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* [PATCH] Use term cumul-fence instead of fence in ->prop ordering example
@ 2019-07-29 12:36 Joel Fernandes (Google)
  2019-07-29 20:41 ` Alan Stern
  0 siblings, 1 reply; 3+ messages in thread
From: Joel Fernandes (Google) @ 2019-07-29 12:36 UTC (permalink / raw)
  To: linux-kernel
  Cc: Joel Fernandes (Google),
	Alan Stern, Akira Yokosawa, Andrea Parri, Boqun Feng,
	Daniel Lustig, David Howells, Ingo Molnar, Jade Alglave,
	linux-arch, Luc Maranget, Nicholas Piggin, Paul E. McKenney,
	Peter Zijlstra, Will Deacon

To reduce ambiguity in the more exotic ->prop ordering example, let us
use the term cumul-fence instead fence for the 2 fences, so that the
implict ->rfe on loads/stores to Y are covered by the description.

Link: https://lore.kernel.org/lkml/20190729121745.GA140682@google.com

Suggested-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 tools/memory-model/Documentation/explanation.txt | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/memory-model/Documentation/explanation.txt b/tools/memory-model/Documentation/explanation.txt
index 68caa9a976d0..634dc6db26c4 100644
--- a/tools/memory-model/Documentation/explanation.txt
+++ b/tools/memory-model/Documentation/explanation.txt
@@ -1302,7 +1302,7 @@ followed by an arbitrary number of cumul-fence links, ending with an
 rfe link.  You can concoct more exotic examples, containing more than
 one fence, although this quickly leads to diminishing returns in terms
 of complexity.  For instance, here's an example containing a coe link
-followed by two fences and an rfe link, utilizing the fact that
+followed by two cumul-fences and an rfe link, utilizing the fact that
 release fences are A-cumulative:
 
 	int x, y, z;
@@ -1334,10 +1334,10 @@ If x = 2, r0 = 1, and r2 = 1 after this code runs then there is a prop
 link from P0's store to its load.  This is because P0's store gets
 overwritten by P1's store since x = 2 at the end (a coe link), the
 smp_wmb() ensures that P1's store to x propagates to P2 before the
-store to y does (the first fence), the store to y propagates to P2
+store to y does (the first cumul-fence), the store to y propagates to P2
 before P2's load and store execute, P2's smp_store_release()
 guarantees that the stores to x and y both propagate to P0 before the
-store to z does (the second fence), and P0's load executes after the
+store to z does (the second cumul-fence), and P0's load executes after the
 store to z has propagated to P0 (an rfe link).
 
 In summary, the fact that the hb relation links memory access events
-- 
2.22.0.709.g102302147b-goog


^ permalink raw reply related	[flat|nested] 3+ messages in thread

* Re: [PATCH] Use term cumul-fence instead of fence in ->prop ordering example
  2019-07-29 12:36 [PATCH] Use term cumul-fence instead of fence in ->prop ordering example Joel Fernandes (Google)
@ 2019-07-29 20:41 ` Alan Stern
  2019-07-30 15:58   ` Paul E. McKenney
  0 siblings, 1 reply; 3+ messages in thread
From: Alan Stern @ 2019-07-29 20:41 UTC (permalink / raw)
  To: Joel Fernandes (Google)
  Cc: linux-kernel, Akira Yokosawa, Andrea Parri, Boqun Feng,
	Daniel Lustig, David Howells, Ingo Molnar, Jade Alglave,
	linux-arch, Luc Maranget, Nicholas Piggin, Paul E. McKenney,
	Peter Zijlstra, Will Deacon

On Mon, 29 Jul 2019, Joel Fernandes (Google) wrote:

