Re: [PATCH] PM: Acquire device locks on suspend
From: Alan Stern <stern@rowland.harvard.edu>
Date: 2008-01-05 20:08:46
On Sat, 5 Jan 2008, Rafael J. Wysocki wrote:
Greg, Andrew, The appended patch is a replacement for gregkh-driver-pm-acquire-device-locks-prior-to-suspending.patch that deadlocked suspend and hibernation on some systems. Please consider for applying.
This warning message:
quoted hunk
@@ -905,6 +915,13 @@ void device_del(struct device * dev) struct device * parent = dev->parent; struct class_interface *class_intf; + if (pm_sleep_lock()) { + dev_warn(dev, "Illegal %s during suspend\n", __FUNCTION__); + dump_stack(); + } else {
will unavoidably be triggered by this code:
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+void device_pm_destroy_suspended(struct device *dev) +{ + pr_debug("PM: Removing suspended device %s:%s\n", + dev->bus ? dev->bus->name : "No Bus", + kobject_name(&dev->kobj)); + mutex_lock(&dpm_list_mtx); + list_del_init(&dev->power.entry); + mutex_unlock(&dpm_list_mtx); + up(&dev->sem); + device_unregister(dev); +}
since the call to device_del() will occur while the pm_sleep_rwsem is still locked for writing. That's why I suggested not unregistering these devices until after everything else has been resumed and the rwsem has been dropped. Another thing to watch out for: Just in case somebody ends up calling destroy_suspended_device(dev) from within dev's own resume method, you should interchange the resume_device() and the list_move_tail() calls in dpm_resume(). Alan Stern