Messages in this thread | | | Date | Sat, 5 Jan 2008 15:08:46 -0500 (EST) | From | Alan Stern <> | Subject | Re: [PATCH] PM: Acquire device locks on suspend |
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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:
> @@ -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:
> +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
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