From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: David Miller <davem@davemloft.net>
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 15:50:46 -0700 [thread overview]
Message-ID: <20100519225046.GO2237@linux.vnet.ibm.com> (raw)
In-Reply-To: <20100519.125449.56392211.davem@davemloft.net>
On Wed, May 19, 2010 at 12:54:49PM -0700, David Miller wrote:
> 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.)
Fair enough!
Thanx, Paul
next prev parent reply other threads:[~2010-05-19 22:50 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
2010-05-19 22:50 ` Paul E. McKenney [this message]
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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