> To reduce ambiguity in the more exotic ->prop ordering example, let us
> use the term cumul-fence instead fence for the 2 fences, so that the
> implict ->rfe on loads/stores to Y are covered by the description.
> 
> Link: https://lore.kernel.org/lkml/20190729121745.GA140682@google.com
> 
> Suggested-by: Alan Stern <stern@rowland.harvard.edu>
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> ---
>  tools/memory-model/Documentation/explanation.txt | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/memory-model/Documentation/explanation.txt b/tools/memory-model/Documentation/explanation.txt
> index 68caa9a976d0..634dc6db26c4 100644
> --- a/tools/memory-model/Documentation/explanation.txt
> +++ b/tools/memory-model/Documentation/explanation.txt
> @@ -1302,7 +1302,7 @@ followed by an arbitrary number of cumul-fence links, ending with an
>  rfe link.  You can concoct more exotic examples, containing more than
>  one fence, although this quickly leads to diminishing returns in terms
>  of complexity.  For instance, here's an example containing a coe link
> -followed by two fences and an rfe link, utilizing the fact that
> +followed by two cumul-fences and an rfe link, utilizing the fact that
>  release fences are A-cumulative:
>  
>  	int x, y, z;
> @@ -1334,10 +1334,10 @@ If x = 2, r0 = 1, and r2 = 1 after this code runs then there is a prop
>  link from P0's store to its load.  This is because P0's store gets
>  overwritten by P1's store since x = 2 at the end (a coe link), the
>  smp_wmb() ensures that P1's store to x propagates to P2 before the
> -store to y does (the first fence), the store to y propagates to P2
> +store to y does (the first cumul-fence), the store to y propagates to P2
>  before P2's load and store execute, P2's smp_store_release()
>  guarantees that the stores to x and y both propagate to P0 before the
> -store to z does (the second fence), and P0's load executes after the
> +store to z does (the second cumul-fence), and P0's load executes after the
>  store to z has propagated to P0 (an rfe link).
>  
>  In summary, the fact that the hb relation links memory access events

Acked-by: Alan Stern <stern@rowland.harvard.edu>


^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: [PATCH] Use term cumul-fence instead of fence in ->prop ordering example
  2019-07-29 20:41 ` Alan Stern
@ 2019-07-30 15:58   ` Paul E. McKenney
  0 siblings, 0 replies; 3+ messages in thread
From: Paul E. McKenney @ 2019-07-30 15:58 UTC (permalink / raw)
  To: Alan Stern
  Cc: Joel Fernandes (Google),
	linux-kernel, Akira Yokosawa, Andrea Parri, Boqun Feng,
	Daniel Lustig, David Howells, Ingo Molnar, Jade Alglave,
	linux-arch, Luc Maranget, Nicholas Piggin, Peter Zijlstra,
	Will Deacon

On Mon, Jul 29, 2019 at 04:41:34PM -0400, Alan Stern wrote:
> On Mon, 29 Jul 2019, Joel Fernandes (Google) wrote:
> 
> > To reduce ambiguity in the more exotic ->prop ordering example, let us
> > use the term cumul-fence instead fence for the 2 fences, so that the
> > implict ->rfe on loads/stores to Y are covered by the description.
> > 
> > Link: https://lore.kernel.org/lkml/20190729121745.GA140682@google.com
> > 
> > Suggested-by: Alan Stern <stern@rowland.harvard.edu>
> > Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
> > ---
> >  tools/memory-model/Documentation/explanation.txt | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/memory-model/Documentation/explanation.txt b/tools/memory-model/Documentation/explanation.txt
> > index 68caa9a976d0..634dc6db26c4 100644
> > --- a/tools/memory-model/Documentation/explanation.txt
> > +++ b/tools/memory-model/Documentation/explanation.txt
> > @@ -1302,7 +1302,7 @@ followed by an arbitrary number of cumul-fence links, ending with an
> >  rfe link.  You can concoct more exotic examples, containing more than
> >  one fence, although this quickly leads to diminishing returns in terms
> >  of complexity.  For instance, here's an example containing a coe link
> > -followed by two fences and an rfe link, utilizing the fact that
> > +followed by two cumul-fences and an rfe link, utilizing the fact that
> >  release fences are A-cumulative:
> >  
> >  	int x, y, z;
> > @@ -1334,10 +1334,10 @@ If x = 2, r0 = 1, and r2 = 1 after this code runs then there is a prop
> >  link from P0's store to its load.  This is because P0's store gets
> >  overwritten by P1's store since x = 2 at the end (a coe link), the
> >  smp_wmb() ensures that P1's store to x propagates to P2 before the
> > -store to y does (the first fence), the store to y propagates to P2
> > +store to y does (the first cumul-fence), the store to y propagates to P2
> >  before P2's load and store execute, P2's smp_store_release()
> >  guarantees that the stores to x and y both propagate to P0 before the
> > -store to z does (the second fence), and P0's load executes after the
> > +store to z does (the second cumul-fence), and P0's load executes after the
> >  store to z has propagated to P0 (an rfe link).
> >  
> >  In summary, the fact that the hb relation links memory access events
> 
> Acked-by: Alan Stern <stern@rowland.harvard.edu>

Queued with Alan's ack, thank you both!

							Thanx, Paul

^ permalink raw reply	[flat|nested] 3+ messages in thread

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2019-07-29 12:36 [PATCH] Use term cumul-fence instead of fence in ->prop ordering example Joel Fernandes (Google)
2019-07-29 20:41 ` Alan Stern
2019-07-30 15:58   ` Paul E. McKenney

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