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169 lines
4.6 KiB
169 lines
4.6 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/spinlock.h> |
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#include <linux/task_work.h> |
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#include <linux/tracehook.h> |
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static struct callback_head work_exited; /* all we need is ->next == NULL */ |
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/** |
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* task_work_add - ask the @task to execute @work->func() |
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* @task: the task which should run the callback |
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* @work: the callback to run |
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* @notify: how to notify the targeted task |
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* |
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* Queue @work for task_work_run() below and notify the @task if @notify |
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* is @TWA_RESUME or @TWA_SIGNAL. @TWA_SIGNAL works like signals, in that the |
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* it will interrupt the targeted task and run the task_work. @TWA_RESUME |
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* work is run only when the task exits the kernel and returns to user mode, |
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* or before entering guest mode. Fails if the @task is exiting/exited and thus |
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* it can't process this @work. Otherwise @work->func() will be called when the |
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* @task goes through one of the aforementioned transitions, or exits. |
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* |
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* If the targeted task is exiting, then an error is returned and the work item |
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* is not queued. It's up to the caller to arrange for an alternative mechanism |
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* in that case. |
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* |
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* Note: there is no ordering guarantee on works queued here. The task_work |
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* list is LIFO. |
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* |
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* RETURNS: |
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* 0 if succeeds or -ESRCH. |
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*/ |
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int task_work_add(struct task_struct *task, struct callback_head *work, |
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enum task_work_notify_mode notify) |
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{ |
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struct callback_head *head; |
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/* record the work call stack in order to print it in KASAN reports */ |
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kasan_record_aux_stack(work); |
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do { |
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head = READ_ONCE(task->task_works); |
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if (unlikely(head == &work_exited)) |
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return -ESRCH; |
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work->next = head; |
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} while (cmpxchg(&task->task_works, head, work) != head); |
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switch (notify) { |
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case TWA_NONE: |
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break; |
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case TWA_RESUME: |
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set_notify_resume(task); |
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break; |
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case TWA_SIGNAL: |
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set_notify_signal(task); |
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break; |
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default: |
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WARN_ON_ONCE(1); |
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break; |
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} |
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return 0; |
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} |
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/** |
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* task_work_cancel_match - cancel a pending work added by task_work_add() |
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* @task: the task which should execute the work |
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* @match: match function to call |
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* |
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* RETURNS: |
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* The found work or NULL if not found. |
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*/ |
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struct callback_head * |
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task_work_cancel_match(struct task_struct *task, |
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bool (*match)(struct callback_head *, void *data), |
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void *data) |
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{ |
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struct callback_head **pprev = &task->task_works; |
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struct callback_head *work; |
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unsigned long flags; |
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if (likely(!task->task_works)) |
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return NULL; |
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/* |
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* If cmpxchg() fails we continue without updating pprev. |
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* Either we raced with task_work_add() which added the |
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* new entry before this work, we will find it again. Or |
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* we raced with task_work_run(), *pprev == NULL/exited. |
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*/ |
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raw_spin_lock_irqsave(&task->pi_lock, flags); |
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while ((work = READ_ONCE(*pprev))) { |
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if (!match(work, data)) |
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pprev = &work->next; |
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else if (cmpxchg(pprev, work, work->next) == work) |
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break; |
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} |
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raw_spin_unlock_irqrestore(&task->pi_lock, flags); |
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return work; |
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} |
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static bool task_work_func_match(struct callback_head *cb, void *data) |
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{ |
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return cb->func == data; |
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} |
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/** |
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* task_work_cancel - cancel a pending work added by task_work_add() |
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* @task: the task which should execute the work |
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* @func: identifies the work to remove |
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* |
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* Find the last queued pending work with ->func == @func and remove |
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* it from queue. |
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* |
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* RETURNS: |
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* The found work or NULL if not found. |
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*/ |
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struct callback_head * |
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task_work_cancel(struct task_struct *task, task_work_func_t func) |
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{ |
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return task_work_cancel_match(task, task_work_func_match, func); |
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} |
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/** |
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* task_work_run - execute the works added by task_work_add() |
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* |
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* Flush the pending works. Should be used by the core kernel code. |
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* Called before the task returns to the user-mode or stops, or when |
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* it exits. In the latter case task_work_add() can no longer add the |
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* new work after task_work_run() returns. |
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*/ |
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void task_work_run(void) |
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{ |
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struct task_struct *task = current; |
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struct callback_head *work, *head, *next; |
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for (;;) { |
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/* |
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* work->func() can do task_work_add(), do not set |
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* work_exited unless the list is empty. |
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*/ |
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do { |
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head = NULL; |
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work = READ_ONCE(task->task_works); |
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if (!work) { |
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if (task->flags & PF_EXITING) |
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head = &work_exited; |
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else |
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break; |
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} |
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} while (cmpxchg(&task->task_works, work, head) != work); |
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if (!work) |
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break; |
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/* |
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* Synchronize with task_work_cancel(). It can not remove |
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* the first entry == work, cmpxchg(task_works) must fail. |
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* But it can remove another entry from the ->next list. |
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*/ |
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raw_spin_lock_irq(&task->pi_lock); |
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raw_spin_unlock_irq(&task->pi_lock); |
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do { |
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next = work->next; |
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work->func(work); |
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work = next; |
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cond_resched(); |
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} while (work); |
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} |
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}
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