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?
One more thing, cmds should not be setting issue_flags but only
forwarding what the core io_uring code passed, it'll get tons of
bugs in no time otherwise.
static void ublk_cancel_queue(struct ublk_queue *ubq)
{
...
io_uring_cmd_done(io->cmd, UBLK_IO_RES_ABORT, 0,
IO_URING_F_UNLOCKED);
}
Can we replace it with task_work? It should be cold, and I
assume ublk_cancel_queue() doesn't assume that all requests will
put down by the end of the function as io_uring_cmd_done()
can offload it in any case.
--
Pavel Begunkov
