From: gilles.chanteperdrix@xenomai.org (Gilles Chanteperdrix)
To: linux-arm-kernel@lists.infradead.org
Subject: udelay() broken for SMP cores?
Date: Wed, 21 Apr 2010 11:58:34 +0200 [thread overview]
Message-ID: <4BCECC4A.7090504@xenomai.org> (raw)
In-Reply-To: <20100421095036.GA13971@n2100.arm.linux.org.uk>
Russell King - ARM Linux wrote:
> On Wed, Apr 21, 2010 at 02:39:39AM -0700, skannan at codeaurora.org wrote:
>> Is this an ARM specific decision? Cpufreq certainly supports per cpu scaling
>> and x86 udelay uses per-CPU data. So your concern should apply for x86
>> too. I had the same concern and was planning on bring it up in the cpufreq
>> mailing list after I made sure I didn't misunderstand anything.
>
> Well, x86 looks buggy in this regard as well - the loops_per_jiffy
> value used is for a CPU which may not run the delay loop.
It looks to me like x86 with a tsc use the tsc for udelay, and handle
cpu changes correctly. See the function delay_tsc in
arch/x86/lib/delay.c. However, they do not seem to handle frequency
changes that well.
--
Gilles.
next prev parent reply other threads:[~2010-04-21 9:58 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-21 2:19 udelay() broken for SMP cores? Saravana Kannan
2010-04-21 4:56 ` Shilimkar, Santosh
2010-04-21 6:43 ` Saravana Kannan
2010-04-21 7:22 ` Russell King - ARM Linux
2010-04-21 9:39 ` skannan at codeaurora.org
2010-04-21 9:50 ` Russell King - ARM Linux
2010-04-21 9:58 ` Gilles Chanteperdrix [this message]
2010-04-21 10:00 ` Jamie Lokier
2010-04-21 19:29 ` Russell King - ARM Linux
2010-04-21 19:52 ` Jamie Lokier
2010-04-21 20:21 ` Russell King - ARM Linux
2010-04-21 20:47 ` Jamie Lokier
2010-04-21 20:57 ` Russell King - ARM Linux
2010-04-22 0:14 ` Jamie Lokier
2011-01-08 23:24 ` Russell King - ARM Linux
2010-04-21 10:31 ` skannan at codeaurora.org
2010-04-21 19:33 ` Russell King - ARM Linux
2010-04-21 23:47 ` Saravana Kannan
2010-04-21 23:47 ` Saravana Kannan
2010-04-23 9:00 ` Pavel Machek
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