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From: Andrew Lutomirski <luto@mit.edu>
Date: Fri, 27 May 2011 11:05:51 -0400
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Subject: Re: [GIT pull] x86 vdso updates
To: richard -rw- weinberger <richard.weinberger@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>, x86@kernel.org,
        LKML <linux-kernel@vger.kernel.org>
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On Fri, May 27, 2011 at 10:59 AM, richard -rw- weinberger
<richard.weinberger@gmail.com> wrote:
> On Fri, May 27, 2011 at 2:10 PM, Andrew Lutomirski <luto@mit.edu> wrote:
>> On Fri, May 27, 2011 at 7:59 AM, richard -rw- weinberger
>> If this is considered enough of a regression, then I guess we can
>> leave vsyscall64 around for awhile, but it will require extra work in
>> the soon-to-be syscall emulation hack to make sure that UML can still
>> trap the syscall.
>
> As long the time within UML is synchronous with the host everything is
> fine, right?

I think so.  I haven't used UML in a long time.

> So, as _last_ choice we could disable the ability to change the time within UML.
>
> IMHO it's not a big deal when getcpu() returns a wrong CPU layout on UML.
>
>> The real solution is to fix glibc to use the vDSO which should avoid
>> this problem entirely.
>
> Is this "bug" known? And the biggest question, will Ulrich fix it some day?

I added the bit about UML to
http://sourceware.org/bugzilla/show_bug.cgi?id=12813.  I don't know
what Ulrich will do.

--Andy