linux-kernel - [PATCH memory-model 1/4] tools/memory-model: Make read_foo

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Date:   Wed, 21 Jul 2021 14:10:00 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        kernel-team@...com, mingo@...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, "Paul E. McKenney" <paulmck@...nel.org>,
        Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH memory-model 1/4] tools/memory-model: Make read_foo_diagnostic() more clearly diagnostic

The current definition of read_foo_diagnostic() in the "Lock Protection
With Lockless Diagnostic Access" section returns a value, which could
be use for any purpose.  This could mislead people into incorrectly
using data_race() in cases where READ_ONCE() is required.  This commit
therefore makes read_foo_diagnostic() simply print the value read.

Reported-by: Manfred Spraul <manfred@...orfullife.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 tools/memory-model/Documentation/access-marking.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/memory-model/Documentation/access-marking.txt b/tools/memory-model/Documentation/access-marking.txt
index 1ab189f51f55d..58bff26198767 100644
--- a/tools/memory-model/Documentation/access-marking.txt
+++ b/tools/memory-model/Documentation/access-marking.txt
@@ -259,9 +259,9 @@ diagnostic purposes.  The code might look as follows:
 		return ret;
 	}
 
-	int read_foo_diagnostic(void)
+	void read_foo_diagnostic(void)
 	{
-		return data_race(foo);
+		pr_info("Current value of foo: %d\n", data_race(foo));
 	}
 
 The reader-writer lock prevents the compiler from introducing concurrency
-- 
2.31.1.189.g2e36527f23