[PATCH 1/3] tools: memory-model: Prepare for data-race detection

[PATCH 1/3] tools: memory-model: Prepare for data-race detection

[Alan Stern]

This patch makes some slight alterations to linux-kernel.cat in
preparation for adding support for data-race detection to the
Linux-Kernel Memory Model.

	The definitions of relations involved in Acquire, Release, and
	unlock-lock ordering are moved up earlier in the source file.

	The rmb relation is factored through the new R4rmb class: the
	class of reads to which rmb will apply.

	The definition of the fence relation is moved earlier, and it
	is split up into read- and write-fences (rmb and wmb) and all
	the others.

This should not make any functional changes.

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

---


 tools/memory-model/linux-kernel.cat |   16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

Index: usb-devel/tools/memory-model/linux-kernel.cat
===================================================================
--- usb-devel.orig/tools/memory-model/linux-kernel.cat
+++ usb-devel/tools/memory-model/linux-kernel.cat
@@ -26,8 +26,14 @@ include "lock.cat"
 (* Basic relations *)
 (*******************)
 
+(* Release Acquire *)
+let acq-po = [Acquire] ; po ; [M]
+let po-rel = [M] ; po ; [Release]
+let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po
+
 (* Fences *)
-let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn]
+let R4rmb = R \ Noreturn	(* Reads for which rmb works *)
+let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb]
 let wmb = [W] ; fencerel(Wmb) ; [W]
 let mb = ([M] ; fencerel(Mb) ; [M]) |
 	([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
@@ -36,13 +42,10 @@ let mb = ([M] ; fencerel(Mb) ; [M]) |
 	([M] ; po ; [UL] ; (co | po) ; [LKW] ;
 		fencerel(After-unlock-lock) ; [M])
 let gp = po ; [Sync-rcu | Sync-srcu] ; po?
-
 let strong-fence = mb | gp
 
-(* Release Acquire *)
-let acq-po = [Acquire] ; po ; [M]
-let po-rel = [M] ; po ; [Release]
-let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po
+let nonrw-fence = strong-fence | po-rel | acq-po
+let fence = nonrw-fence | wmb | rmb
 
 (**********************************)
 (* Fundamental coherence ordering *)
@@ -65,7 +68,6 @@ let rwdep = (dep | ctrl) ; [W]
 let overwrite = co | fr
 let to-w = rwdep | (overwrite & int)
 let to-r = addr | (dep ; rfi)
-let fence = strong-fence | wmb | po-rel | rmb | acq-po
 let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int)
 
 (* Propagation: Ordering from release operations and strong fences. *)

Re: [PATCH 1/3] tools: memory-model: Prepare for data-race detection

[Paul E. McKenney]

On Mon, Apr 22, 2019 at 12:17:45PM -0400, Alan Stern wrote:
> This patch makes some slight alterations to linux-kernel.cat in
> preparation for adding support for data-race detection to the
> Linux-Kernel Memory Model.
> 
> 	The definitions of relations involved in Acquire, Release, and
> 	unlock-lock ordering are moved up earlier in the source file.
> 
> 	The rmb relation is factored through the new R4rmb class: the
> 	class of reads to which rmb will apply.
> 
> 	The definition of the fence relation is moved earlier, and it
> 	is split up into read- and write-fences (rmb and wmb) and all
> 	the others.
> 
> This should not make any functional changes.
> 
> Signed-off-by: Alan Stern <stern@rowland.harvard.edu>

Thank you, Alan, I have queued all three onto -rcu for review and testing.
FYI, I rebased my smp_mb__{before,after}_atomic() patch on top of yours
to avoid the conflict.

Which demonstrates non-commutativity of patches.  Your patches conflict
with mine, but mine does not conflict with yours.  ;-)

