On Mon, Feb 17, 2014 at 04:18:52PM -0800, Linus Torvalds wrote:
On Mon, Feb 17, 2014 at 3:41 PM, Torvald Riegel trie...@redhat.com wrote:
There's an underlying problem here that's independent from the actual
instance that you're worried about here: no sense is a ultimately a
matter of
On Mon, Feb 17, 2014 at 12:18:21PM -0800, Linus Torvalds wrote:
On Mon, Feb 17, 2014 at 11:55 AM, Torvald Riegel trie...@redhat.com wrote:
Which example do you have in mind here? Haven't we resolved all the
debated examples, or did I miss any?
Well, Paul seems to still think that the
On Mon, Feb 17, 2014 at 07:24:56PM -0800, Linus Torvalds wrote:
On Mon, Feb 17, 2014 at 7:00 PM, Paul E. McKenney
paul...@linux.vnet.ibm.com wrote:
One example that I learned about last week uses the branch-prediction
hardware to validate value speculation. And no, I am not at all a fan
On Mon, Feb 17, 2014 at 07:42:42PM -0800, Linus Torvalds wrote:
On Mon, Feb 17, 2014 at 7:24 PM, Linus Torvalds
torva...@linux-foundation.org wrote:
As far as I can tell, the intent is that you can't do value
speculation (except perhaps for the relaxed, which quite frankly
sounds largely
On Thu, Feb 13, 2014 at 08:43:01PM -0800, Torvald Riegel wrote:
On Thu, 2014-02-13 at 18:01 -0800, Paul E. McKenney wrote:
[ . . . ]
Another option would be to flag the conditional expression, prohibiting
the compiler from optimizing out any conditional branches. Perhaps
something like
On Fri, Feb 14, 2014 at 12:02:23PM -0800, Linus Torvalds wrote:
On Fri, Feb 14, 2014 at 11:50 AM, Linus Torvalds
torva...@linux-foundation.org wrote:
Why are we still discussing this idiocy? It's irrelevant. If the
standard really allows random store speculation, the standard doesn't
On Fri, Feb 14, 2014 at 06:48:02PM -0800, Linus Torvalds wrote:
On Fri, Feb 14, 2014 at 6:44 PM, Linus Torvalds
torva...@linux-foundation.org wrote:
And conversely, the C11 people can walk away from us too. But if they
can't make us happy (and by make us happy, I really mean no stupid
On Fri, Feb 14, 2014 at 10:35:44PM -0800, Paul E. McKenney wrote:
On Fri, Feb 14, 2014 at 06:48:02PM -0800, Linus Torvalds wrote:
On Fri, Feb 14, 2014 at 6:44 PM, Linus Torvalds
torva...@linux-foundation.org wrote:
And conversely, the C11 people can walk away from us too
On Thu, Feb 13, 2014 at 12:03:57PM -0800, Torvald Riegel wrote:
On Wed, 2014-02-12 at 16:23 -0800, Paul E. McKenney wrote:
On Wed, Feb 12, 2014 at 12:22:53PM -0800, Linus Torvalds wrote:
On Wed, Feb 12, 2014 at 10:07 AM, Paul E. McKenney
paul...@linux.vnet.ibm.com wrote:
Us Linux
On Tue, Feb 11, 2014 at 10:06:34PM -0800, Torvald Riegel wrote:
On Tue, 2014-02-11 at 07:59 -0800, Paul E. McKenney wrote:
On Mon, Feb 10, 2014 at 11:09:24AM -0800, Linus Torvalds wrote:
On Sun, Feb 9, 2014 at 4:27 PM, Torvald Riegel trie...@redhat.com wrote:
Intuitively
On Wed, Feb 12, 2014 at 10:19:07AM +0100, Peter Zijlstra wrote:
I don't know the specifics of your example, but from how I understand
it, I don't see a problem if the compiler can prove that the store will
always happen.
