From: David Miller <davem@davemloft.net>
To: paulmck@linux.vnet.ibm.com
Cc: npiggin@suse.de, torvalds@linux-foundation.org, anton@samba.org,
akpm@linux-foundation.org, willy@linux.intel.com,
benh@kernel.crashing.org, paulus@samba.org,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2]: atomic_t: Remove volatile from atomic_t definition
Date: Wed, 19 May 2010 12:54:49 -0700 (PDT) [thread overview]
Message-ID: <20100519.125449.56392211.davem@davemloft.net> (raw)
In-Reply-To: <20100519150132.GJ2237@linux.vnet.ibm.com>
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date: Wed, 19 May 2010 08:01:32 -0700
> On Wed, May 19, 2010 at 11:03:27PM +1000, Nick Piggin wrote:
>> For atomic_read it shouldn't matter unless gcc is *really* bad at it.
>> Ah, for atomic_read, the required semantic is surely ACCESS_ONCE, so
>> that's where the volatile is needed? (maybe it would be clearer to
>> explicitly use ACCESS_ONCE?)
>
> Explicit use of ACCESS_ONCE() where needed makes a lot of sense to me,
> and allows better code to be generated for initialization and cleanup
> code where no other task has access to the atomic_t.
I agree and I want to see this too, but I think with the tree the size
that it is we have to work backwards at this point.
Existing behavior by default, and optimized cases get tagged by using
a new interface (atomic_read_light(), test_bit{,s}_light(), etc.)
next prev parent reply other threads:[~2010-05-19 19:54 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-17 4:33 [PATCH 1/2]: atomic_t: Cast to volatile when accessing atomic variables Anton Blanchard
2010-05-17 4:34 ` [PATCH 2/2]: atomic_t: Remove volatile from atomic_t definition Anton Blanchard
2010-05-17 8:58 ` Heiko Carstens
2010-05-17 15:01 ` Linus Torvalds
2010-05-17 20:13 ` Jamie Lokier
2010-05-17 20:20 ` Linus Torvalds
2010-05-19 13:03 ` Nick Piggin
2010-05-19 14:55 ` Linus Torvalds
2010-05-19 15:01 ` Paul E. McKenney
2010-05-19 19:54 ` David Miller [this message]
2010-05-19 22:50 ` Paul E. McKenney
2010-05-21 5:27 ` Nick Piggin
2010-05-21 5:54 ` David Miller
2010-05-21 6:06 ` Nick Piggin
2010-05-21 6:10 ` David Miller
2010-05-21 6:44 ` Eric Dumazet
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