From patchwork Mon Jul 30 01:35:47 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: NeilBrown X-Patchwork-Id: 1253201 Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork2.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork2.kernel.org (Postfix) with ESMTP id 077B1DF25A for ; Mon, 30 Jul 2012 01:36:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753861Ab2G3BgE (ORCPT ); Sun, 29 Jul 2012 21:36:04 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43462 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753699Ab2G3BgD (ORCPT ); Sun, 29 Jul 2012 21:36:03 -0400 Received: from relay2.suse.de (unknown [195.135.220.254]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx2.suse.de (Postfix) with ESMTP id 64F6C98E46; Mon, 30 Jul 2012 03:36:01 +0200 (CEST) Date: Mon, 30 Jul 2012 11:35:47 +1000 From: NeilBrown To: Alessandro Zummo Cc: rtc-linux@googlegroups.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] RTC: Avoid races between RTC alarm wakeup and suspend. Message-ID: <20120730113547.2c425ea9@notabene.brown> X-Mailer: Claws Mail 3.7.10 (GTK+ 2.24.7; x86_64-suse-linux-gnu) Mime-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org If an RTC alarm fires just as suspend is happening, it is possible for suspend to complete and the alarm to be missed. To avoid the race, we must register the event with the PM core. As the event is made visible to userspace through a thread which is only scheduled by the interrupt, we need a pm_stay_awake/pm_relax pair preventing suspend from the interrupt until the thread completes its work. Signed-off-by: NeilBrown --- This makes the pm_wakeup_event() call in cmos_interrupt unnecessary as it provides suspend protection for all RTCs that use rtc_update_irq. I think the pm_stay_awake//pm_relax is needed - just pm_wakup_event() is theoretically not sufficient. This is because there is no guarantee (that I know of) that the workqueue thread will actually get scheduled before 'suspend' takes over. Thanks, NeilBrown diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c index eb415bd..9592b93 100644 --- a/drivers/rtc/interface.c +++ b/drivers/rtc/interface.c @@ -582,6 +582,7 @@ enum hrtimer_restart rtc_pie_update_irq(struct hrtimer *timer) void rtc_update_irq(struct rtc_device *rtc, unsigned long num, unsigned long events) { + pm_stay_awake(rtc->dev.parent); schedule_work(&rtc->irqwork); } EXPORT_SYMBOL_GPL(rtc_update_irq); @@ -844,6 +845,7 @@ void rtc_timer_do_work(struct work_struct *work) mutex_lock(&rtc->ops_lock); again: + pm_relax(rtc->dev.parent); __rtc_read_time(rtc, &tm); now = rtc_tm_to_ktime(tm); while ((next = timerqueue_getnext(&rtc->timerqueue))) {