linux-kernel - Re: [PATCH] docs: rcu: Make reader aware of rcu_dereference

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Date:   Tue, 9 Oct 2018 21:01:59 -0700
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, tytso@....edu,
        Jonathan Corbet <corbet@....net>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-doc@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] docs: rcu: Make reader aware of rcu_dereference_protected

On Tue, Oct 09, 2018 at 08:09:06PM -0700, Paul E. McKenney wrote:
> On Mon, Oct 08, 2018 at 06:33:41PM -0700, Joel Fernandes (Google) wrote:
> > whatisRCU says rcu_dereference cannot be used outside of rcu read lock
> > protected sections. Its better to mention rcu_dereference_protected when
> > it says that, so that the new reader is aware of this API and is not led
> > to believing that all RCU dereferences in all situations have to be
> > protected by a rcu_read_lock() and rcu_read_unlock().
> > 
> > Cc: tytso@....edu
> > Suggested-by: tytso@....edu
> > Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> 
> Good stuff!  I queued and pushed this with some wordsmithing.  Could
> you please check for my having messed something up?

One small nit which the below diff should fix, but otherwise looks good to
me, thanks!

 - Joel

----8<----

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index 38044c978e54..093b85ad49eb 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -297,7 +297,7 @@ rcu_dereference()
 	protected by locks acquired by the update-side code.  This variant
 	avoids the lockdep warning that would happen when using (for
 	example) rcu_dereference() without rcu_read_lock() protection.
-	Using rcu_dereference_protected() also have the advantage
+	Using rcu_dereference_protected() also has the advantage
 	of permitting compiler optimizations that rcu_dereference()
 	must prohibit.	The rcu_dereference_protected() variant takes
 	a lockdep expression to indicate which locks must be acquired