To be more specific, if the compiler can prove that the store will
On Tue, Feb 11, 2014 at 09:39:24PM -0800, Torvald Riegel wrote:
On Mon, 2014-02-10 at 11:09 -0800, Linus Torvalds wrote:
On Sun, Feb 9, 2014 at 4:27 PM, Torvald Riegel trie...@redhat.com wrote:
Intuitively, this is wrong because this let's the program take a step
the abstract machine
On Tue, Feb 11, 2014 at 09:13:34PM -0800, Torvald Riegel wrote:
On Sun, 2014-02-09 at 19:51 -0800, Paul E. McKenney wrote:
On Mon, Feb 10, 2014 at 01:06:48AM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 20:20 -0800, Paul E. McKenney wrote:
On Fri, Feb 07, 2014 at 12:44:48AM +0100
On Wed, Feb 12, 2014 at 12:22:53PM -0800, Linus Torvalds wrote:
On Wed, Feb 12, 2014 at 10:07 AM, Paul E. McKenney
paul...@linux.vnet.ibm.com wrote:
Us Linux-kernel hackers will often need to use volatile semantics in
combination with C11 atomics in most cases. The C11 atomics do cover
On Mon, Feb 10, 2014 at 11:09:24AM -0800, Linus Torvalds wrote:
On Sun, Feb 9, 2014 at 4:27 PM, Torvald Riegel trie...@redhat.com wrote:
Intuitively, this is wrong because this let's the program take a step
the abstract machine wouldn't do. This is different to the sequential
code that
On Mon, Feb 10, 2014 at 11:49:29AM +, Will Deacon wrote:
On Mon, Feb 10, 2014 at 11:48:13AM +, Peter Zijlstra wrote:
On Fri, Feb 07, 2014 at 10:02:16AM -0800, Paul E. McKenney wrote:
As near as I can tell, compiler writers hate the idea of prohibiting
speculative-store
On Mon, Feb 10, 2014 at 01:27:51AM +0100, Torvald Riegel wrote:
On Fri, 2014-02-07 at 10:02 -0800, Paul E. McKenney wrote:
On Fri, Feb 07, 2014 at 04:55:48PM +, Will Deacon wrote:
Hi Paul,
On Fri, Feb 07, 2014 at 04:50:28PM +, Paul E. McKenney wrote:
On Fri, Feb 07, 2014
On Mon, Feb 10, 2014 at 01:27:51AM +0100, Torvald Riegel wrote:
On Fri, 2014-02-07 at 10:02 -0800, Paul E. McKenney wrote:
On Fri, Feb 07, 2014 at 04:55:48PM +, Will Deacon wrote:
[ . . . ]
And then it is a short and uncontroversial step to the following:
Initial state: x == y == 0
On Mon, Feb 10, 2014 at 01:06:48AM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 20:20 -0800, Paul E. McKenney wrote:
On Fri, Feb 07, 2014 at 12:44:48AM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 14:11 -0800, Paul E. McKenney wrote:
On Thu, Feb 06, 2014 at 10:17:03PM +0100
On Fri, Feb 07, 2014 at 10:13:40AM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 20:06 -0800, Paul E. McKenney wrote:
On Thu, Feb 06, 2014 at 11:58:22PM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 13:55 -0800, Paul E. McKenney wrote:
On Thu, Feb 06, 2014 at 10:09:25PM +0100
On Fri, Feb 07, 2014 at 12:01:25PM +, Will Deacon wrote:
Hello Torvald,
It looks like Paul clarified most of the points I was trying to make
(thanks Paul!), so I won't go back over them here.
On Thu, Feb 06, 2014 at 09:09:25PM +, Torvald Riegel wrote:
Are you familiar with the
On Fri, Feb 07, 2014 at 08:44:05AM +0100, Peter Zijlstra wrote:
On Thu, Feb 06, 2014 at 08:20:51PM -0800, Paul E. McKenney wrote:
Hopefully some discussion of out-of-thin-air values as well.
