linux-kernel - [RFC][PATCH 2/4] tools/memory-model: Define applicable tags on operation in tools/...

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Date: Mon, 27 May 2024 17:22:51 +0200
From: Jonas Oberhauser <jonas.oberhauser@...weicloud.com>
To: paulmck@...nel.org
Cc: stern@...land.harvard.edu,
	parri.andrea@...il.com,
	will@...nel.org,
	peterz@...radead.org,
	boqun.feng@...il.com,
	npiggin@...il.com,
	dhowells@...hat.com,
	j.alglave@....ac.uk,
	luc.maranget@...ia.fr,
	akiyks@...il.com,
	dlustig@...dia.com,
	joel@...lfernandes.org,
	urezki@...il.com,
	quic_neeraju@...cinc.com,
	frederic@...nel.org,
	linux-kernel@...r.kernel.org,
	Jonas Oberhauser <jonas.oberhauser@...weicloud.com>
Subject: [RFC][PATCH 2/4] tools/memory-model: Define applicable tags on operation in tools/...

Herd7 transforms reads, writes, and read-modify-writes by eliminating
'acquire tags from writes, 'release tags from reads, and 'acquire,
'release, and 'mb tags from failed read-modify-writes. We emulate this
behavior by redefining Acquire, Release, and Mb sets in linux-kernel.bell
to explicitly exclude those combinations.

Herd7 furthermore adds 'noreturn tag to certain reads. Currently herd7
does not allow specifying the 'noreturn tag manually, but such manual
declaration (e.g., through a syntax __atomic_op{noreturn}) would add
invalid 'noreturn tags to writes; in preparation, we already also exclude
this combination.

Signed-off-by: Jonas Oberhauser <jonas.oberhauser@...weicloud.com>
---
 tools/memory-model/linux-kernel.bell | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/memory-model/linux-kernel.bell b/tools/memory-model/linux-kernel.bell
index 1b2444cdf8d1..08fa1ccb1328 100644
--- a/tools/memory-model/linux-kernel.bell
+++ b/tools/memory-model/linux-kernel.bell
@@ -36,6 +36,13 @@ enum Barriers = 'wmb (*smp_wmb*) ||
 		'after-srcu-read-unlock (*smp_mb__after_srcu_read_unlock*)
 instructions F[Barriers]
 
+(* Remove impossible tags, such as Acquire on a store or failed RMW *)
+let FailedRMW = RMW \ (domain(rmw) | range(rmw))
+let Acquire = Acquire \ W \ FailedRMW
+let Release = Release \ R \ FailedRMW
+let Mb = Mb \ FailedRMW
+let Noreturn = Noreturn \ W
+
 (* SRCU *)
 enum SRCU = 'srcu-lock || 'srcu-unlock || 'sync-srcu
 instructions SRCU[SRCU]
@@ -82,4 +89,4 @@ let Plain = M \ Marked
 let carry-dep = (data ; [~ Srcu-unlock] ; rfi)*
 let addr = carry-dep ; addr
 let ctrl = carry-dep ; ctrl
-let data = carry-dep ; data
+let data = carry-dep ; data
\ No newline at end of file
-- 
2.34.1