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task_work: add helper for more targeted task_work canceling

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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: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-04-01 19:53:29 -06:00
parent b2e720ace2
commit c7aab1a7c5
2 changed files with 30 additions and 7 deletions
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2
include/linux/task_work.h
View file

@ -22,6 +22,8 @@ enum task_work_notify_mode {
int task_work_add(struct task_struct *task, struct callback_head *twork, int task_work_add(struct task_struct *task, struct callback_head *twork,
enum task_work_notify_mode mode); 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); struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);
void task_work_run(void); void task_work_run(void);

35
kernel/task_work.c
View file

@ -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 * @task: the task which should execute the work
* @func: identifies the work to remove * @match: match function to call
*
* Find the last queued pending work with ->func == @func and remove
* it from queue.
* *
* RETURNS: * RETURNS:
* The found work or NULL if not found. * The found work or NULL if not found.
*/ */
struct callback_head * 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 **pprev = &task->task_works;
struct callback_head *work; 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); raw_spin_lock_irqsave(&task->pi_lock, flags);
while ((work = READ_ONCE(*pprev))) { while ((work = READ_ONCE(*pprev))) {
if (work->func != func) if (!match(work, data))
pprev = &work->next; pprev = &work->next;
else if (cmpxchg(pprev, work, work->next) == work) else if (cmpxchg(pprev, work, work->next) == work)
break; break;
@ -96,6 +95,28 @@ task_work_cancel(struct task_struct *task, task_work_func_t func)
return work; 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() * task_work_run - execute the works added by task_work_add()
* *