Yes, absolutely shoot store speculation in the head already. Then drive
a wooden stake through its
On Fri, Feb 07, 2014 at 04:55:48PM +, Will Deacon wrote:
Hi Paul,
On Fri, Feb 07, 2014 at 04:50:28PM +, Paul E. McKenney wrote:
On Fri, Feb 07, 2014 at 08:44:05AM +0100, Peter Zijlstra wrote:
On Thu, Feb 06, 2014 at 08:20:51PM -0800, Paul E. McKenney wrote:
Hopefully some
On Fri, Feb 07, 2014 at 05:13:36PM +, Will Deacon wrote:
On Fri, Feb 07, 2014 at 05:06:54PM +, Peter Zijlstra wrote:
On Fri, Feb 07, 2014 at 04:55:48PM +, Will Deacon wrote:
Hi Paul,
On Fri, Feb 07, 2014 at 04:50:28PM +, Paul E. McKenney wrote:
On Fri, Feb 07, 2014
On Thu, Feb 06, 2014 at 06:59:10PM +, Will Deacon wrote:
On Thu, Feb 06, 2014 at 06:55:01PM +, Ramana Radhakrishnan wrote:
On 02/06/14 18:25, David Howells wrote:
Is it worth considering a move towards using C11 atomics and barriers and
compiler intrinsics inside the kernel?
On Thu, Feb 06, 2014 at 10:09:25PM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 18:59 +, Will Deacon wrote:
On Thu, Feb 06, 2014 at 06:55:01PM +, Ramana Radhakrishnan wrote:
On 02/06/14 18:25, David Howells wrote:
Is it worth considering a move towards using C11 atomics
On Thu, Feb 06, 2014 at 10:17:03PM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 11:27 -0800, Paul E. McKenney wrote:
On Thu, Feb 06, 2014 at 06:59:10PM +, Will Deacon wrote:
On Thu, Feb 06, 2014 at 06:55:01PM +, Ramana Radhakrishnan wrote:
On 02/06/14 18:25, David Howells
On Thu, Feb 06, 2014 at 11:58:22PM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 13:55 -0800, Paul E. McKenney wrote:
On Thu, Feb 06, 2014 at 10:09:25PM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 18:59 +, Will Deacon wrote:
On Thu, Feb 06, 2014 at 06:55:01PM +
On Fri, Feb 07, 2014 at 12:44:48AM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 14:11 -0800, Paul E. McKenney wrote:
On Thu, Feb 06, 2014 at 10:17:03PM +0100, Torvald Riegel wrote:
On Thu, 2014-02-06 at 11:27 -0800, Paul E. McKenney wrote:
On Thu, Feb 06, 2014 at 06:59:10PM +
On Fri, Feb 03, 2012 at 12:00:03PM -0800, Linus Torvalds wrote:
On Fri, Feb 3, 2012 at 11:16 AM, Andrew MacLeod amacl...@redhat.com wrote:
[ . . . ]
Having access to __ATOMIC_ACQUIRE would actually be an improvement -
it's just that the architectures that really care about things like
that
On Wed, Feb 01, 2012 at 03:11:00PM -0800, Linus Torvalds wrote:
On Wed, Feb 1, 2012 at 2:45 PM, Paul E. McKenney
paul...@linux.vnet.ibm.com wrote:
My (perhaps forlorn and naive) hope is that C++11 memory_order_relaxed
will eventually allow ACCESS_ONCE() to be upgraded so that (for example
On Thu, Feb 02, 2012 at 11:08:25AM -0800, Linus Torvalds wrote:
On Thu, Feb 2, 2012 at 10:42 AM, Paul E. McKenney
paul...@linux.vnet.ibm.com wrote:
SMP-atomic or percpu atomic? Or both?
Only SMP-atomic.
And I assume that since the compiler does them, that would now make it
impossible
On Wed, Feb 01, 2012 at 12:59:24PM -0800, Linus Torvalds wrote:
On Wed, Feb 1, 2012 at 12:41 PM, Torvald Riegel trie...@redhat.com wrote:
You do rely on the compiler to do common transformations I suppose:
hoist loads out of loops, CSE, etc. How do you expect the compiler to
know whether
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