Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933864AbYBUWtX (ORCPT ); Thu, 21 Feb 2008 17:49:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752904AbYBUWtL (ORCPT ); Thu, 21 Feb 2008 17:49:11 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:38936 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751632AbYBUWtJ (ORCPT ); Thu, 21 Feb 2008 17:49:09 -0500 From: "Rafael J. Wysocki" To: Alan Stern Subject: Re: [Bug 10030] Suspend doesn't work when SD card is inserted Date: Thu, 21 Feb 2008 23:47:24 +0100 User-Agent: KMail/1.9.6 (enterprise 20070904.708012) Cc: Pierre Ossman , Zdenek Kabelac , Kernel development list References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200802212347.25150.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4927 Lines: 149 On Thursday, 21 of February 2008, Alan Stern wrote: > On Thu, 21 Feb 2008, Rafael J. Wysocki wrote: > > > > > --- linux-2.6.orig/drivers/base/core.c > > > > +++ linux-2.6/drivers/base/core.c > > > > @@ -929,6 +929,11 @@ void device_del(struct device *dev) > > > > struct device *parent = dev->parent; > > > > struct class_interface *class_intf; > > > > > > > > + if (in_suspend_context()) { > > > > + get_device(dev); > > > > > > Where is this get_device() undone? Shouldn't there be an extra > > > put_device() added to unregister_dropped_devices()? > > > > No, I don't think so, because unregister_dropped_devices() calls > > device_unregister() that does the put_device() eventually. > > Ah, yes. > > > If we are called by device_unregister(), the get_device() is needed to balance > > the put_device() that will be called by device_unregister() after we return. > > > > OTOH, if we are called directly, then we need to balance the put_device() > > that will be done by device_unregister() called from > > unregister_dropped_devices(). > > > > I hope I didn't miss anything. > > Okay, that sounds right. > > > > > + device_pm_schedule_removal(dev); > > > > + return; > > > > + } > > > > device_pm_remove(dev); > > > > if (parent) > > > > klist_del(&dev->knode_parent); > > > > > > And now the change to device_destroy() isn't needed at all. > > > > No, it's not. Didn't I remove it? I thought I did. > > Oh yes, you did. > > I see a possible problem in device_resume(). My copy isn't fully > up-to-date, but it looks like you call unregister_dropped_devices() > before doing the up_write(&pm_sleep_rwsem). Won't this cause > warnings in device_del() about a suspicious caller? No, it won't, because the devices' semaphores are unlocked by unregister_dropped_devices() before calling device_unregister(). BTW, below is a simplified version of the patch, without the mutex protecting suspending_task. I'd like to push it upstream if it looks good. Please also have a look at http://bugzilla.kernel.org/show_bug.cgi?id=10030. There seems to be another issue related to us holding devices' semaphores. Namely, it looks like, when the user removes the card, a concurrent thread (from a workqueue) calls device_del() and blocks on the dev->sem held by us and then something else deadlocks with this thread. I'll be looking into this tomorrow. Thanks, Rafael --- drivers/base/core.c | 5 +++++ drivers/base/power/main.c | 9 +++++++++ drivers/base/power/power.h | 5 +++++ 3 files changed, 19 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 @@ -59,6 +59,13 @@ static DECLARE_RWSEM(pm_sleep_rwsem); int (*platform_enable_wakeup)(struct device *dev, int is_on); +static struct task_struct *suspending_task; + +bool in_suspend_context(void) +{ + return (suspending_task == current); +} + /** * device_pm_add - add a device to the list of active devices * @dev: Device to be added to the list @@ -272,6 +279,7 @@ static void dpm_resume(void) mutex_lock(&dpm_list_mtx); } mutex_unlock(&dpm_list_mtx); + suspending_task = NULL; } /** @@ -460,6 +468,7 @@ static int dpm_suspend(pm_message_t stat { int error = 0; + suspending_task = current; mutex_lock(&dpm_list_mtx); while (!list_empty(&dpm_locked)) { struct list_head *entry = dpm_locked.prev; Index: linux-2.6/drivers/base/core.c =================================================================== --- linux-2.6.orig/drivers/base/core.c +++ linux-2.6/drivers/base/core.c @@ -929,6 +929,11 @@ void device_del(struct device *dev) struct device *parent = dev->parent; struct class_interface *class_intf; + if (in_suspend_context()) { + get_device(dev); + device_pm_schedule_removal(dev); + return; + } device_pm_remove(dev); if (parent) klist_del(&dev->knode_parent); Index: linux-2.6/drivers/base/power/power.h =================================================================== --- linux-2.6.orig/drivers/base/power/power.h +++ linux-2.6/drivers/base/power/power.h @@ -11,6 +11,7 @@ static inline struct device *to_device(s return container_of(entry, struct device, power.entry); } +extern bool in_suspend_context(void); extern void device_pm_add(struct device *); extern void device_pm_remove(struct device *); extern int pm_sleep_lock(void); @@ -18,6 +19,10 @@ extern void pm_sleep_unlock(void); #else /* CONFIG_PM_SLEEP */ +static inline bool in_suspend_context(void) +{ + return false; +} static inline void device_pm_add(struct device *dev) { -- 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/