tools/memory-model: Make read_foo_diagnostic() more clearly diagnostic

paulmckrcu · paulmckrcu · commit 1846a7fa767f · 2021-07-20T13:52:03.000-07:00
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 &lt;manfred@colorfullife.com&gt;
Signed-off-by: Paul E. McKenney &lt;paulmck@kernel.org&gt;
diff --git 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

Original file line number	Diff line number	Diff line change
`@@ -259,9 +259,9 @@ diagnostic purposes. The code might look as follows:`
`259`	`259`	`return ret;`
`260`	`260`	`}`
`261`	`261`
`262`		`- int read_foo_diagnostic(void)`
	`262`	`+ void read_foo_diagnostic(void)`
`263`	`263`	`{`
`264`		`- return data_race(foo);`
	`264`	`+ pr_info("Current value of foo: %d\n", data_race(foo));`
`265`	`265`	`}`
`266`	`266`
`267`	`267`	`The reader-writer lock prevents the compiler from introducing concurrency`