tools/memory-model: Prepare for data-race detection

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>
Reviewed-by: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

tools/memory-model/linux-kernel.cat

@@ -24,8 +24,14 @@ 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]) |
@@ -34,13 +40,10 @@ 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 *)
@@ -63,7 +66,6 @@ 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. *)