On Fri, Apr 14, 2023 at 09:53:15PM +0800, Ming Lei wrote:
On Fri, Apr 14, 2023 at 02:01:26PM +0100, Pavel Begunkov wrote:
On 4/14/23 08:53, Ming Lei wrote:
> So far io_req_complete_post() only covers DEFER_TASKRUN by completing
> request via task work when the request is completed from IOWQ.
>
> However, uring command could be completed from any context, and if io
> uring is setup with DEFER_TASKRUN, the command is required to be
> completed from current context, otherwise wait on IORING_ENTER_GETEVENTS
> can't be wakeup, and may hang forever.
fwiw, there is one legit exception, when the task is half dead
task_work will be executed by a kthread. It should be fine as it
locks the ctx down, but I can't help but wonder whether it's only
ublk_cancel_queue() affected or there are more places in ublk?
No, it isn't.
It isn't triggered on nvme-pt just because command is always done
in task context.
And we know more uring command cases are coming.
FWIW, the model I had in mind (in initial days) was this -
1) io_uring_cmd_done is a simple API, it just posts one/two results into
reuglar/big SQE
2) for anything complex completion (that requires task-work), it will
use another API io_uring_cmd_complete_in_task with the provider-specific
callback (that will call above simple API eventually)
