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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: Alan 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: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Stern 2007-05-29 16:34:52 -04:00 committed by Linus Torvalds
parent c420bc9f09
commit d5d4db704b
3 changed files with 26 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/usb/core/hcd.c
View File

@ -1681,7 +1681,7 @@ void usb_remove_hcd(struct usb_hcd *hcd)
spin_unlock_irq (&hcd_root_hub_lock); spin_unlock_irq (&hcd_root_hub_lock);
#ifdef CONFIG_PM #ifdef CONFIG_PM
flush_workqueue(ksuspend_usb_wq); cancel_work_sync(&hcd->wakeup_work);
#endif #endif
mutex_lock(&usb_bus_list_lock); mutex_lock(&usb_bus_list_lock);

32
drivers/usb/core/hub.c
View File

@ -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) * usb_disconnect - disconnect a device (usbcore-internal)
* @pdev: pointer to device being disconnected * @pdev: pointer to device being disconnected
@ -1224,13 +1248,7 @@ void usb_disconnect(struct usb_device **pdev)
*pdev = NULL; *pdev = NULL;
spin_unlock_irq(&device_state_lock); spin_unlock_irq(&device_state_lock);
/* Decrement the parent's count of unsuspended children */ usb_stop_pm(udev);
if (udev->parent) {
usb_pm_lock(udev);
if (!udev->discon_suspended)
usb_autosuspend_device(udev->parent);
usb_pm_unlock(udev);
}
put_device(&udev->dev); put_device(&udev->dev);
} }

4
drivers/usb/core/usb.c
View File

@ -184,10 +184,6 @@ static void usb_release_dev(struct device *dev)
udev = to_usb_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_destroy_configuration(udev);
usb_put_hcd(bus_to_hcd(udev->bus)); usb_put_hcd(bus_to_hcd(udev->bus));
kfree(udev->product); kfree(udev->product);