linux-kernel - Re: [PATCH RESEND v4 0/4] x86: fix get_nr_restart

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Date:   Tue, 2 Feb 2021 20:23:34 +0100
From:   Oleg Nesterov <oleg@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andy Lutomirski <luto@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Jan Kratochvil <jan.kratochvil@...hat.com>,
        Pedro Alves <palves@...hat.com>, Peter Anvin <hpa@...or.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH RESEND v4 0/4] x86: fix get_nr_restart_syscall()

On 02/02, Linus Torvalds wrote:
>
> On Tue, Feb 2, 2021 at 7:56 AM Oleg Nesterov <oleg@...hat.com> wrote:
> >
> > There is the "erestartsys-trap-debugger" test in ptrace-tests suite.
> > Do you mean you want another test in tools/testing/selftests/ptrace ?
>
> No, I guess it's fine if it's caught by the ptrace test suite - we'll
> hopefully get fairly timely "guys, you broke it" reports.
>
> Is that ptrace erestartsys-trap-debugger.c test new, or has it just
> always failed? Or is the problem that it is so expected to fail that
> we wouldn't get reports of it anyway (this clearly fell off your radar
> for a long time)?

No, this test-case is very old. It used to work when this
get_nr_restart_syscall() logic was based on the test_thread_flag(TIF_IA32)
check.

Then it started to fail somewhere 2-3 years ago, and to be honest I didn't
even try to find which exactly patch broke this test. Because this logic
was always wrong anyway, even if this test-case used to work.

I sent v1 soon after this bug was reported, but every time I was too lazy,
that is why this (minor) problem is still not fixed. So, in short, this is
my fault in any case.

Oleg.