Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751803AbbERAVt (ORCPT ); Sun, 17 May 2015 20:21:49 -0400 Received: from v094114.home.net.pl ([79.96.170.134]:50147 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751208AbbERAVn (ORCPT ); Sun, 17 May 2015 20:21:43 -0400 From: "Rafael J. Wysocki" To: Jin Qian Cc: Len Brown , Pavel Machek , Greg Kroah-Hartman , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] power: increment wakeup_count when save_wakeup_count failed. Date: Mon, 18 May 2015 02:47:01 +0200 Message-ID: <4311490.ZRNbV6fRsK@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.0.0+; KDE/4.11.5; x86_64; ; ) In-Reply-To: References: <1429750212-28659-1-git-send-email-jinqian@android.com> <6356516.qkiSo3Mux2@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 Content-Length: 3861 Lines: 100 On Friday, May 15, 2015 06:08:32 PM Jin Qian wrote: > Some wakeup event happens every frequently between reading > wakeup_count and writing back wakeup_count. > They changed wakeup event count so writes fail and usespace doesn't > continue to suspend. However, such > occurrences are not counted in ws->wakeup_count. So I hope you've read the comment in wakeup_source_report_event(). > I spent quite sometime finding out the problematic wakeup > event with inaccurate wakeup_count : ) But your patch doesn't fix the problem. ws->wakeup_count is still racy and kind of even more after the patch than before. > On Fri, May 15, 2015 at 5:34 PM, Rafael J. Wysocki wrote: > > On Wednesday, April 22, 2015 05:50:11 PM Jin Qian wrote: > >> user-space aborts suspend attempt if writing wakeup_count failed. > >> Count the write failure towards wakeup_count. > > > > A use case, please? > > > >> Signed-off-by: Jin Qian > >> --- > >> drivers/base/power/wakeup.c | 17 +++++++++++++++++ > >> 1 file changed, 17 insertions(+) > >> > >> diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c > >> index f24c622..bdb45f3 100644 > >> --- a/drivers/base/power/wakeup.c > >> +++ b/drivers/base/power/wakeup.c > >> @@ -57,6 +57,8 @@ static LIST_HEAD(wakeup_sources); > >> > >> static DECLARE_WAIT_QUEUE_HEAD(wakeup_count_wait_queue); > >> > >> +static ktime_t last_read_time; > >> + > >> /** > >> * wakeup_source_prepare - Prepare a new wakeup source for initialization. > >> * @ws: Wakeup source to prepare. > >> @@ -771,10 +773,15 @@ void pm_wakeup_clear(void) > >> bool pm_get_wakeup_count(unsigned int *count, bool block) > >> { > >> unsigned int cnt, inpr; > >> + unsigned long flags; > >> > >> if (block) { > >> DEFINE_WAIT(wait); > >> > >> + spin_lock_irqsave(&events_lock, flags); > >> + last_read_time = ktime_get(); > >> + spin_unlock_irqrestore(&events_lock, flags); > >> + > >> for (;;) { > >> prepare_to_wait(&wakeup_count_wait_queue, &wait, > >> TASK_INTERRUPTIBLE); > >> @@ -806,6 +813,7 @@ bool pm_save_wakeup_count(unsigned int count) > >> { > >> unsigned int cnt, inpr; > >> unsigned long flags; > >> + struct wakeup_source *ws; > >> > >> events_check_enabled = false; > >> spin_lock_irqsave(&events_lock, flags); > >> @@ -813,6 +821,15 @@ bool pm_save_wakeup_count(unsigned int count) > >> if (cnt == count && inpr == 0) { > >> saved_count = count; > >> events_check_enabled = true; > >> + } else { > >> + rcu_read_lock(); > >> + list_for_each_entry_rcu(ws, &wakeup_sources, entry) { > >> + if (ws->active || > >> + ktime_compare(ws->last_time, last_read_time) > 0) { > >> + ws->wakeup_count++; > >> + } > >> + } > >> + rcu_read_unlock(); > >> } > >> spin_unlock_irqrestore(&events_lock, flags); > >> return events_check_enabled; > >> > > > > -- > > I speak only for myself. > > Rafael J. Wysocki, Intel Open Source Technology Center. > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/