Re: [PATCH 3/3] io_uring: refactor io_sq_offload_create()

[Jens Axboe <axboe@kernel.dk>]

On 7/22/21 6:10 PM, Al Viro wrote:
> On Thu, Jul 22, 2021 at 05:42:55PM -0600, Jens Axboe wrote:
> 
>>> So how can we possibly get there with tsk->files == NULL and what does it
>>> have to do with files, anyway?
>>
>> It's not the clearest, but the files check is just to distinguish between
>> exec vs normal cancel. For exec, we pass in files == NULL. It's not
>> related to task->files being NULL or not, we explicitly pass NULL for
>> exec.
> 
> Er...  So turn that argument into bool cancel_all, and pass false on exit and
> true on exec? 

Yes

> While we are at it, what happens if you pass io_uring descriptor
> to another process, close yours and then have the recepient close the one it
> has gotten?  AFAICS, io_ring_ctx_wait_and_kill(ctx) will be called in context
> of a process that has never done anything io_uring-related.  Can it end up
> trying to resubmit some requests?> 
> I rather hope it can't happen, but I don't see what would prevent it...

No, the pending request would either have gone to a created thread of
the original task on submission, or it would be sitting in a
ready-to-retry state. The retry would attempt to queue to original task,
and either succeed (if still alive) or get failed with -ECANCELED. Any
given request is tied to the original task.

-- 
Jens Axboe