129 lines
3.4 KiB
C
129 lines
3.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
#include <linux/spinlock.h>
|
|
#include <linux/task_work.h>
|
|
#include <linux/tracehook.h>
|
|
|
|
static struct callback_head work_exited; /* all we need is ->next == NULL */
|
|
|
|
/**
|
|
* task_work_add - ask the @task to execute @work->func()
|
|
* @task: the task which should run the callback
|
|
* @work: the callback to run
|
|
* @notify: send the notification if true
|
|
*
|
|
* Queue @work for task_work_run() below and notify the @task if @notify.
|
|
* Fails if the @task is exiting/exited and thus it can't process this @work.
|
|
* Otherwise @work->func() will be called when the @task returns from kernel
|
|
* mode or exits.
|
|
*
|
|
* This is like the signal handler which runs in kernel mode, but it doesn't
|
|
* try to wake up the @task.
|
|
*
|
|
* Note: there is no ordering guarantee on works queued here.
|
|
*
|
|
* RETURNS:
|
|
* 0 if succeeds or -ESRCH.
|
|
*/
|
|
int
|
|
task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
|
|
{
|
|
struct callback_head *head;
|
|
|
|
do {
|
|
head = READ_ONCE(task->task_works);
|
|
if (unlikely(head == &work_exited))
|
|
return -ESRCH;
|
|
work->next = head;
|
|
} while (cmpxchg(&task->task_works, head, work) != head);
|
|
|
|
if (notify)
|
|
set_notify_resume(task);
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
struct callback_head **pprev = &task->task_works;
|
|
struct callback_head *work;
|
|
unsigned long flags;
|
|
|
|
if (likely(!task->task_works))
|
|
return NULL;
|
|
/*
|
|
* If cmpxchg() fails we continue without updating pprev.
|
|
* Either we raced with task_work_add() which added the
|
|
* new entry before this work, we will find it again. Or
|
|
* we raced with task_work_run(), *pprev == NULL/exited.
|
|
*/
|
|
raw_spin_lock_irqsave(&task->pi_lock, flags);
|
|
while ((work = READ_ONCE(*pprev))) {
|
|
if (work->func != func)
|
|
pprev = &work->next;
|
|
else if (cmpxchg(pprev, work, work->next) == work)
|
|
break;
|
|
}
|
|
raw_spin_unlock_irqrestore(&task->pi_lock, flags);
|
|
|
|
return work;
|
|
}
|
|
|
|
/**
|
|
* task_work_run - execute the works added by task_work_add()
|
|
*
|
|
* Flush the pending works. Should be used by the core kernel code.
|
|
* Called before the task returns to the user-mode or stops, or when
|
|
* it exits. In the latter case task_work_add() can no longer add the
|
|
* new work after task_work_run() returns.
|
|
*/
|
|
void task_work_run(void)
|
|
{
|
|
struct task_struct *task = current;
|
|
struct callback_head *work, *head, *next;
|
|
|
|
for (;;) {
|
|
/*
|
|
* work->func() can do task_work_add(), do not set
|
|
* work_exited unless the list is empty.
|
|
*/
|
|
do {
|
|
head = NULL;
|
|
work = READ_ONCE(task->task_works);
|
|
if (!work) {
|
|
if (task->flags & PF_EXITING)
|
|
head = &work_exited;
|
|
else
|
|
break;
|
|
}
|
|
} while (cmpxchg(&task->task_works, work, head) != work);
|
|
|
|
if (!work)
|
|
break;
|
|
/*
|
|
* Synchronize with task_work_cancel(). It can not remove
|
|
* the first entry == work, cmpxchg(task_works) must fail.
|
|
* But it can remove another entry from the ->next list.
|
|
*/
|
|
raw_spin_lock_irq(&task->pi_lock);
|
|
raw_spin_unlock_irq(&task->pi_lock);
|
|
|
|
do {
|
|
next = work->next;
|
|
work->func(work);
|
|
work = next;
|
|
cond_resched();
|
|
} while (work);
|
|
}
|
|
}
|