From: Paul Mackerras <paulus@samba.org>
To: Anton Blanchard <anton@samba.org>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] powerpc: Feature nop out reservation clear when stcx checks address
Date: Wed, 11 Aug 2010 16:41:52 +1000 [thread overview]
Message-ID: <20100811064152.GC15252@drongo> (raw)
In-Reply-To: <20100811052005.GV29316@kryten>
On Wed, Aug 11, 2010 at 03:20:05PM +1000, Anton Blanchard wrote:
> All recent POWER CPUs check the address before letting the stcx succeed
> so we can create a CPU feature and nop it out. As Ben suggested, we can
> only do this in our syscall path because there is a remote possibility
> some kernel code gets interrupted by an exception that ends up operating
> on the same cacheline.
Nice... Just one nit, and that is that I think we now need a dummy
stcx in the context switch code so there is no possibility of getting
from one user context to another with a reservation still pending from
the first context. I guess our chances of getting through schedule()
without doing any atomics, bitops or spinlocks are pretty remote, but
nevertheless it might be as well to make sure.
Paul.
next prev parent reply other threads:[~2010-08-11 6:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-11 5:20 [PATCH] powerpc: Feature nop out reservation clear when stcx checks address Anton Blanchard
2010-08-11 6:41 ` Paul Mackerras [this message]
2010-08-11 8:21 ` Benjamin Herrenschmidt
2010-08-11 11:40 ` Anton Blanchard
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