linux-kernel - Re: [PATCH] io_thread/x86: don't reset 'cs', 'ss', 'ds' and 'es' registers for io

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Date:   Tue, 25 May 2021 15:45:11 -0400
From:   Olivier Langlois <olivier@...llion01.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Stefan Metzmacher <metze@...ba.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        io-uring <io-uring@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH] io_thread/x86: don't reset 'cs', 'ss', 'ds' and 'es'
 registers for io_threads

On Tue, 2021-05-25 at 15:39 -0400, Olivier Langlois wrote:
> This notion appears to be central when creating a coredump...
> Only tasks having the same mm than the one receiving the SIGSEGV will
> be zapped...
> 
> in zap_threads():
>                 for_each_thread(g, p) {
>                         if (unlikely(!p->mm))
>                                 continue;
>                         if (unlikely(p->mm == mm)) {
>                                 lock_task_sighand(p, &flags);
>                                 nr += zap_process(p, exit_code,
>                                                         SIGNAL_GROUP_
> E
> XIT);
>                                 unlock_task_sighand(p, &flags);
>                         }
>                         break;
>                 }

without fully understanding what I am doing... I am tempted to tweak
the condition

(unlikely(p->mm == mm))

for

(unlikely(p->mm == mm || p->flags & PF_IO_WORKER))

and see if it would resolve my coredump problem...