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task_work: teach task_work_add() to do signal_wake_up()
So that the target task will exit the wait_event_interruptible-like loop and call task_work_run() asap. The patch turns "bool notify" into 0,TWA_RESUME,TWA_SIGNAL enum, the new TWA_SIGNAL flag implies signal_wake_up(). However, it needs to avoid the race with recalc_sigpending(), so the patch also adds the new JOBCTL_TASK_WORK bit included in JOBCTL_PENDING_MASK. TODO: once this patch is merged we need to change all current users of task_work_add(notify = true) to use TWA_RESUME. Cc: stable@vger.kernel.org # v5.7 Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -19,6 +19,7 @@ struct task_struct;
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#define JOBCTL_TRAPPING_BIT 21 /* switching to TRACED */
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#define JOBCTL_LISTENING_BIT 22 /* ptracer is listening for events */
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#define JOBCTL_TRAP_FREEZE_BIT 23 /* trap for cgroup freezer */
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#define JOBCTL_TASK_WORK_BIT 24 /* set by TWA_SIGNAL */
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#define JOBCTL_STOP_DEQUEUED (1UL << JOBCTL_STOP_DEQUEUED_BIT)
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#define JOBCTL_STOP_PENDING (1UL << JOBCTL_STOP_PENDING_BIT)
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@ -28,9 +29,10 @@ struct task_struct;
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#define JOBCTL_TRAPPING (1UL << JOBCTL_TRAPPING_BIT)
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#define JOBCTL_LISTENING (1UL << JOBCTL_LISTENING_BIT)
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#define JOBCTL_TRAP_FREEZE (1UL << JOBCTL_TRAP_FREEZE_BIT)
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#define JOBCTL_TASK_WORK (1UL << JOBCTL_TASK_WORK_BIT)
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#define JOBCTL_TRAP_MASK (JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)
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#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)
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#define JOBCTL_PENDING_MASK (JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK | JOBCTL_TASK_WORK)
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extern bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask);
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extern void task_clear_jobctl_trapping(struct task_struct *task);
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@ -13,7 +13,10 @@ init_task_work(struct callback_head *twork, task_work_func_t func)
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twork->func = func;
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}
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int task_work_add(struct task_struct *task, struct callback_head *twork, bool);
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#define TWA_RESUME 1
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#define TWA_SIGNAL 2
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int task_work_add(struct task_struct *task, struct callback_head *twork, int);
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struct callback_head *task_work_cancel(struct task_struct *, task_work_func_t);
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void task_work_run(void);
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@ -2529,9 +2529,6 @@ bool get_signal(struct ksignal *ksig)
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struct signal_struct *signal = current->signal;
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int signr;
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if (unlikely(current->task_works))
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task_work_run();
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if (unlikely(uprobe_deny_signal()))
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return false;
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@ -2544,6 +2541,13 @@ bool get_signal(struct ksignal *ksig)
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relock:
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spin_lock_irq(&sighand->siglock);
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current->jobctl &= ~JOBCTL_TASK_WORK;
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if (unlikely(current->task_works)) {
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spin_unlock_irq(&sighand->siglock);
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task_work_run();
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goto relock;
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}
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/*
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* Every stopped thread goes here after wakeup. Check to see if
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* we should notify the parent, prepare_signal(SIGCONT) encodes
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@ -25,9 +25,10 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */
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* 0 if succeeds or -ESRCH.
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*/
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int
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task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
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task_work_add(struct task_struct *task, struct callback_head *work, int notify)
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{
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struct callback_head *head;
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unsigned long flags;
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do {
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head = READ_ONCE(task->task_works);
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@ -36,8 +37,19 @@ task_work_add(struct task_struct *task, struct callback_head *work, bool notify)
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work->next = head;
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} while (cmpxchg(&task->task_works, head, work) != head);
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if (notify)
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switch (notify) {
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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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if (lock_task_sighand(task, &flags)) {
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task->jobctl |= JOBCTL_TASK_WORK;
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signal_wake_up(task, 0);
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unlock_task_sighand(task, &flags);
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}
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break;
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}
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return 0;
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}
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