* [PATCH] Documentation: memory-barriers: Fix typo in the first example @ 2014-11-18 4:39 Srikanth Thokala 2014-11-27 6:49 ` Srikanth Thokala 0 siblings, 1 reply; 8+ messages in thread From: Srikanth Thokala @ 2014-11-18 4:39 UTC (permalink / raw) To: corbet; +Cc: linux-doc, linux-kernel, Srikanth Thokala In the first example, the loads into 'x' and 'y' on CPU 2 doesn't match the sequence of events described below it. To match the sequence of events, the values of 'A' and 'B' should be loaded into 'x' and 'y' respectively. Signed-off-by: Srikanth Thokala <sriku.linux@gmail.com> --- Documentation/memory-barriers.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 22a969c..2770bce 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -115,8 +115,8 @@ For example, consider the following sequence of events: CPU 1 CPU 2 =============== =============== { A == 1; B == 2 } - A = 3; x = B; - B = 4; y = A; + A = 3; x = A; + B = 4; y = B; The set of accesses as seen by the memory system in the middle can be arranged in 24 different combinations: -- 1.9.1 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example 2014-11-18 4:39 [PATCH] Documentation: memory-barriers: Fix typo in the first example Srikanth Thokala @ 2014-11-27 6:49 ` Srikanth Thokala 2014-12-02 21:15 ` Jonathan Corbet 0 siblings, 1 reply; 8+ messages in thread From: Srikanth Thokala @ 2014-11-27 6:49 UTC (permalink / raw) To: Jonathan Corbet; +Cc: linux-doc, linux-kernel@vger.kernel.org, Srikanth Thokala Hi, Kindly review the patch. Thanks Srikanth On Tue, Nov 18, 2014 at 10:09 AM, Srikanth Thokala <sriku.linux@gmail.com> wrote: > In the first example, the loads into 'x' and 'y' on CPU 2 doesn't > match the sequence of events described below it. To match the > sequence of events, the values of 'A' and 'B' should be loaded > into 'x' and 'y' respectively. > > Signed-off-by: Srikanth Thokala <sriku.linux@gmail.com> > --- > Documentation/memory-barriers.txt | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt > index 22a969c..2770bce 100644 > --- a/Documentation/memory-barriers.txt > +++ b/Documentation/memory-barriers.txt > @@ -115,8 +115,8 @@ For example, consider the following sequence of events: > CPU 1 CPU 2 > =============== =============== > { A == 1; B == 2 } > - A = 3; x = B; > - B = 4; y = A; > + A = 3; x = A; > + B = 4; y = B; > > The set of accesses as seen by the memory system in the middle can be arranged > in 24 different combinations: > -- > 1.9.1 > ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example 2014-11-27 6:49 ` Srikanth Thokala @ 2014-12-02 21:15 ` Jonathan Corbet 2014-12-02 21:50 ` Paul E. McKenney 0 siblings, 1 reply; 8+ messages in thread From: Jonathan Corbet @ 2014-12-02 21:15 UTC (permalink / raw) To: Srikanth Thokala Cc: linux-doc, linux-kernel@vger.kernel.org, Paul E. McKenney On Thu, 27 Nov 2014 12:19:26 +0530 Srikanth Thokala <sriku.linux@gmail.com> wrote: > Hi, > > Kindly review the patch. To me it looks right. Something like this, though, needs an ack from Paul (cc'd) before I can be really confident. Paul...? jon > Thanks > Srikanth > > On Tue, Nov 18, 2014 at 10:09 AM, Srikanth Thokala > <sriku.linux@gmail.com> wrote: > > In the first example, the loads into 'x' and 'y' on CPU 2 doesn't > > match the sequence of events described below it. To match the > > sequence of events, the values of 'A' and 'B' should be loaded > > into 'x' and 'y' respectively. > > > > Signed-off-by: Srikanth Thokala <sriku.linux@gmail.com> > > --- > > Documentation/memory-barriers.txt | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt > > index 22a969c..2770bce 100644 > > --- a/Documentation/memory-barriers.txt > > +++ b/Documentation/memory-barriers.txt > > @@ -115,8 +115,8 @@ For example, consider the following sequence of events: > > CPU 1 CPU 2 > > =============== =============== > > { A == 1; B == 2 } > > - A = 3; x = B; > > - B = 4; y = A; > > + A = 3; x = A; > > + B = 4; y = B; > > > > The set of accesses as seen by the memory system in the middle can be arranged > > in 24 different combinations: > > -- > > 1.9.1 > > > ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example 2014-12-02 21:15 ` Jonathan