From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH -v4 1/2] lib, Make gen_pool memory allocator lockless
Date: Wed, 17 Nov 2010 12:38:56 +0100
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To: huang ying <huang.ying.caritas@gmail.com>
Cc: Huang Ying <ying.huang@intel.com>, Andrew Morton <akpm@linux-foundation.org>, Len Brown <lenb@kernel.org>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, Andi Kleen <andi@firstfloor.org>, "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>, Mauro Carvalho Chehab <mchehab@redhat.com>, Steven Rostedt <rostedt@goodmis.org>

On Wed, 2010-11-17 at 19:16 +0800, huang ying wrote:
> > I'm not sure Andrew's CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG makes much sense
> > for CONFIG_ARCH_HAVE_NMI=n though..
> 
> Sorry, I do not find ARCH_HAVE_NMI in any Kconfig, can you help me to
> point out? I think cmpxchg can be used safely in lock-less code on
> architectures without NMI. 

It doesn't exist, but what I'm saying is that HAVE_NMI_SAFE_CMPXCHG is
pointless for architectures that don't actually have an NMI, although I
guess you can argue that since it doesn't have one its safe by default,
still slightly confusing.

Some arch don't currently implement NMI like functionality (ARM comes to
mind) but they could using interrupt priorities (like SPARC64 does for
example).