From patchwork Fri Jul 22 21:46:28 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kevin Hilman X-Patchwork-Id: 1001132 Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) by demeter1.kernel.org (8.14.4/8.14.4) with ESMTP id p6MLkVir016699 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO) for ; Fri, 22 Jul 2011 21:46:53 GMT Received: from canuck.infradead.org ([2001:4978:20e::1]) by merlin.infradead.org with esmtps (Exim 4.76 #1 (Red Hat Linux)) id 1QkNY4-0003sp-T9; Fri, 22 Jul 2011 21:46:21 +0000 Received: from localhost ([127.0.0.1] helo=canuck.infradead.org) by canuck.infradead.org with esmtp (Exim 4.76 #1 (Red Hat Linux)) id 1QkNY4-0002Eu-Hp; Fri, 22 Jul 2011 21:46:20 +0000 Received: from na3sys009aog112.obsmtp.com ([74.125.149.207]) by canuck.infradead.org with smtps (Exim 4.76 #1 (Red Hat Linux)) id 1QkNY0-0002Eb-UT for linux-arm-kernel@lists.infradead.org; Fri, 22 Jul 2011 21:46:18 +0000 Received: from mail-pz0-f48.google.com ([209.85.210.48]) (using TLSv1) by na3sys009aob112.postini.com ([74.125.148.12]) with SMTP ID DSNKTinvpUUNTtNpZ15XSfE2yQRF4ZycrNXk@postini.com; Fri, 22 Jul 2011 14:46:16 PDT Received: by mail-pz0-f48.google.com with SMTP id 32so5029315pzk.7 for ; Fri, 22 Jul 2011 14:46:13 -0700 (PDT) Received: by 10.68.71.170 with SMTP id w10mr730137pbu.276.1311371173279; Fri, 22 Jul 2011 14:46:13 -0700 (PDT) Received: from localhost (c-24-19-7-36.hsd1.wa.comcast.net [24.19.7.36]) by mx.google.com with ESMTPS id m7sm2086966pbk.6.2011.07.22.14.46.12 (version=TLSv1/SSLv3 cipher=OTHER); Fri, 22 Jul 2011 14:46:12 -0700 (PDT) From: Kevin Hilman To: linux-pm@lists.linux-foundation.org Subject: [RFC/PATCH v2] PM / Runtime: allow _put_sync() from interrupts-disabled context Date: Fri, 22 Jul 2011 14:46:28 -0700 Message-Id: <1311371188-28879-1-git-send-email-khilman@ti.com> X-Mailer: git-send-email 1.7.6 X-CRM114-Version: 20090807-BlameThorstenAndJenny ( TRE 0.7.6 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20110722_174617_224859_2ABF71C4 X-CRM114-Status: GOOD ( 14.91 ) X-Spam-Score: -2.3 (--) X-Spam-Report: SpamAssassin version 3.3.1 on canuck.infradead.org summary: Content analysis details: (-2.3 points) pts rule name description ---- ---------------------- -------------------------------------------------- -2.3 RCVD_IN_DNSWL_MED RBL: Sender listed at http://www.dnswl.org/, medium trust [74.125.149.207 listed in list.dnswl.org] Cc: Nishanth Menon , linux-omap@vger.kernel.org, Colin Cross , linux-arm-kernel@lists.infradead.org X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Fri, 22 Jul 2011 21:46:55 +0000 (UTC) Currently the use of pm_runtime_put_sync() is not safe from interrupts-disabled context because rpm_idle() will release the spinlock and enable interrupts for the idle callbacks. This enables interrupts during a time where interrupts were expected to be disabled, and can have strange side effects on drivers that expected interrupts to be disabled. This is not a bug since the documentation clearly states that only _put_sync_suspend() is safe in IRQ-safe mode. However, pm_runtime_put_sync() could be made safe when in IRQ-safe mode by releasing the spinlock but not re-enabling interrupts, which is what this patch aims to do. Problem was found when using some buggy drivers that set pm_runtime_irq_safe() and used _put_sync() in interrupts-disabled context. The offending drivers have been fixed to use _put_sync_suspend(), But this patch is an RFC to see if it might make sense to allow using _put_sync() from interrupts-disabled context. Reported-by: Colin Cross Tested-by: Nishanth Menon Signed-off-by: Kevin Hilman --- v2: update documentation also Documentation/power/runtime_pm.txt | 10 +++++----- drivers/base/power/runtime.c | 10 ++++++++-- 2 files changed, 13 insertions(+), 7 deletions(-) diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 14dd3c6..4ce5450 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -54,11 +54,10 @@ referred to as subsystem-level callbacks in what follows. By default, the callbacks are always invoked in process context with interrupts enabled. However, subsystems can use the pm_runtime_irq_safe() helper function to tell the PM core that a device's ->runtime_suspend() and ->runtime_resume() -callbacks should be invoked in atomic context with interrupts disabled -(->runtime_idle() is still invoked the default way). This implies that these -callback routines must not block or sleep, but it also means that the -synchronous helper functions listed at the end of Section 4 can be used within -an interrupt handler or in an atomic context. +callbacks should be invoked in atomic context with interrupts disabled. +This implies that these callback routines must not block or sleep, but it also +means that the synchronous helper functions listed at the end of Section 4 can +be used within an interrupt handler or in an atomic context. The subsystem-level suspend callback is _entirely_ _responsible_ for handling the suspend of the device as appropriate, which may, but need not include @@ -483,6 +482,7 @@ pm_runtime_suspend() pm_runtime_autosuspend() pm_runtime_resume() pm_runtime_get_sync() +pm_runtime_put_sync() pm_runtime_put_sync_suspend() 5. Runtime PM Initialization, Device Probing and Removal diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c index 8dc247c..acb3f83 100644 --- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -226,11 +226,17 @@ static int rpm_idle(struct device *dev, int rpmflags) callback = NULL; if (callback) { - spin_unlock_irq(&dev->power.lock); + if (dev->power.irq_safe) + spin_unlock(&dev->power.lock); + else + spin_unlock_irq(&dev->power.lock); callback(dev); - spin_lock_irq(&dev->power.lock); + if (dev->power.irq_safe) + spin_lock(&dev->power.lock); + else + spin_lock_irq(&dev->power.lock); } dev->power.idle_notification = false;