linux-kernel - handling watchdog in SMP

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Message-Id: <EA6D7331-2E0E-44D5-A286-EFD3505139BB@kernel.crashing.org>
Date:	Wed, 24 Oct 2007 13:21:37 -0500
From:	Kumar Gala <galak@...nel.crashing.org>
To:	Wim Van Sebroeck <wim@...ana.be>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: handling watchdog in SMP

I was hoping to get some ideas on how to handle the watchdog timers  
we have on some embedded PPC (booke_wdt.c) cores when we are in a SMP  
system.

The problem is since the watchdog is part of the processor core  
depending on which processor a given system call is executed at we  
might get different behavior.  It seems like we would want to mirror  
the actions to both cores (via smp_call_function).

Looking at the file ops we currently support in booke_wdt.c it seems  
like we could mirror the actions for booke_wdt_write()/booke_wdt_ping 
() to both cores and ensure when we set something like  
WDIOC_SETTIMEOUT we set the registers in both processors.

I was wondering if anyone had any other ideas or if this model seems  
to work.

- k
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