Message-ID: <48AD4A0B.8020805@s5r6.in-berlin.de>
Date: Thu, 21 Aug 2008 12:57:15 +0200
From: Stefan Richter <stefanr@s5r6.in-berlin.de>
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To: Peter Zijlstra <peterz@infradead.org>
CC: jmerkey@wolfmountaingroup.com, linux-kernel@vger.kernel.org,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Nick Piggin <nickpiggin@yahoo.com.au>,
       Paul E McKenney <paulmck@linux.vnet.ibm.com>,
       David Howells <dhowells@redhat.com>
Subject: Re: [ANNOUNCE] mdb: Merkey's Linux Kernel Debugger 2.6.27-rc4	released
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Peter Zijlstra wrote:
> On Wed, 2008-08-20 at 20:50 -0600, jmerkey@wolfmountaingroup.com wrote:
> 
>>  volatiles left in the code due to the previously stated
>>  (and still present) severe breakage of the GNU compiler with SMP 
>>  shared data.  most of the barrier() functions are just plain broken
>>  and do not result in proper compiler behavior in this tree. 
> 
> Can you provide explicit detail?
> 
> By using barrier() the compiler should clobber all its memory and
> registers therefore forcing a write/reload of the variable.

I hope Jeff didn't try mere barrier()s only.  smp_wmb() and smp_rmb()
are the more relevant barrier variants for mdb, from what I remember
when I last looked at it.
-- 
Stefan Richter
-=====-==--- =--- =-=-=
http://arcgraph.de/sr/
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