Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-24 Thread Akira Yokosawa
On 2017/07/24 14:34:07 +0800, Boqun Feng wrote: > On Mon, Jul 24, 2017 at 09:04:57AM +0900, Akira Yokosawa wrote: > [...] >>> >>> ->8 >>> Subject: [PATCH] kernel: Emphasize the return value of READ_ONCE() is >>> honored >>> >>> READ_ONCE() is used around in kernel to provide a cont

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-23 Thread Boqun Feng
On Mon, Jul 24, 2017 at 09:04:57AM +0900, Akira Yokosawa wrote: [...] > > > > ->8 > > Subject: [PATCH] kernel: Emphasize the return value of READ_ONCE() is > > honored > > > > READ_ONCE() is used around in kernel to provide a control dependency, > > and to make the control depend

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-23 Thread Paul E. McKenney
On Mon, Jul 24, 2017 at 09:04:57AM +0900, Akira Yokosawa wrote: > On 2017/07/23 23:39:36 +0800, Boqun Feng wrote: > > On Sat, Jul 22, 2017 at 09:43:00PM -0700, Paul E. McKenney wrote: > > [...] > >>> Your priority seemed to be in reducing the chance of the "if" statement > >>> to be optimized away.

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-23 Thread Akira Yokosawa
On 2017/07/23 23:39:36 +0800, Boqun Feng wrote: > On Sat, Jul 22, 2017 at 09:43:00PM -0700, Paul E. McKenney wrote: > [...] >>> Your priority seemed to be in reducing the chance of the "if" statement >>> to be optimized away. So I suggested to use "extern" as a compromise. >> > > Hi Akira, > Hi

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-23 Thread Boqun Feng
On Sat, Jul 22, 2017 at 09:43:00PM -0700, Paul E. McKenney wrote: [...] > > Your priority seemed to be in reducing the chance of the "if" statement > > to be optimized away. So I suggested to use "extern" as a compromise. > Hi Akira, The problem is that, such a compromise doesn't help *develope

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-22 Thread Paul E. McKenney
On Sat, Jul 22, 2017 at 08:38:57AM +0900, Akira Yokosawa wrote: > On 2017/07/20 16:07:14 -0700, Paul E. McKenney wrote: > > On Fri, Jul 21, 2017 at 07:52:03AM +0900, Akira Yokosawa wrote: > >> On 2017/07/20 14:42:34 -0700, Paul E. McKenney wrote: > [...] > >>> For the compilers I know about at the

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-21 Thread Akira Yokosawa
On 2017/07/20 16:07:14 -0700, Paul E. McKenney wrote: > On Fri, Jul 21, 2017 at 07:52:03AM +0900, Akira Yokosawa wrote: >> On 2017/07/20 14:42:34 -0700, Paul E. McKenney wrote: [...] >>> For the compilers I know about at the present time, yes. >> >> So if I respin the patch with the extern, would y

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-21 Thread Paul E. McKenney
On Fri, Jul 21, 2017 at 08:24:40AM +0800, Boqun Feng wrote: > On Thu, Jul 20, 2017 at 04:07:14PM -0700, Paul E. McKenney wrote: > [...] > > > > > > So if I respin the patch with the extern, would you still feel reluctant? > > > > Yes, because I am not seeing how this change helps. What is this t

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Boqun Feng
On Thu, Jul 20, 2017 at 04:07:14PM -0700, Paul E. McKenney wrote: [...] > > > > So if I respin the patch with the extern, would you still feel reluctant? > > Yes, because I am not seeing how this change helps. What is this telling > the reader that the original did not, and how does it help the

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Paul E. McKenney
On Fri, Jul 21, 2017 at 07:52:03AM +0900, Akira Yokosawa wrote: > On 2017/07/20 14:42:34 -0700, Paul E. McKenney wrote: > > On Fri, Jul 21, 2017 at 06:12:56AM +0900, Akira Yokosawa wrote: > >> On 2017/07/20 09:11:52AM -0700, Paul E. McKenney wrote: > >>> On Thu, Jul 20, 2017 at 09:55:31PM +0900, Ak

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Akira Yokosawa
On 2017/07/20 14:42:34 -0700, Paul E. McKenney wrote: > On Fri, Jul 21, 2017 at 06:12:56AM +0900, Akira Yokosawa wrote: >> On 2017/07/20 09:11:52AM -0700, Paul E. McKenney wrote: >>> On Thu, Jul 20, 2017 at 09:55:31PM +0900, Akira Yokosawa wrote: On 2017/07/20 14:47, Paul E. McKenney wrote: >>

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Paul E. McKenney
On Fri, Jul 21, 2017 at 06:12:56AM +0900, Akira Yokosawa wrote: > On 2017/07/20 09:11:52AM -0700, Paul E. McKenney wrote: > > On Thu, Jul 20, 2017 at 09:55:31PM +0900, Akira Yokosawa wrote: > >> On 2017/07/20 14:47, Paul E. McKenney wrote: > >>> On Thu, Jul 20, 2017 at 09:31:41AM +0800, Boqun Feng

