Re: [PATCH] fcntl: make F_GETOWN(EX) return 0 on dead owner task

Cyrill Gorcunov
2021-02-03T22:18:12Z

On Thu, Feb 04, 2021 at 12:35:42AM +0300, Pavel Tikhomirov wrote:
>
> AFAICS if pid is held only by 1) fowner refcount and by 2) single process
> (without threads, group and session for simplicity), on process exit we go
> through:
>
> do_exit
> exit_notify
> release_task
> __exit_signal
> __unhash_process
> detach_pid
> __change_pid
> free_pid
> idr_remove
>
> So pid is removed from idr, and after that alloc_pid can reuse pid numbers
> even if old pid structure is still alive and is still held by fowner.
...
> Hope this answers your question, Thanks!

Yeah, indeed, thanks! So the change is sane still I'm
a bit worried about backward compatibility, gimme some
time I'll try to refresh my memory first, in a couple
of days or weekend (though here are a number of experienced
developers CC'ed maybe they reply even faster).