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

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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()
This commit is contained in:
Linus Torvalds
2020-07-02 14:56:22 -07:00
parent cd77006e01 ce593a6c48
commit c93493b7cd
5 changed files with 52 additions and 15 deletions
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32
fs/io_uring.c
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@@ -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);
}
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 (signal_pending(current)) {
ret = -ERESTARTSYS;
break;
}
if (io_should_wake(&iowq, false))
break;
schedule();
if (signal_pending(current)) {
ret = -EINTR;
break;
}
} 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;
}