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From: Mike Frysinger <vapier.adi@gmail.com>
Date: Thu, 18 Jun 2009 20:49:02 -0400
Message-ID: <8bd0f97a0906181749h43f70338te96ea41f90caa3b7@mail.gmail.com>
Subject: Re: [PATCH 1/2] lib: Provide generic atomic64_t implementation
To: Paul Mackerras <paulus@samba.org>
Cc: benh@kernel.crashing.org, torvalds@linux-foundation.org,
       akpm@linux-foundation.org, linuxppc-dev@ozlabs.org,
       linux-kernel@vger.kernel.org
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On Thu, Jun 18, 2009 at 20:47, Paul Mackerras wrote:
> Mike Frysinger writes:
>> On Sat, Jun 13, 2009 at 03:10, Paul Mackerras wrote:
>> > +typedef struct {
>> > +       long long counter;
>> > +} atomic64_t;
>>
>> lack of volatile seems odd compared to:
>> include/linux/types.h:
>> typedef struct {
>>     volatile int counter;
>> } atomic_t;
>
> It's only accessed under a spinlock, so I don't think it needs to be
> volatile.  On UP it's accessed within local_irq_save/restore which
> should also be compiler barriers and prevent memory access reordering,
> so again volatile isn't needed.

i'm not suggesting it is needed, i'm saying it's a bit confusing.  a
simple comment above the atomic64_t type with your simple explanation
here would go a long way.
-mike
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