Re: [PATCH RFC v4 12/15] io_uring/cmd: let cmds to know about dying task

[Bernd Schubert <bschubert@ddn.com>]

On 11/5/24 02:08, Pavel Begunkov wrote:
> On 11/4/24 22:15, Bernd Schubert wrote:
>> On 11/4/24 01:28, Pavel Begunkov wrote:
> ...
>>> In general if you need to change something, either stick your
>>> name, so that I know it might be a derivative, or reflect it in
>>> the commit message, e.g.
>>>
>>> Signed-off-by: initial author
>>> [Person 2: changed this and that]
>>> Signed-off-by: person 2
>>
>> Oh sorry, for sure. I totally forgot to update the commit message.
>>
>> Somehow the initial version didn't trigger. I need to double check to
> 
> "Didn't trigger" like in "kernel was still crashing"?

My initial problem was a crash in iov_iter_get_pages2() on process
kill. And when I tested your initial patch IO_URING_F_TASK_DEAD didn't
get set. Jens then asked to test with the version that I have in my
branch and that worked fine. Although in the mean time I wonder if
I made test mistake (like just fuse.ko reload instead of reboot with
new kernel). Just fixed a couple of issues in my branch (basically
ready for the next version send), will test the initial patch
again as first thing in the morning.


> 
> FWIW, the original version is how it's handled in several places
> across io_uring, and the difference is a gap for !DEFER_TASKRUN
> when a task_work is queued somewhere in between when a task is
> started going through exit() but haven't got PF_EXITING set yet.
> IOW, should be harder to hit.
> 

Does that mean that the test for PF_EXITING is racy and we cannot
entirely rely on it?


Thanks,
Bernd