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workqueue: implement mod_delayed_work[_on]() 

Workqueue was lacking a mechanism to modify the timeout of an already
pending delayed_work.  delayed_work users have been working around
this using several methods - using an explicit timer + work item,
messing directly with delayed_work->timer, and canceling before
re-queueing, all of which are error-prone and/or ugly.

This patch implements mod_delayed_work[_on]() which behaves similarly
to mod_timer() - if the delayed_work is idle, it's queued with the
given delay; otherwise, its timeout is modified to the new value.
Zero @delay guarantees immediate execution.

v2: Updated to reflect try_to_grab_pending() changes.  Now safe to be
    called from bh context.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@redhat.com>
This commit is contained in:
Tejun Heo 2012-08-03 10:30:47 -07:00
parent bbb68dfaba
commit 8376fe22c7
2 changed files with 57 additions and 0 deletions
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4
include/linux/workqueue.h
View File

@ -390,6 +390,10 @@ extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern bool queue_delayed_work(struct workqueue_struct *wq,
struct delayed_work *work, unsigned long delay);
extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay);
extern bool mod_delayed_work(struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay);
extern void flush_workqueue(struct workqueue_struct *wq);
extern void drain_workqueue(struct workqueue_struct *wq);

53
kernel/workqueue.c
View File

@ -1413,6 +1413,59 @@ bool queue_delayed_work(struct workqueue_struct *wq,
}
EXPORT_SYMBOL_GPL(queue_delayed_work);
/**
* mod_delayed_work_on - modify delay of or queue a delayed work on specific CPU
* @cpu: CPU number to execute work on
* @wq: workqueue to use
* @dwork: work to queue
* @delay: number of jiffies to wait before queueing
*
* If @dwork is idle, equivalent to queue_delayed_work_on(); otherwise,
* modify @dwork's timer so that it expires after @delay. If @delay is
* zero, @work is guaranteed to be scheduled immediately regardless of its
* current state.
*
* Returns %false if @dwork was idle and queued, %true if @dwork was
* pending and its timer was modified.
*
* This function is safe to call from any context other than IRQ handler.
* See try_to_grab_pending() for details.
*/
bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
struct delayed_work *dwork, unsigned long delay)
{
unsigned long flags;
int ret;
do {
ret = try_to_grab_pending(&dwork->work, true, &flags);
} while (unlikely(ret == -EAGAIN));
if (likely(ret >= 0)) {
__queue_delayed_work(cpu, wq, dwork, delay);
local_irq_restore(flags);
}
/* -ENOENT from try_to_grab_pending() becomes %true */
return ret;
}
EXPORT_SYMBOL_GPL(mod_delayed_work_on);
/**
* mod_delayed_work - modify delay of or queue a delayed work
* @wq: workqueue to use
* @dwork: work to queue
* @delay: number of jiffies to wait before queueing
*
* mod_delayed_work_on() on local CPU.
*/
bool mod_delayed_work(struct workqueue_struct *wq, struct delayed_work *dwork,
unsigned long delay)
{
return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
}
EXPORT_SYMBOL_GPL(mod_delayed_work);
/**
* worker_enter_idle - enter idle state
* @worker: worker which is entering idle state