Commit d5d4db70 authored by Alan Stern's avatar Alan Stern Committed by Linus Torvalds
Browse files

USB: replace flush_workqueue with cancel_sync_work 



This patch (as912) replaces a couple of calls to flush_workqueue()
with cancel_sync_work() and cancel_rearming_delayed_work().  Using a
more directed approach allows us to avoid some nasty deadlocks.  The
prime example occurs when a first-level device (the parent is a root
hub) is removed while at the same time the root hub gets a remote
wakeup request.  khubd would try to flush the autosuspend workqueue
while holding the root-hub's lock, and the remote-wakeup workqueue
routine would be waiting to lock the root hub.

The patch also reorganizes the power management portion of
usb_disconnect(), separating it out into its own routine.  The
autosuspend workqueue entry is cancelled immediately instead of
waiting for the device's release routine.  In addition,
synchronization with the autosuspend thread is carried out even for
root hubs (an oversight in the original code).

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg KH <gregkh@suse.de>
Cc: Mark Lord <lkml@rtr.ca>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c420bc9f

drivers/usb/core/hcd.c

+1 −1
Original line number Diff line number Diff line
@@ -1681,7 +1681,7 @@ void usb_remove_hcd(struct usb_hcd *hcd) 
	spin_unlock_irq (&hcd_root_hub_lock);



#ifdef CONFIG_PM

	flush_workqueue(ksuspend_usb_wq);

	cancel_work_sync(&hcd->wakeup_work);

#endif



	mutex_lock(&usb_bus_list_lock);

drivers/usb/core/hub.c

+25 −7
Original line number Diff line number Diff line
@@ -1158,6 +1158,30 @@ static void release_address(struct usb_device *udev) 
	}

}



#ifdef	CONFIG_USB_SUSPEND



static void usb_stop_pm(struct usb_device *udev)

{

	/* Synchronize with the ksuspend thread to prevent any more

	 * autosuspend requests from being submitted, and decrement

	 * the parent's count of unsuspended children.

	 */

	usb_pm_lock(udev);

	if (udev->parent && !udev->discon_suspended)

		usb_autosuspend_device(udev->parent);

	usb_pm_unlock(udev);



	/* Stop any autosuspend requests already submitted */

	cancel_rearming_delayed_work(&udev->autosuspend);

}



#else



static inline void usb_stop_pm(struct usb_device *udev)

{ }



#endif



/**

 * usb_disconnect - disconnect a device (usbcore-internal)

 * @pdev: pointer to device being disconnected
@@ -1224,13 +1248,7 @@ void usb_disconnect(struct usb_device **pdev) 
	*pdev = NULL;

	spin_unlock_irq(&device_state_lock);



	/* Decrement the parent's count of unsuspended children */

	if (udev->parent) {

		usb_pm_lock(udev);

		if (!udev->discon_suspended)

			usb_autosuspend_device(udev->parent);

		usb_pm_unlock(udev);

	}

	usb_stop_pm(udev);



	put_device(&udev->dev);

}

drivers/usb/core/usb.c

+0 −4
Original line number Diff line number Diff line
@@ -184,10 +184,6 @@ static void usb_release_dev(struct device *dev) 


	udev = to_usb_device(dev);



#ifdef	CONFIG_USB_SUSPEND

	cancel_delayed_work(&udev->autosuspend);

	flush_workqueue(ksuspend_usb_wq);

#endif

	usb_destroy_configuration(udev);

	usb_put_hcd(bus_to_hcd(udev->bus));

	kfree(udev->product);

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