Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753902Ab0AXUIs (ORCPT ); Sun, 24 Jan 2010 15:08:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753670Ab0AXUIr (ORCPT ); Sun, 24 Jan 2010 15:08:47 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:45150 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753649Ab0AXUIp (ORCPT ); Sun, 24 Jan 2010 15:08:45 -0500 From: "Rafael J. Wysocki" To: Alan Stern Subject: Re: [PATCH 2/8] PM: Asynchronous suspend and resume of devices Date: Sun, 24 Jan 2010 21:09:15 +0100 User-Agent: KMail/1.12.3 (Linux/2.6.33-rc4-rjw; KDE/4.3.3; x86_64; ; ) Cc: LKML , Linus Torvalds , pm list , linux-usb@vger.kernel.org, Greg KH , Arjan van de Ven , Nigel Cunningham References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201001242109.15407.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4200 Lines: 106 [CC list trimmed.] On Sunday 24 January 2010, Alan Stern wrote: > On Sun, 24 Jan 2010, Rafael J. Wysocki wrote: > > > The async threads started for different devices as a result of > > calling async_schedule() are synchronized with each other and with > > the main suspend/resume thread with the help of completions, in the > > following way: > > (1) There is a completion, power.completion, for each device object. > > (2) Each device's completion is reset before calling async_schedule() > > for the device or, in the case of devices with the > > power.async_suspend flags unset, before executing the device's > > suspend and resume callbacks. > > (3) During suspend, right before running the bus type, device type > > and device class suspend callbacks for the device, the PM core > > waits for the completions of all the device's children to be > > completed. > > (4) During resume, right before running the bus type, device type and > > device class resume callbacks for the device, the PM core waits > > for the completion of the device's parent to be completed. > > (5) The PM core completes power.completion for each device right > > after the bus type, device type and device class suspend (or > > resume) callbacks executed for the device have returned. > > ... > > > /** > > + * dpm_wait - Wait for a PM operation to complete. > > + * @dev: Device to wait for. > > + * @async: If unset, wait only if the device's power.async_suspend flag is set. > > + */ > > +static void dpm_wait(struct device *dev, bool async) > > +{ > > + if (!dev) > > + return; > > + > > + if (async || dev->power.async_suspend) > > + wait_for_completion(&dev->power.completion); > > +} > > There needs to be a public interface to this function available for > drivers that have non-tree constraints. The arguments should be the > device to wait for and the device doing the waiting (needed only to > determine whether the caller is running synchronously or not). Something like the patch below? > This will be necessary for USB. In fact, your current code (with patch > 7/8 applied) is subject to a race that will sometimes cause a > non-high-speed USB device to fail to resume from hibernation. That's the kind of information I need at this point. What exactly should be added to patch 7/8 to avoid this problem? Rafael --- drivers/base/power/main.c | 11 +++++++++++ include/linux/pm.h | 2 ++ 2 files changed, 13 insertions(+) Index: linux-2.6/drivers/base/power/main.c =================================================================== --- linux-2.6.orig/drivers/base/power/main.c +++ linux-2.6/drivers/base/power/main.c @@ -1050,3 +1050,14 @@ void __suspend_report_result(const char printk(KERN_ERR "%s(): %pF returns %d\n", function, fn, ret); } EXPORT_SYMBOL_GPL(__suspend_report_result); + +/** + * device_pm_wait_for_dev - Wait for suspend/resume of a device to complete. + * @dev: Device to wait for. + * @subordinate: Device that needs to wait for @dev. + */ +void device_pm_wait_for_dev(struct device *subordinate, struct device *dev) +{ + dpm_wait(dev, subordinate->power.async_suspend); +} +EXPORT_SYMBOL_GPL(device_pm_wait_for_dev); Index: linux-2.6/include/linux/pm.h =================================================================== --- linux-2.6.orig/include/linux/pm.h +++ linux-2.6/include/linux/pm.h @@ -512,6 +512,7 @@ extern void __suspend_report_result(cons __suspend_report_result(__func__, fn, ret); \ } while (0) +extern void device_pm_wait_for_dev(struct device *sub, struct device *dev); #else /* !CONFIG_PM_SLEEP */ #define device_pm_lock() do {} while (0) @@ -524,6 +525,7 @@ static inline int dpm_suspend_start(pm_m #define suspend_report_result(fn, ret) do {} while (0) +static inline void device_pm_wait_for_dev(struct device *a, struct device *b) {} #endif /* !CONFIG_PM_SLEEP */ /* How to reorder dpm_list after device_move() */ -- 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/