linux-kernel - Re: Please review arch/x86/kernel/pvclock.c to fix Docker/Mono crashes in new Kernels

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Message-ID: <CA+55aFx+qKm8iOK+b_KoPPUvtP42XrkFD8pH4MWuiY6vkXvBxg@mail.gmail.com>
Date:	Mon, 16 May 2016 11:56:32 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	okhalzov@...m.vestbery.com, Marcelo Tosatti <mtosatti@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	"the arch/x86 maintainers" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Please review arch/x86/kernel/pvclock.c to fix Docker/Mono
 crashes in new Kernels

On Mon, May 16, 2016 at 11:37 AM, Andy Lutomirski <luto@...capital.net> wrote:
>
> All of those fixes were intended to fix incorrect times being
> reported, not segfaults.  Weird.

I'm assuming it's "time going backwards". I can easily see that
causing segfaults.

I've seen lots of code that timestamps events, and can easily imagine
confusion if the end result is not ordered (ie walking off the
beginning/end of a list or array or similar because the algorithm
"knows" that the events are ordered).

I agree that the original bisection result is a bit questionable, and
it might just be about exposing a timing issue.

                   Linus