From mboxrd@z Thu Jan  1 00:00:00 1970
From: Keir Fraser <keir@xensource.com>
Subject: Re: [PATCH] Fix clock_gettime to increment
	monotonically onPV-domain/x86
Date: Fri, 15 Jun 2007 11:26:35 +0100
Message-ID: <C29827EB.9300%keir@xensource.com>
References: <467283C5.76E4.0078.0@novell.com>
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To: Jan Beulich <jbeulich@novell.com>, Atsushi SAKAI <sakaia@jp.fujitsu.com>
Cc: xen-devel@lists.xensource.com
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Yeah, it needs a spinlock. Which is a shame, but it's still going to be much
faster than trapping into the hypervisor, which is the only other way we're
going to be able to achieve guaranteed monotonic time.

We could avoid the lock if we guaranteed monotonic time only per task
(thread). Or is that not really good enough? :-)

 -- Keir

On 15/6/07 11:19, "Jan Beulich" <jbeulich@novell.com> wrote:

> I'm afraid this isn't MP-safe - you're in a (pseudo-)read-locked section of
> code,
> yet write a global variable (and even in two pieces). Jan
> 
>>>> Atsushi SAKAI <sakaia@jp.fujitsu.com> 15.06.07 11:47 >>>
> Hi, Keir
> 
>   This patch intends to increment do_gettimeofday monotonically.
> This is for PV-domain/x86.
> 
> Signed-off-by: Atsushi SAKAI <sakaia@jp.fujitsu.com>
> 
> By applying patch, the time rollback for SMP is fixed.
> This is important fixes for database software.
> 
> Thanks
> Atsushi SAKAI
> 
> 
> 
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