On 23/11/2020 07:34, Hillf Danton wrote:
[...]
> After staring the report and 311daef8013a a bit more, it seems that we
> can have a simpler fix without the help of wakeup. It is implemented
> by busy waiting until there is no more request in flight found.
I think it's better not. It doesn't happen instantly, so may take a
lot of spinning in some cases. Moreover, I don't want an unkillable
task eating up all CPU if this hangs again (eg because of some other
case).
And, I'd love to keep it working similarly to __io_uring_task_cancel()
to not think twice about all corner cases.
>
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -6077,13 +6077,10 @@ static int io_req_defer(struct io_kiocb
> static void io_req_drop_files(struct io_kiocb *req)
> {
> struct io_ring_ctx *ctx = req->ctx;
> - struct io_uring_task *tctx = req->task->io_uring;
> unsigned long flags;
>
> spin_lock_irqsave(&ctx->inflight_lock, flags);
> list_del(&req->inflight_entry);
> - if (atomic_read(&tctx->in_idle))
> - wake_up(&tctx->wait);
> spin_unlock_irqrestore(&ctx->inflight_lock, flags);
> req->flags &= ~REQ_F_INFLIGHT;
> put_files_struct(req->work.identity->files);
> @@ -8706,7 +8703,6 @@ static void io_uring_cancel_files(struct
> while (!list_empty_careful(&ctx->inflight_list)) {
> struct io_task_cancel cancel = { .task = task, .files = NULL, };
> struct io_kiocb *req;
> - DEFINE_WAIT(wait);
> bool found = false;
>
> spin_lock_irq(&ctx->inflight_lock);
> @@ -8718,9 +8714,6 @@ static void io_uring_cancel_files(struct
> found = true;
> break;
> }
> - if (found)
> - prepare_to_wait(&task->io_uring->wait, &wait,
> - TASK_UNINTERRUPTIBLE);
> spin_unlock_irq(&ctx->inflight_lock);
>
> /* We need to keep going until we don't find a matching req */
> @@ -8733,7 +8726,6 @@ static void io_uring_cancel_files(struct
> /* cancellations _may_ trigger task work */
> io_run_task_work();
> schedule();
> - finish_wait(&task->io_uring->wait, &wait);
> }
> }
>
>
--
Pavel Begunkov