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Akira Yokosawa
On 2017/07/20 09:11:52AM -0700, Paul E. McKenney wrote: > On Thu, Jul 20, 2017 at 09:55:31PM +0900, Akira Yokosawa wrote: >> On 2017/07/20 14:47, Paul E. McKenney wrote: >>> On Thu, Jul 20, 2017 at 09:31:41AM +0800, Boqun Feng wrote: On Wed, Jul 19, 2017 at 02:56:02PM -0700, Paul E. McKenney w

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Paul E. McKenney
On Thu, Jul 20, 2017 at 09:55:31PM +0900, Akira Yokosawa wrote: > On 2017/07/20 14:47, Paul E. McKenney wrote: > > On Thu, Jul 20, 2017 at 09:31:41AM +0800, Boqun Feng wrote: > >> On Wed, Jul 19, 2017 at 02:56:02PM -0700, Paul E. McKenney wrote: > >>> On Thu, Jul 20, 2017 at 06:33:26AM +0900, Akira

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Akira Yokosawa
On 2017/07/20 14:47, Paul E. McKenney wrote: > On Thu, Jul 20, 2017 at 09:31:41AM +0800, Boqun Feng wrote: >> On Wed, Jul 19, 2017 at 02:56:02PM -0700, Paul E. McKenney wrote: >>> On Thu, Jul 20, 2017 at 06:33:26AM +0900, Akira Yokosawa wrote: On 2017/07/20 2:43, Paul E. McKenney wrote: >

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-20 Thread Paul E. McKenney
On Thu, Jul 20, 2017 at 02:14:34PM +0800, Boqun Feng wrote: > On Wed, Jul 19, 2017 at 10:47:04PM -0700, Paul E. McKenney wrote: > [...] > > > Hi Paul, > > > > > > I know the compiler could optimize atomics in very interesting ways, but > > > this case is about volatile, so I guess our case is stil

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-19 Thread Boqun Feng
On Wed, Jul 19, 2017 at 10:47:04PM -0700, Paul E. McKenney wrote: [...] > > Hi Paul, > > > > I know the compiler could optimize atomics in very interesting ways, but > > this case is about volatile, so I guess our case is still fine? ;-) > > Hello, Boqun, > > When I asked that question, the answ

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-19 Thread Paul E. McKenney
On Thu, Jul 20, 2017 at 09:31:41AM +0800, Boqun Feng wrote: > On Wed, Jul 19, 2017 at 02:56:02PM -0700, Paul E. McKenney wrote: > > On Thu, Jul 20, 2017 at 06:33:26AM +0900, Akira Yokosawa wrote: > > > On 2017/07/20 2:43, Paul E. McKenney wrote: > > > > On Mon, Jul 17, 2017 at 05:24:42PM +0900, Aki

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-19 Thread Boqun Feng
On Wed, Jul 19, 2017 at 02:56:02PM -0700, Paul E. McKenney wrote: > On Thu, Jul 20, 2017 at 06:33:26AM +0900, Akira Yokosawa wrote: > > On 2017/07/20 2:43, Paul E. McKenney wrote: > > > On Mon, Jul 17, 2017 at 05:24:42PM +0900, Akira Yokosawa wrote: > > >> >From b798b9b631e237d285aa8699da00bfb8ced3

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-19 Thread Paul E. McKenney
On Thu, Jul 20, 2017 at 06:33:26AM +0900, Akira Yokosawa wrote: > On 2017/07/20 2:43, Paul E. McKenney wrote: > > On Mon, Jul 17, 2017 at 05:24:42PM +0900, Akira Yokosawa wrote: > >> >From b798b9b631e237d285aa8699da00bfb8ced33bea Mon Sep 17 00:00:00 2001 > >> From: Akira Yokosawa > >> Date: Mon, 1

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-19 Thread Akira Yokosawa
On 2017/07/20 2:43, Paul E. McKenney wrote: > On Mon, Jul 17, 2017 at 05:24:42PM +0900, Akira Yokosawa wrote: >> >From b798b9b631e237d285aa8699da00bfb8ced33bea Mon Sep 17 00:00:00 2001 >> From: Akira Yokosawa >> Date: Mon, 17 Jul 2017 16:25:33 +0900 >> Subject: [PATCH] documentation: Fix two-CPU c

Re: [PATCH] documentation: Fix two-CPU control-dependency example

2017-07-19 Thread Paul E. McKenney
On Mon, Jul 17, 2017 at 05:24:42PM +0900, Akira Yokosawa wrote: > >From b798b9b631e237d285aa8699da00bfb8ced33bea Mon Sep 17 00:00:00 2001 > From: Akira Yokosawa > Date: Mon, 17 Jul 2017 16:25:33 +0900 > Subject: [PATCH] documentation: Fix two-CPU control-dependency example > > In commit 5646f7acc