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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Wed, 29 Apr 2020 19:20:22 -0700
Message-ID: <CAHk-=wg6oKSLkVhY5oqOFyzCCSr9eYPGK2SHJfgCXF_QOmPKog@mail.gmail.com>
Subject: Re: [GIT PULL] Please pull proc and exec work for 5.7-rc1
To:     Bernd Edlinger <bernd.edlinger@hotmail.de>
Cc:     Jann Horn <jannh@google.com>, Oleg Nesterov <oleg@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Waiman Long <longman@redhat.com>,
        Ingo Molnar <mingo@kernel.org>, Will Deacon <will@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alexey Gladkov <gladkov.alexey@gmail.com>
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On Wed, Apr 29, 2020 at 6:08 PM Bernd Edlinger
<bernd.edlinger@hotmail.de> wrote:
>
> I added the BIG FAT WARNNIG comments as a mitigation for that.
> Did you like those comments?

No.

What's the point olf saying "THIS CODE IS GARBAGE" and then expecting
that to make it ok?

No,m that doesn't make it ok. It just means that it should have been
done differently.

> Yes, exactly, the point is the caller is expected to call wait in that
> scenario, otherwise the -EAGAIN just repeats forever, that is an API
> change, yes, but something unavoidable, and the patch tries hard to
> limit it to cases where the live-lock or pseudo-dead-lock is unavoidable
> anyway.

I'm getting really fed up with your insistence on that KNOWN BROKEN
garbage test-case.

It's shit. The test-case is wrong. I've told you before.

Your patch as-is breaks other cases that are *not* wrong in the kernel
currently, and that don't have test-cases because they JustWork(tm).

The livelock isn't interesting. The test-case that shows it is pure
garbage, and is written wrong.

IF that test-case hadn't been buggy in the first place, it would have
had ignored its child (or had a handler for SIGCHLD), and not
livelocked.

                Linus