							Thanx, Paul

> ---
> 
> 
>  tools/memory-model/linux-kernel.cat |   16 +++++++++-------
>  1 file changed, 9 insertions(+), 7 deletions(-)
> 
> Index: usb-devel/tools/memory-model/linux-kernel.cat
> ===================================================================
> --- usb-devel.orig/tools/memory-model/linux-kernel.cat
> +++ usb-devel/tools/memory-model/linux-kernel.cat
> @@ -26,8 +26,14 @@ include "lock.cat"
>  (* Basic relations *)
>  (*******************)
>  
> +(* Release Acquire *)
> +let acq-po = [Acquire] ; po ; [M]
> +let po-rel = [M] ; po ; [Release]
> +let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po
> +
>  (* Fences *)
> -let rmb = [R \ Noreturn] ; fencerel(Rmb) ; [R \ Noreturn]
> +let R4rmb = R \ Noreturn	(* Reads for which rmb works *)
> +let rmb = [R4rmb] ; fencerel(Rmb) ; [R4rmb]
>  let wmb = [W] ; fencerel(Wmb) ; [W]
>  let mb = ([M] ; fencerel(Mb) ; [M]) |
>  	([M] ; fencerel(Before-atomic) ; [RMW] ; po? ; [M]) |
> @@ -36,13 +42,10 @@ let mb = ([M] ; fencerel(Mb) ; [M]) |
>  	([M] ; po ; [UL] ; (co | po) ; [LKW] ;
>  		fencerel(After-unlock-lock) ; [M])
>  let gp = po ; [Sync-rcu | Sync-srcu] ; po?
> -
>  let strong-fence = mb | gp
>  
> -(* Release Acquire *)
> -let acq-po = [Acquire] ; po ; [M]
> -let po-rel = [M] ; po ; [Release]
> -let po-unlock-rf-lock-po = po ; [UL] ; rf ; [LKR] ; po
> +let nonrw-fence = strong-fence | po-rel | acq-po
> +let fence = nonrw-fence | wmb | rmb
>  
>  (**********************************)
>  (* Fundamental coherence ordering *)
> @@ -65,7 +68,6 @@ let rwdep = (dep | ctrl) ; [W]
>  let overwrite = co | fr
>  let to-w = rwdep | (overwrite & int)
>  let to-r = addr | (dep ; rfi)
> -let fence = strong-fence | wmb | po-rel | rmb | acq-po
>  let ppo = to-r | to-w | fence | (po-unlock-rf-lock-po & int)
>  
>  (* Propagation: Ordering from release operations and strong fences. *)
> 
> 

Re: [PATCH 1/3] tools: memory-model: Prepare for data-race detection

[Alan Stern]

On Wed, 24 Apr 2019, Paul E. McKenney wrote:

> On Mon, Apr 22, 2019 at 12:17:45PM -0400, Alan Stern wrote:
> > This patch makes some slight alterations to linux-kernel.cat in
> > preparation for adding support for data-race detection to the
> > Linux-Kernel Memory Model.
> > 
> > 	The definitions of relations involved in Acquire, Release, and
> > 	unlock-lock ordering are moved up earlier in the source file.
> > 
> > 	The rmb relation is factored through the new R4rmb class: the
> > 	class of reads to which rmb will apply.
> > 
> > 	The definition of the fence relation is moved earlier, and it
> > 	is split up into read- and write-fences (rmb and wmb) and all
> > 	the others.
> > 
> > This should not make any functional changes.
> > 
> > Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> 
> Thank you, Alan, I have queued all three onto -rcu for review and testing.
> FYI, I rebased my smp_mb__{before,after}_atomic() patch on top of yours
> to avoid the conflict.
> 
> Which demonstrates non-commutativity of patches.  Your patches conflict
> with mine, but mine does not conflict with yours.  ;-)

:-)

Besides, who knows where we'll end up with the 
smp_mb__{before,after}_atomic stuff once Peter is done with it, anyway?

Alan

Re: [PATCH 1/3] tools: memory-model: Prepare for data-race detection

[Paul E. McKenney]

On Wed, Apr 24, 2019 at 10:24:42AM -0400, Alan Stern wrote:
> On Wed, 24 Apr 2019, Paul E. McKenney wrote:
> 
> > On Mon, Apr 22, 2019 at 12:17:45PM -0400, Alan Stern wrote:
> > > This patch makes some slight alterations to linux-kernel.cat in
> > > preparation for adding support for data-race detection to the
> > > Linux-Kernel Memory Model.
> > > 
> > > 	The definitions of relations involved in Acquire, Release, and
> > > 	unlock-lock ordering are moved up earlier in the source file.
> > > 
> > > 	The rmb relation is factored through the new R4rmb class: the
> > > 	class of reads to which rmb will apply.
> > > 
> > > 	The definition of the fence relation is moved earlier, and it
> > > 	is split up into read- and write-fences (rmb and wmb) and all
> > > 	the others.
> > > 
> > > This should not make any functional changes.
> > > 
> > > Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> > 
> > Thank you, Alan, I have queued all three onto -rcu for review and testing.
> > FYI, I rebased my smp_mb__{before,after}_atomic() patch on top of yours
> > to avoid the conflict.
> > 
> > Which demonstrates non-commutativity of patches.  Your patches conflict
> > with mine, but mine does not conflict with yours.  ;-)
> 
> :-)
> 
> Besides, who knows where we'll end up with the 
> smp_mb__{before,after}_atomic stuff once Peter is done with it, anyway?

True enough!

							Thanx, Paul