From: Kevin Hilman <khilman@mvista.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org
Subject: 2.6.18-rt7: rollover with 32-bit cycles_t
Date: Tue, 07 Nov 2006 17:36:11 -0800 [thread overview]
Message-ID: <4551348B.6070604@mvista.com> (raw)
On ARM, I'm noticing the 'bug' message from check_critical_timing()
where two calls to get_cycles() are compared and the 2nd is assumed to
be >= the first.
This isn't properly handling the case of rollover which occurs
relatively often with fast hardware clocks and 32-bit cycle counters.
Is this really a bug? If the get_cycles() can be assumed to run between
0 and (cycles_t)~0, using the right unsigned math could get a proper
delta even in the rollover case. Is this a safe assumption?
Kevin
next reply other threads:[~2006-11-08 1:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-08 1:36 Kevin Hilman [this message]
2006-11-08 2:06 ` 2.6.18-rt7: rollover with 32-bit cycles_t john cooper
2006-11-08 19:22 ` Kevin Hilman
2006-11-09 9:14 ` Ingo Molnar
2006-11-08 3:23 ` Daniel Walker
2006-11-08 13:29 ` john cooper
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