From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grygorii Strashko Subject: Re: [PATCH 1/2] PM / sleep: ensure deferred probe workqueue is finished in wait_for_device_probe Date: Tue, 13 Oct 2015 21:25:28 +0300 Message-ID: <561D4C98.9070002@ti.com> References: <5617D155.60700@ti.com> <2953623.dd2aFp1rBS@vostro.rjw.lan> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from comal.ext.ti.com ([198.47.26.152]:42198 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750984AbbJMSZl (ORCPT ); Tue, 13 Oct 2015 14:25:41 -0400 In-Reply-To: <2953623.dd2aFp1rBS@vostro.rjw.lan> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: "Rafael J. Wysocki" Cc: Alan Stern , Greg Kroah-Hartman , Pavel Machek , Len Brown , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Thierry Reding On 10/10/2015 12:16 AM, Rafael J. Wysocki wrote: > On Friday, October 09, 2015 09:38:13 AM Grygorii Strashko wrote: >> On 10/08/2015 03:53 PM, Alan Stern wrote: >>> On Thu, 8 Oct 2015, Rafael J. Wysocki wrote: >>> >>>>> @@ -391,6 +391,10 @@ int driver_probe_done(void) >>>>> */ >>>>> void wait_for_device_probe(void) >>>>> { >>>>> + /* wait for the deferred probe workqueue to finish */ >>>>> + if (driver_deferred_probe_enable) >>>>> + flush_workqueue(deferred_wq); >>>>> + >>>>> /* wait for the known devices to complete their probing */ >>>>> wait_event(probe_waitqueue, atomic_read(&probe_count) == 0); >>>>> async_synchronize_full(); >>>> >>>> I'm not sure if this is sufficient. >>>> >>>> Something may be added to the workqueue right after you've flushed it and >>>> then be reporobed after the wait_event() in theory. Or am I missing anything? >>> >>> Maybe I'm missing part of this, but I think the point is to make sure >>> that every probe which began or was queued before this function got >>> called, has finished before the function returns. >>> >>> Thus, in the case at hand we want to defer all probes starting from >>> some point in the system sleep transition. Grygorii sets his >>> defer_all_probes variable and then calls this function. It waits for >>> any probes that were initiated before the function call. Any probe >>> that was initiated after the function call (for example, the ones >>> you're concerned about between the flush_workqueue and wait_event) will >>> see that defer_all_probes is set and so will defer itself. >> >> Yes. It will work as expected with the next patch. >> For all other case, where this API is used alone - >> it will make things more safe, but there is no way to completely block >> scheduling of new probes. > > Well, in that case why don't you make it part of the second patch after all > instead of making a false impression of fixing a more general problem? > ok. -- regards, -grygorii