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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu, 1 Apr 2021 08:39:25 -0700
Message-ID: <CAHk-=whEObPkZBe4766DmR46-=5QTUiatWbSOaD468eTgYc1tg@mail.gmail.com>
Subject: Re: [PATCH 0/6] Allow signals for IO threads
To:     Stefan Metzmacher <metze@samba.org>
Cc:     Jens Axboe <axboe@kernel.dk>, io-uring <io-uring@vger.kernel.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Apr 1, 2021 at 7:58 AM Stefan Metzmacher <metze@samba.org> wrote:
>
> >
> > Ok, the following makes gdb happy again:
> >
> > --- a/arch/x86/kernel/process.c
> > +++ b/arch/x86/kernel/process.c
> > @@ -163,6 +163,8 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
> >         /* Kernel thread ? */
> >         if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) {
> >                 memset(childregs, 0, sizeof(struct pt_regs));
> > +               if (p->flags & PF_IO_WORKER)
> > +                       childregs->cs = current_pt_regs()->cs;
> >                 kthread_frame_init(frame, sp, arg);
> >                 return 0;
> >         }
>
> Would it be possible to fix this remaining problem before 5.12 final?

Please not that way.

But doing something like

        childregs->cs = __USER_CS;
        childregs->ss = __USER_DS;
        childregs->ds = __USER_DS;
        childregs->es = __USER_DS;

might make sense (just do it unconditionally, rather than making it
special to PF_IO_WORKER).

Does that make gdb happy too?

           Linus