Commit c7aab1a7 authored by Jens Axboe's avatar Jens Axboe
Browse files

task_work: add helper for more targeted task_work canceling 



The only exported helper we have right now is task_work_cancel(), which
cancels any task_work from a given task where func matches the queued
work item. This is a bit too coarse for some use cases. Add a
task_work_cancel_match() that allows to more specifically target
individual work items outside of purely the callback function used.

task_work_cancel() can be trivially implemented on top of that, hence do
so.

Reviewed-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b2e720ac

include/linux/task_work.h

+2 −0
Original line number Diff line number Diff line
@@ -22,6 +22,8 @@ enum task_work_notify_mode { 
int task_work_add(struct task_struct *task, struct callback_head *twork,

			enum task_work_notify_mode mode);



struct callback_head *task_work_cancel_match(struct task_struct *task,

	bool (*match)(struct callback_head *, void *data), void *data);

struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);

void task_work_run(void);

kernel/task_work.c

+28 −7
Original line number Diff line number Diff line
@@ -59,18 +59,17 @@ int task_work_add(struct task_struct *task, struct callback_head *work, 
}



/**

 * task_work_cancel - cancel a pending work added by task_work_add()

 * task_work_cancel_match - cancel a pending work added by task_work_add()

 * @task: the task which should execute the work

 * @func: identifies the work to remove

 *

 * Find the last queued pending work with ->func == @func and remove

 * it from queue.

 * @match: match function to call

 *

 * RETURNS:

 * The found work or NULL if not found.

 */

struct callback_head *

task_work_cancel(struct task_struct *task, task_work_func_t func)

task_work_cancel_match(struct task_struct *task,

		       bool (*match)(struct callback_head *, void *data),

		       void *data)

{

	struct callback_head **pprev = &task->task_works;

	struct callback_head *work;
@@ -86,7 +85,7 @@ task_work_cancel(struct task_struct *task, task_work_func_t func) 
	 */

	raw_spin_lock_irqsave(&task->pi_lock, flags);

	while ((work = READ_ONCE(*pprev))) {

		if (work->func != func)

		if (!match(work, data))

			pprev = &work->next;

		else if (cmpxchg(pprev, work, work->next) == work)

			break;
@@ -96,6 +95,28 @@ task_work_cancel(struct task_struct *task, task_work_func_t func) 
	return work;

}



static bool task_work_func_match(struct callback_head *cb, void *data)

{

	return cb->func == data;

}



/**

 * task_work_cancel - cancel a pending work added by task_work_add()

 * @task: the task which should execute the work

 * @func: identifies the work to remove

 *

 * Find the last queued pending work with ->func == @func and remove

 * it from queue.

 *

 * RETURNS:

 * The found work or NULL if not found.

 */

struct callback_head *

task_work_cancel(struct task_struct *task, task_work_func_t func)

{

	return task_work_cancel_match(task, task_work_func_match, func);

}



/**

 * task_work_run - execute the works added by task_work_add()

 *