I hope the patch context makes clear, the subject should be s/early/late/ as should the body of the commit message. On Wed, Oct 19, 2016 at 05:26:10PM -0700, 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_early(), or is interrupted by a s/early/late/ > 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_early() s/early/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 If the patch is otherwise acceptable, feel free to make the above edits. Or I can fix them up if I send v2. Sorry for the noise, Brian