Re: [PATCH 0/2] Don't show PF_IO_WORKER in /proc/<pid>/task/

 Jens Axboe
 ` [PATCH 1/2] kernel: don't include PF_IO_WORKERs as part of same_thread_group() Jens Axboe
 ` [PATCH 2/2] proc: don't show PF_IO_WORKER threads as threads in /proc/<pid>/task/ Jens Axboe
   ` [proc] 43b2a76b1a: will-it-scale.per_process_ops -11.3% regression kernel test robot
 ` [PATCH 0/2] Don't show PF_IO_WORKER in /proc/<pid>/task/ Eric W. Biederman
   ` Linus Torvalds
     ` Jens Axboe
     ` Linus Torvalds
       ` Jens Axboe
         ` Eric W. Biederman [this message]
           ` Oleg Nesterov
             ` Jens Axboe
             ` Eric W. Biederman
           ` Jens Axboe
       ` Linus Torvalds
         ` Jens Axboe
           ` Jens Axboe
             ` Stefan Metzmacher
               ` Jens Axboe
                 ` Stefan Metzmacher
                   ` Stefan Metzmacher
             ` Linus Torvalds
               ` Jens Axboe
         ` Eric W. Biederman
           ` Jens Axboe
         ` Oleg Nesterov
           ` Eric W. Biederman
             ` Stefan Metzmacher
               ` Stefan Metzmacher
   ` Jens Axboe
     ` Oleg Nesterov

Jens Axboe <axboe@kernel.dk> writes:

> On 3/25/21 1:42 PM, Linus Torvalds wrote:
>> On Thu, Mar 25, 2021 at 12:38 PM Linus Torvalds
>> <torvalds@linux-foundation.org> wrote:
>>>
>>> I don't know what the gdb logic is, but maybe there's some other
>>> option that makes gdb not react to them?
>> 
>> .. maybe we could have a different name for them under the task/
>> subdirectory, for example (not  just the pid)? Although that probably
>> messes up 'ps' too..
>
> Heh, I can try, but my guess is that it would mess up _something_, if
> not ps/top.

Hmm.

So looking quickly the flip side of the coin is gdb (and other
debuggers) needs a way to know these threads are special, so it can know
not to attach.

I suspect getting -EPERM (or possibly a different error code) when
attempting attach is the right was to know that a thread is not
available to be debugged.

Eric