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From: "Paul E. McKenney" <paulmck@kernel.org>
To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	kernel-team@meta.com, mingo@kernel.org
Cc: stern@rowland.harvard.edu, parri.andrea@gmail.com,
	will@kernel.org, peterz@infradead.org, boqun.feng@gmail.com,
	npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk,
	luc.maranget@inria.fr, akiyks@gmail.com,
	"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH memory-model 3/8] tools/memory-model: Add smp_mb__after_srcu_read_unlock()
Date: Mon, 20 Mar 2023 18:02:41 -0700	[thread overview]
Message-ID: <20230321010246.50960-3-paulmck@kernel.org> (raw)
In-Reply-To: <778147e4-ccab-40cf-b6ef-31abe4e3f6b7@paulmck-laptop>

This commit adds support for smp_mb__after_srcu_read_unlock(), which,
when combined with a prior srcu_read_unlock(), implies a full memory
barrier.  No ordering is guaranteed to accesses between the two, and
placing accesses between is bad practice in any case.

Tests may be found at https://github.com/paulmckrcu/litmus in files
matching manual/kernel/C-srcu-mb-*.litmus.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 tools/memory-model/linux-kernel.bell | 3 ++-
 tools/memory-model/linux-kernel.cat  | 3 ++-
 tools/memory-model/linux-kernel.def  | 1 +
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/memory-model/linux-kernel.bell b/tools/memory-model/linux-kernel.bell
index dc464854d28a..b92fdf7f6eeb 100644
--- a/tools/memory-model/linux-kernel.bell
+++ b/tools/memory-model/linux-kernel.bell
@@ -31,7 +31,8 @@ enum Barriers = 'wmb (*smp_wmb*) ||
 		'before-atomic (*smp_mb__before_atomic*) ||
 		'after-atomic (*smp_mb__after_atomic*) ||
 		'after-spinlock (*smp_mb__after_spinlock*) ||
-		'after-unlock-lock (*smp_mb__after_unlock_lock*)
+		'after-unlock-lock (*smp_mb__after_unlock_lock*) ||
+		'after-srcu-read-unlock (*smp_mb__after_srcu_read_unlock*)
 instructions F[Barriers]
 
 (* SRCU *)
diff --git a/tools/memory-model/linux-kernel.cat b/tools/memory-model/linux-kernel.cat
index 6e531457bb73..3a4d3b49e85c 100644
--- a/tools/memory-model/linux-kernel.cat
+++ b/tools/memory-model/linux-kernel.cat
@@ -49,7 +49,8 @@ let mb = ([M] ; fencerel(Mb) ; [M]) |
  * also affected by the fence.
  *)
 	([M] ; po-unlock-lock-po ;
-		[After-unlock-lock] ; po ; [M])
+		[After-unlock-lock] ; po ; [M]) |
+	([M] ; po? ; [Srcu-unlock] ; fencerel(After-srcu-read-unlock) ; [M])
 let gp = po ; [Sync-rcu | Sync-srcu] ; po?
 let strong-fence = mb | gp
 
diff --git a/tools/memory-model/linux-kernel.def b/tools/memory-model/linux-kernel.def
index ef0f3c1850de..a6b6fbc9d0b2 100644
--- a/tools/memory-model/linux-kernel.def
+++ b/tools/memory-model/linux-kernel.def
@@ -24,6 +24,7 @@ smp_mb__before_atomic() { __fence{before-atomic}; }
 smp_mb__after_atomic() { __fence{after-atomic}; }
 smp_mb__after_spinlock() { __fence{after-spinlock}; }
 smp_mb__after_unlock_lock() { __fence{after-unlock-lock}; }
+smp_mb__after_srcu_read_unlock() { __fence{after-srcu-read-unlock}; }
 barrier() { __fence{barrier}; }
 
 // Exchange
-- 
2.40.0.rc2


  parent reply	other threads:[~2023-03-21  1:03 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-21  1:02 [PATCH memory-model 0/8] LKMM updates for v6.4 Paul E. McKenney
2023-03-21  1:02 ` [PATCH memory-model 1/8] tools/memory-model: Update some warning labels Paul E. McKenney
2023-03-22  0:51   ` Andrea Parri
2023-03-21  1:02 ` [PATCH memory-model 2/8] tools/memory-model: Unify UNLOCK+LOCK pairings to po-unlock-lock-po Paul E. McKenney
2023-03-22  0:59   ` Andrea Parri
2023-03-22 18:06     ` Paul E. McKenney
2023-03-21  1:02 ` Paul E. McKenney [this message]
2023-03-21  1:02 ` [PATCH memory-model 4/8] tools/memory-model: Restrict to-r to read-read address dependency Paul E. McKenney
2023-03-22  0:53   ` Andrea Parri
2023-03-21  1:02 ` [PATCH memory-model 5/8] tools/memory-model: Provide exact SRCU semantics Paul E. McKenney
2023-03-22  1:07   ` Andrea Parri
2023-03-22  1:13     ` Alan Stern
2023-03-21  1:02 ` [PATCH memory-model 6/8] tools/memory-model: Make ppo a subrelation of po Paul E. McKenney
2023-03-21  1:02 ` [PATCH memory-model 7/8] tools/memory-model: Add documentation about SRCU read-side critical sections Paul E. McKenney
2023-03-22  1:40   ` Andrea Parri
2023-03-22  2:17     ` Joel Fernandes
2023-03-22 14:30     ` Alan Stern
2023-03-22 18:02     ` Paul E. McKenney
2023-03-21  1:02 ` [PATCH memory-model 8/8] Documentation: litmus-tests: Correct spelling Paul E. McKenney

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