Messages in this thread | | | From | Pavel Begunkov <> | Subject | Re: [PATCH 1/2 v2] io_uring: Fix race condition when sqp thread goes to sleep | Date | Tue, 22 Jun 2021 21:45:00 +0100 |
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On 6/22/21 7:55 PM, Olivier Langlois wrote: > If an asynchronous completion happens before the task is preparing > itself to wait and set its state to TASK_INTERRUPTIBLE, the completion > will not wake up the sqp thread. > > Signed-off-by: Olivier Langlois <olivier@trillion01.com> > --- > fs/io_uring.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/io_uring.c b/fs/io_uring.c > index fc8637f591a6..02f789e07d4c 100644 > --- a/fs/io_uring.c > +++ b/fs/io_uring.c > @@ -6902,7 +6902,7 @@ static int io_sq_thread(void *data) > } > > prepare_to_wait(&sqd->wait, &wait, TASK_INTERRUPTIBLE); > - if (!io_sqd_events_pending(sqd)) { > + if (!io_sqd_events_pending(sqd) && !current->task_works) {
Agree that it should be here, but we also lack a good enough task_work_run() around, and that may send the task burn CPU for a while in some cases. Let's do
if (!io_sqd_events_pending(sqd) && !io_run_task_work()) ...
fwiw, no need to worry about TASK_INTERRUPTIBLE as io_run_task_work() sets it to TASK_RUNNING.
> needs_sched = true; > list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) { > io_ring_set_wakeup_flag(ctx); >
-- Pavel Begunkov
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