From da8bfb090c2b30af9f3879443355f7eb1d0fe10a Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Wed, 28 Mar 2012 16:13:28 -0400 Subject: USB documentation: explain lifetime rules for unlinking URBs This patch (as1534c) updates the documentation for usb_unlink_urb and related functions. It explains that the caller must prevent the URB being unlinked from getting deallocated while the unlink is taking place. Signed-off-by: Alan Stern CC: Ming Lei Signed-off-by: Greg Kroah-Hartman --- drivers/usb/core/urb.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'drivers/usb/core/urb.c') diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c index 7239a73c1b8c..cd9b3a2cd8a7 100644 --- a/drivers/usb/core/urb.c +++ b/drivers/usb/core/urb.c @@ -539,6 +539,10 @@ EXPORT_SYMBOL_GPL(usb_submit_urb); * never submitted, or it was unlinked before, or the hardware is already * finished with it), even if the completion handler has not yet run. * + * The URB must not be deallocated while this routine is running. In + * particular, when a driver calls this routine, it must insure that the + * completion handler cannot deallocate the URB. + * * Unlinking and Endpoint Queues: * * [The behaviors and guarantees described below do not apply to virtual @@ -603,6 +607,10 @@ EXPORT_SYMBOL_GPL(usb_unlink_urb); * with error -EPERM. Thus even if the URB's completion handler always * tries to resubmit, it will not succeed and the URB will become idle. * + * The URB must not be deallocated while this routine is running. In + * particular, when a driver calls this routine, it must insure that the + * completion handler cannot deallocate the URB. + * * This routine may not be used in an interrupt context (such as a bottom * half or a completion handler), or when holding a spinlock, or in other * situations where the caller can't schedule(). @@ -640,6 +648,10 @@ EXPORT_SYMBOL_GPL(usb_kill_urb); * with error -EPERM. Thus even if the URB's completion handler always * tries to resubmit, it will not succeed and the URB will become idle. * + * The URB must not be deallocated while this routine is running. In + * particular, when a driver calls this routine, it must insure that the + * completion handler cannot deallocate the URB. + * * This routine may not be used in an interrupt context (such as a bottom * half or a completion handler), or when holding a spinlock, or in other * situations where the caller can't schedule(). -- cgit v1.2.3-59-g8ed1b