linux-kernel - Re: [PATCH v2 20/20] signal: Don't restart fork when signals come in.

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Date:   Tue, 24 Jul 2018 13:56:05 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Wen Yang <wen.yang99@....com.cn>, majiang <ma.jiang@....com.cn>
Subject: Re: [PATCH v2 20/20] signal: Don't restart fork when signals come in.

On Tue, Jul 24, 2018 at 1:40 PM Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
> +       if (signal_pending(current)) {
> +               retval = restart_syscall();
> +               goto fork_out;
> +       }

Oh, the previous version had this too, but it wasn't as obvious
because it was just in a single line:

        return ERR_PTR(restart_syscall());

but it's just crazy.

It should just be

        retval = -ERESTARTNOINTR;
        if (signal_pending(current))
                goto fork_out;

because it's just silly and pointless to change the code to use
restart_syscall() here.

All restart_syscall() does is

        set_tsk_thread_flag(current, TIF_SIGPENDING);
        return -ERESTARTNOINTR;

and you just *checked* that TIF_SIGPENDING was already set. So the
above is completely pointless.

It is not clear why you made that change. The old code had the simpler
"just return -ERESTARTNOINTR" model.

Did the restart_syscall() thing come in by mistake from some previous
trials and it just hung around?

            Linus