linux-kernel - Re: [PATCH, RESEND] microblaze: Fix level interrupt ACKing

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Message-Id: <1258742956.2881.3.camel@iscandar.digidescorp.com>
Date:	Fri, 20 Nov 2009 12:49:16 -0600
From:	"Steven J. Magnani" <steve@...idescorp.com>
To:	monstr@...str.eu
Cc:	microblaze-uclinux@...e.uq.edu.au, linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RESEND] microblaze: Fix level interrupt ACKing

On Fri, 2009-11-20 at 12:07 +0100, Michal Simek wrote:
> Hi Steve,
> 
> steve@...idescorp.com wrote:
> > Level interrupts need to be ack'd in the unmask handler, as in powerpc. 
> > Among other issues, this bug causes the system clock to appear to run at 
> > double-speed.
> 
> Can you send me any step-by-step manual how to demonstrate me this 
> fault? If system clock runs at double-speed, then I should be able able 
> to see that time is two times faster. Or do you mean different behavior?

Unless there's a way to read jiffies_64 in userspace, the easiest way I
know of is to use the debugger. Stop the kernel soon after you boot it,
and read jiffies_64. Continue execution for some known amount of
wall-clock time, then stop the kernel again and recheck jiffies_64.
Without the patch, the number of elapsed jiffies is twice what you'd
expect based on HZ.

> 
> Thanks,
> Michal

Regards,
------------------------------------------------------------------------
 Steven J. Magnani               "I claim this network for MARS!
 www.digidescorp.com              Earthling, return my space modulator!"

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