From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 1 Dec 2011 13:26:22 +1100
From: Anton Blanchard <anton@samba.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH] powerpc/nvram: Add spinlock to oops_to_nvram to prevent
 oops in compression code.
Message-ID: <20111201132622.2b23a1d7@kryten>
In-Reply-To: <1322705472.3729.11.camel@pasglop>
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Hi Ben,

> How would we miss ?
> 
> trylock does loop on stwcx. failure, it doesn't loop if the lock is
> -taken-, so if the lock is only used for actually dealing with the
> oops the only "miss" is because somebody already got it... or am I
> missing something ?

I'm thinking of two CPUs that enter at exactly the same time either
through a system reset or an ugly bug (writing junk at 0x900 so the
decrementer exception gets an oops). Probably unlikely enough that we
don't care.

Anton