Corbet @ 2014-12-02 21:50 ` Paul E. McKenney 2014-12-02 22:01 ` Jonathan Corbet 0 siblings, 1 reply; 8+ messages in thread From: Paul E. McKenney @ 2014-12-02 21:50 UTC (permalink / raw) To: Jonathan Corbet; +Cc: Srikanth Thokala, linux-doc, linux-kernel@vger.kernel.org On Tue, Dec 02, 2014 at 04:15:19PM -0500, Jonathan Corbet wrote: > On Thu, 27 Nov 2014 12:19:26 +0530 > Srikanth Thokala <sriku.linux@gmail.com> wrote: > > > Hi, > > > > Kindly review the patch. > > To me it looks right. Something like this, though, needs an ack from > Paul (cc'd) before I can be really confident. Paul...? I am guessing that this patch is against an old version of this file (there have been two patches applied to this example in the last six months). I believe that the current version is correct, in other words, that Alexey Dobriyan and Pranith Kumar beat you to this one. ;-) Please see below for the current version, which is in -tip as of November 20th. Thanx, Paul > jon > > > Thanks > > Srikanth > > > > On Tue, Nov 18, 2014 at 10:09 AM, Srikanth Thokala > > <sriku.linux@gmail.com> wrote: > > > In the first example, the loads into 'x' and 'y' on CPU 2 doesn't > > > match the sequence of events described below it. To match the > > > sequence of events, the values of 'A' and 'B' should be loaded > > > into 'x' and 'y' respectively. > > > > > > Signed-off-by: Srikanth Thokala <sriku.linux@gmail.com> > > > --- > > > Documentation/memory-barriers.txt | 4 ++-- > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt > > > index 22a969c..2770bce 100644 > > > --- a/Documentation/memory-barriers.txt > > > +++ b/Documentation/memory-barriers.txt > > > @@ -115,8 +115,8 @@ For example, consider the following sequence of events: > > > CPU 1 CPU 2 > > > =============== =============== > > > { A == 1; B == 2 } > > > - A = 3; x = B; > > > - B = 4; y = A; > > > + A = 3; x = A; > > > + B = 4; y = B; > > > > > > The set of accesses as seen by the memory system in the middle can be arranged > > > in 24 different combinations: For example, consider the following sequence of events: CPU 1 CPU 2 =============== =============== { A == 1; B == 2 } A = 3; x = B; B = 4; y = A; The set of accesses as seen by the memory system in the middle can be arranged in 24 different combinations: STORE A=3, STORE B=4, y=LOAD A->3, x=LOAD B->4 STORE A=3, STORE B=4, x=LOAD B->4, y=LOAD A->3 STORE A=3, y=LOAD A->3, STORE B=4, x=LOAD B->4 STORE A=3, y=LOAD A->3, x=LOAD B->2, STORE B=4 STORE A=3, x=LOAD B->2, STORE B=4, y=LOAD A->3 STORE A=3, x=LOAD B->2, y=LOAD A->3, STORE B=4 STORE B=4, STORE A=3, y=LOAD A->3, x=LOAD B->4 STORE B=4, ... ... and can thus result in four different combinations of values: x == 2, y == 1 x == 2, y == 3 x == 4, y == 1 x == 4, y == 3 ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example 2014-12-02 21:50 ` Paul E. McKenney @ 2014-12-02 22:01 ` Jonathan Corbet 2014-12-02 22:09 ` Paul E. McKenney 0 siblings, 1 reply; 8+ messages in thread From: Jonathan Corbet @ 2014-12-02 22:01 UTC (permalink / raw) To: Paul E. McKenney Cc: Srikanth Thokala, linux-doc, linux-kernel@vger.kernel.org On Tue, 2 Dec 2014 13:50:06 -0800 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote: > I am guessing that this patch is against an old version of this file > (there have been two patches applied to this example in the last six > months). I believe that the current version is correct, in other words, > that Alexey Dobriyan and Pranith Kumar beat you to this one. ;-) I thought it looked familiar somehow...patch dropped. I guess it's comforting to know that so many people are reading that file so closely, but it's a little scary too...:) Thanks, jon ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example 2014-12-02 22:01 ` Jonathan Corbet @ 2014-12-02 22:09 ` Paul E. McKenney 2014-12-03 0:15 ` Måns Rullgård 0 siblings, 1 reply; 8+ messages in thread From: Paul E. McKenney @ 2014-12-02 22:09 UTC (permalink / raw) To: Jonathan Corbet; +Cc: Srikanth Thokala, linux-doc, linux-kernel@vger.kernel.org On Tue, Dec 02, 2014 at 05:01:36PM -0500, Jonathan Corbet wrote: > On Tue, 2 Dec 2014 13:50:06 -0800 > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote: > > > I am guessing that this patch is against an old version of this file > > (there have been two patches applied to this example in the last six > > months). I believe that the current version is correct, in other words, > > that Alexey Dobriyan and Pranith Kumar beat you to this one. ;-) > > I thought it looked familiar somehow...patch dropped. > > I guess it's comforting to know that so many people are reading that file > so closely, but it's a little scary too...:) What scares me is that so few people appear to have been reading it earlier on. ;-) Thanx, Paul ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example 2014-12-02 22:09 ` Paul E. McKenney @ 2014-12-03 0:15 ` Måns Rullgård 2014-12-03 0:27 ` Paul E. McKenney 0 siblings, 1 reply; 8+ messages in thread From: Måns Rullgård @ 2014-12-03 0:15 UTC (permalink / raw) To: Paul E. McKenney Cc: Jonathan Corbet, Srikanth Thokala, linux-doc, linux-kernel@vger.kernel.org "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes: > On Tue, Dec 02, 2014 at 05:01:36PM -0500, Jonathan Corbet wrote: >> On Tue, 2 Dec 2014 13:50:06 -0800 >> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote: >> >> > I am guessing that this patch is against an old version of this file >> > (there have been two patches applied to this example in the last six >> > months). I believe that the current version is correct, in other words, >> > that Alexey Dobriyan and Pranith Kumar beat you to this one. ;-) >> >> I thought it looked familiar somehow...patch dropped. >> >> I guess it's comforting to know that so many people are reading that file >> so closely, but it's a little scary too...:) > > What scares me is that so few people appear to have been reading it > earlier on. ;-) Or they read it but failed to understand it. Not sure which is scarier. Those are probably the Evil Vendor Tree developers who apparently think "this is hard, best put volatile and barriers _everywhere_ and hope for the best." -- Måns Rullgård mans@mansr.com ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] Documentation: memory-barriers: Fix typo in the first example 2014-12-03 0:15 ` Måns Rullgård @ 2014-12-03 0:27 ` Paul E. McKenney 0 siblings, 0 replies; 8+ messages in thread From: Paul E. McKenney @ 2014-12-03 0:27 UTC (permalink / raw) To: Måns Rullgård Cc: Jonathan Corbet, Srikanth Thokala, linux-doc, linux-kernel@vger.kernel.org On Wed, Dec 03, 2014 at 12:15:50AM +0000, Måns Rullgård wrote: > "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> writes: > > > On Tue, Dec 02, 2014 at 05:01:36PM -0500, Jonathan Corbet wrote: > >> On Tue, 2 Dec 2014 13:50:06 -0800 > >> "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote: > >> > >> > I am guessing that this patch is against an old version of this file > >> > (there have been two patches applied to this example in the last six > >> > months). I believe that the current version is correct, in other words, > >> > that Alexey Dobriyan and Pranith Kumar beat you to this one. ;-) > >> > >> I thought it looked familiar somehow...patch dropped. > >> > >> I guess it's comforting to know that so many people are reading that file > >> so closely, but it's a little scary too...:) > > > > What scares me is that so few people appear to have been reading it > > earlier on. ;-) > > Or they read it but failed to understand it. Not sure which is scarier. > > Those are probably the Evil Vendor Tree developers who apparently think > "this is hard, best put volatile and barriers _everywhere_ and hope for > the best." "This is hard!!! Let's go do some single-threaded programming!" ;-) Thanx, Paul ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2014-12-03 0:27 UTC | newest] Thread overview: 8+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2014-11-18 4:39 [PATCH] Documentation: memory-barriers: Fix typo in the first example Srikanth Thokala 2014-11-27 6:49 ` Srikanth Thokala 2014-12-02 21:15 ` Jonathan Corbet 2014-12-02 21:50 ` Paul E. McKenney 2014-12-02 22:01 ` Jonathan Corbet 2014-12-02 22:09 ` Paul E. McKenney 2014-12-03 0:15 ` Måns Rullgård 2014-12-03 0:27 ` Paul E. McKenney
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