linux-kernel - Re: [ANNOUNCE] Merkey's Kernel Debugger

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Date:	Thu, 7 Aug 2008 09:52:53 -0600 (MDT)
From:	jmerkey@...fmountaingroup.com
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	jmerkey@...fmountaingroup.com, "Andi Kleen" <andi@...stfloor.org>,
	"Jason Wessel" <jason.wessel@...driver.com>,
	"Nick Piggin" <nickpiggin@...oo.com.au>,
	"Geert Uytterhoeven" <geert@...ux-m68k.org>,
	"Stefan Richter" <stefanr@...6.in-berlin.de>,
	"Josh Boyer" <jwboyer@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [ANNOUNCE] Merkey's Kernel Debugger

>> Also, whoever wrote "/Documentation/volatiles_are_evil" must not have
>> worked with the busted-ass GNU compiler that optimizes away global
>> variables and busts SMP dependent code.  I am not going to remove the
>
> The Linux way to handle this is to use gcc memory barriers.
> mb()/barrier()/wmb()/rmb()/smp_rmb()/smp_wmb() etc.
> Normally everything that volatile can do can be expressed by them.
>
> On x86 such a memory barrier tells gcc that memory might
> have been clobbered and needs to be flushed and also prevents the compiler
> from reordering memory accesses. On other architectures it also forces
> ordering
> on the CPU level, although that's not needed on x86 (except
> in some special situations like using write-combining)
>
> See Documentation/memory-barriers.txt
>
> -Andi
>
>

Andi,

I'll instrument this as described in the documentation you referenced and
remove the volatile declarations.  If this passes testing, I will repost
with these corections.

Jeff




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