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io_uring: use io-wq manager as backup task if task is exiting

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If the original task is (or has) exited, then the task work will not get
queued properly. Allow for using the io-wq manager task to queue this
work for execution, and ensure that the io-wq manager notices and runs
this work if woken up (or exiting).

Reported-by: Dan Melnic <dmm@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2020-04-03 11:26:26 -06:00
parent 3537b6a7c6
commit aa96bf8a9e
3 changed files with 23 additions and 4 deletions
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13
fs/io_uring.c
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@@ -4120,6 +4120,7 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
__poll_t mask, task_work_func_t func)
{
struct task_struct *tsk;
int ret;
/* for instances that support it check for an event match first: */
if (mask && !(mask & poll->events))
@@ -4133,11 +4134,15 @@ static int __io_async_wake(struct io_kiocb *req, struct io_poll_iocb *poll,
req->result = mask;
init_task_work(&req->task_work, func);
/*
* If this fails, then the task is exiting. If that is the case, then
* the exit check will ultimately cancel these work items. Hence we
* don't need to check here and handle it specifically.
* If this fails, then the task is exiting. Punt to one of the io-wq
* threads to ensure the work gets run, we can't always rely on exit
* cancelation taking care of this.
*/
task_work_add(tsk, &req->task_work, true);
ret = task_work_add(tsk, &req->task_work, true);
if (unlikely(ret)) {
tsk = io_wq_get_task(req->ctx->io_wq);
task_work_add(tsk, &req->task_work, true);
}
wake_up_process(tsk);
return 1;
}