suse man page for cancel_work_sync

CANCEL_WORK_SYNC(9)						   Driver Basics					       CANCEL_WORK_SYNC(9)

NAME
       cancel_work_sync - block until a work_struct's callback has terminated

SYNOPSIS
       int cancel_work_sync(struct work_struct * work);

ARGUMENTS
       work
	   the work which is to be flushed

DESCRIPTION
       Returns true if work was pending.

       cancel_work_sync will cancel the work if it is queued. If the work's callback appears to be running, cancel_work_sync will block until it
       has completed.

       It is possible to use this function if the work re-queues itself. It can cancel the work even if it migrates to another workqueue, however
       in that case it only guarantees that work->func has completed on the last queued workqueue.

       cancel_work_sync(delayed_work->work) should be used only if ->timer is not pending, otherwise it goes into a busy-wait loop until the timer
       expires.

       The caller must ensure that workqueue_struct on which this work was last queued can't be destroyed before this function returns.

COPYRIGHT
Kernel Hackers Manual 2.6.					     July 2010						       CANCEL_WORK_SYNC(9)