Commit c93493b7 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'io_uring-5.8-2020-07-01' of git://git.kernel.dk/linux-block 

Pull io_uring fixes from Jens Axboe:
 "One fix in here, for a regression in 5.7 where a task is waiting in
  the kernel for a condition, but that condition won't become true until
  task_work is run. And the task_work can't be run exactly because the
  task is waiting in the kernel, so we'll never make any progress.

  One example of that is registering an eventfd and queueing io_uring
  work, and then the task goes and waits in eventfd read with the
  expectation that it'll get woken (and read an event) when the io_uring
  request completes. The io_uring request is finished through task_work,
  which won't get run while the task is looping in eventfd read"

* tag 'io_uring-5.8-2020-07-01' of git://git.kernel.dk/linux-block:
  io_uring: use signal based task_work running
  task_work: teach task_work_add() to do signal_wake_up()
parents cd77006e ce593a6c

fs/io_uring.c

+24 −8
Original line number Diff line number Diff line
@@ -4072,6 +4072,21 @@ struct io_poll_table { 
	int error;

};



static int io_req_task_work_add(struct io_kiocb *req, struct callback_head *cb,

				int notify)

{

	struct task_struct *tsk = req->task;

	int ret;



	if (req->ctx->flags & IORING_SETUP_SQPOLL)

		notify = 0;



	ret = task_work_add(tsk, cb, notify);

	if (!ret)

		wake_up_process(tsk);

	return ret;

}



static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,

			   __poll_t mask, task_work_func_t func)

{
@@ -4095,13 +4110,13 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll, 
	 * of executing it. We can't safely execute it anyway, as we may not

	 * have the needed state needed for it anyway.

	 */

	ret = task_work_add(tsk, &req->task_work, true);

	ret = io_req_task_work_add(req, &req->task_work, TWA_SIGNAL);

	if (unlikely(ret)) {

		WRITE_ONCE(poll->canceled, true);

		tsk = io_wq_get_task(req->ctx->io_wq);

		task_work_add(tsk, &req->task_work, true);

	}

		task_work_add(tsk, &req->task_work, 0);

		wake_up_process(tsk);

	}

	return 1;

}
@@ -6182,19 +6197,20 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, 
	do {

		prepare_to_wait_exclusive(&ctx->wait, &iowq.wq,

						TASK_INTERRUPTIBLE);

		/* make sure we run task_work before checking for signals */

		if (current->task_works)

			task_work_run();

		if (io_should_wake(&iowq, false))

			break;

		schedule();

		if (signal_pending(current)) {

			ret = -EINTR;

			ret = -ERESTARTSYS;

			break;

		}

		if (io_should_wake(&iowq, false))

			break;

		schedule();

	} while (1);

	finish_wait(&ctx->wait, &iowq.wq);



	restore_saved_sigmask_unless(ret == -EINTR);

	restore_saved_sigmask_unless(ret == -ERESTARTSYS);



	return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;

}

include/linux/sched/jobctl.h

+3 −1
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ struct task_struct; 
#define JOBCTL_TRAPPING_BIT	21	/* switching to TRACED */

#define JOBCTL_LISTENING_BIT	22	/* ptracer is listening for events */

#define JOBCTL_TRAP_FREEZE_BIT	23	/* trap for cgroup freezer */

#define JOBCTL_TASK_WORK_BIT	24	/* set by TWA_SIGNAL */



#define JOBCTL_STOP_DEQUEUED	(1UL << JOBCTL_STOP_DEQUEUED_BIT)

#define JOBCTL_STOP_PENDING	(1UL << JOBCTL_STOP_PENDING_BIT)
@@ -28,9 +29,10 @@ struct task_struct; 
#define JOBCTL_TRAPPING		(1UL << JOBCTL_TRAPPING_BIT)

#define JOBCTL_LISTENING	(1UL << JOBCTL_LISTENING_BIT)

#define JOBCTL_TRAP_FREEZE	(1UL << JOBCTL_TRAP_FREEZE_BIT)

#define JOBCTL_TASK_WORK	(1UL << JOBCTL_TASK_WORK_BIT)



#define JOBCTL_TRAP_MASK	(JOBCTL_TRAP_STOP | JOBCTL_TRAP_NOTIFY)

#define JOBCTL_PENDING_MASK	(JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK)

#define JOBCTL_PENDING_MASK	(JOBCTL_STOP_PENDING | JOBCTL_TRAP_MASK | JOBCTL_TASK_WORK)



extern bool task_set_jobctl_pending(struct task_struct *task, unsigned long mask);

extern void task_clear_jobctl_trapping(struct task_struct *task);

include/linux/task_work.h

+4 −1
Original line number Diff line number Diff line
@@ -13,7 +13,10 @@ init_task_work(struct callback_head *twork, task_work_func_t func) 
	twork->func = func;

}



int task_work_add(struct task_struct *task, struct callback_head *twork, bool);

#define TWA_RESUME	1

#define TWA_SIGNAL	2

int task_work_add(struct task_struct *task, struct callback_head *twork, int);



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

void task_work_run(void);

kernel/signal.c

+7 −3
Original line number Diff line number Diff line
@@ -2529,9 +2529,6 @@ bool get_signal(struct ksignal *ksig) 
	struct signal_struct *signal = current->signal;

	int signr;



	if (unlikely(current->task_works))

		task_work_run();



	if (unlikely(uprobe_deny_signal()))

		return false;
@@ -2544,6 +2541,13 @@ bool get_signal(struct ksignal *ksig) 


relock:

	spin_lock_irq(&sighand->siglock);

	current->jobctl &= ~JOBCTL_TASK_WORK;

	if (unlikely(current->task_works)) {

		spin_unlock_irq(&sighand->siglock);

		task_work_run();

		goto relock;

	}



	/*

	 * Every stopped thread goes here after wakeup. Check to see if

	 * we should notify the parent, prepare_signal(SIGCONT) encodes

kernel/task_work.c

+14 −2
Original line number Diff line number Diff line
@@ -25,9 +25,10 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */ 
 * 0 if succeeds or -ESRCH.

 */

int

task_work_add(struct task_struct *task, struct callback_head *work, bool notify)

task_work_add(struct task_struct *task, struct callback_head *work, int notify)

{

	struct callback_head *head;

	unsigned long flags;



	do {

		head = READ_ONCE(task->task_works);
@@ -36,8 +37,19 @@ task_work_add(struct task_struct *task, struct callback_head *work, bool notify) 
		work->next = head;

	} while (cmpxchg(&task->task_works, head, work) != head);



	if (notify)

	switch (notify) {

	case TWA_RESUME:

		set_notify_resume(task);

		break;

	case TWA_SIGNAL:

		if (lock_task_sighand(task, &flags)) {

			task->jobctl |= JOBCTL_TASK_WORK;

			signal_wake_up(task, 0);

			unlock_task_sighand(task, &flags);

		}

		break;

	}



	return 0;

}

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