From: David Howells <dhowells@redhat.com>
To: Nicolas Pitre <nico@cam.org>
Cc: dhowells@redhat.com, Peter Zijlstra <a.p.zijlstra@chello.nl>,
torvalds@osdl.org, akpm@linux-foundation.org,
linux-am33-list@redhat.com, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/2] MN10300: Move asm-arm/cnt32_to_63.h to include/linux/
Date: Mon, 06 Oct 2008 11:44:22 +0100 [thread overview]
Message-ID: <19168.1223289862@redhat.com> (raw)
In-Reply-To: <alpine.LFD.2.00.0810031512420.3045@xanadu.home>
Nicolas Pitre <nico@cam.org> wrote:
> If so then you're using this interface in an inappropriate way.
>
> The _absolute_ minimum frequency with which this should be fully
> executed is once per half period of the base counter. I hope that in
> practice it happens far more often than that.
I think you're misunderstanding my contention.
If preemption is enabled, cnt32_to_63() can be called with greater than
minimum frequency and yet reversions can still happen.
The problem is that a process that's half way through executing cnt32_to_63()
can be preempted for a period of time sufficient that when it is rescheduled
and writes __m_cnt_hi, it corrupts it with an out of date value.
David
next prev parent reply other threads:[~2008-10-06 10:44 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-24 16:48 [PATCH 1/2] MN10300: Move asm-arm/cnt32_to_63.h to include/linux/ David Howells
2008-09-24 16:48 ` [PATCH 2/2] MN10300: Make sched_clock() report time since boot David Howells
2008-09-26 10:58 ` Peter Zijlstra
2008-09-26 10:56 ` [PATCH 1/2] MN10300: Move asm-arm/cnt32_to_63.h to include/linux/ Peter Zijlstra
2008-09-26 12:03 ` Nicolas Pitre
2008-09-26 12:08 ` Peter Zijlstra
2008-09-29 1:21 ` Nicolas Pitre
2008-09-26 12:20 ` Peter Zijlstra
2008-09-29 1:42 ` Nicolas Pitre
2008-10-01 14:34 ` David Howells
2008-10-01 15:36 ` Nicolas Pitre
2008-10-02 22:23 ` David Howells
2008-10-03 19:15 ` Nicolas Pitre
2008-10-06 10:44 ` David Howells [this message]
2008-10-06 15:06 ` Nicolas Pitre
2008-09-26 13:27 ` David Howells
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