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workqueue: reimplement cancel_delayed_work() using try_to_grab_pending() 

cancel_delayed_work() can't be called from IRQ handlers due to its use
of del_timer_sync() and can't cancel work items which are already
transferred from timer to worklist.

Also, unlike other flush and cancel functions, a canceled delayed_work
would still point to the last associated cpu_workqueue.  If the
workqueue is destroyed afterwards and the work item is re-used on a
different workqueue, the queueing code can oops trying to dereference
already freed cpu_workqueue.

This patch reimplements cancel_delayed_work() using
try_to_grab_pending() and set_work_cpu_and_clear_pending().  This
allows the function to be called from IRQ handlers and makes its
behavior consistent with other flush / cancel functions.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Tejun Heo 2012-08-21 13:18:24 -07:00
parent e7c2f96744
commit 57b30ae77b
2 changed files with 31 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
include/linux/workqueue.h
View File

@ -420,6 +420,7 @@ extern bool flush_work(struct work_struct *work);
extern bool cancel_work_sync(struct work_struct *work);
extern bool flush_delayed_work(struct delayed_work *dwork);
extern bool cancel_delayed_work(struct delayed_work *dwork);
extern bool cancel_delayed_work_sync(struct delayed_work *dwork);
extern void workqueue_set_max_active(struct workqueue_struct *wq,
@ -428,22 +429,6 @@ extern bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq);
extern unsigned int work_cpu(struct work_struct *work);
extern unsigned int work_busy(struct work_struct *work);
/*
* Kill off a pending schedule_delayed_work(). Note that the work callback
* function may still be running on return from cancel_delayed_work(), unless
* it returns 1 and the work doesn't re-arm itself. Run flush_workqueue() or
* cancel_work_sync() to wait on it.
*/
static inline bool cancel_delayed_work(struct delayed_work *work)
{
bool ret;
ret = del_timer_sync(&work->timer);
if (ret)
work_clear_pending(&work->work);
return ret;
}
/*
* Like above, but uses del_timer() instead of del_timer_sync(). This means,
* if it returns 0 the timer function may be running and the queueing is in

30
kernel/workqueue.c
View File

@ -2948,6 +2948,36 @@ bool flush_delayed_work(struct delayed_work *dwork)
}
EXPORT_SYMBOL(flush_delayed_work);
/**
* cancel_delayed_work - cancel a delayed work
* @dwork: delayed_work to cancel
*
* Kill off a pending delayed_work. Returns %true if @dwork was pending
* and canceled; %false if wasn't pending. Note that the work callback
* function may still be running on return, unless it returns %true and the
* work doesn't re-arm itself. Explicitly flush or use
* cancel_delayed_work_sync() to wait on it.
*
* This function is safe to call from any context including IRQ handler.
*/
bool cancel_delayed_work(struct delayed_work *dwork)
{
unsigned long flags;
int ret;
do {
ret = try_to_grab_pending(&dwork->work, true, &flags);
} while (unlikely(ret == -EAGAIN));
if (unlikely(ret < 0))
return false;
set_work_cpu_and_clear_pending(&dwork->work, work_cpu(&dwork->work));
local_irq_restore(flags);
return true;
}
EXPORT_SYMBOL(cancel_delayed_work);
/**
* cancel_delayed_work_sync - cancel a delayed work and wait for it to finish
* @dwork: the delayed work cancel