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Message-Id: <20200324153643.15527-6-will@kernel.org>
Date: Tue, 24 Mar 2020 15:36:27 +0000
From: Will Deacon <will@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Will Deacon <will@...nel.org>,
Eric Dumazet <edumazet@...gle.com>,
Jann Horn <jannh@...gle.com>,
Kees Cook <keescook@...omium.org>,
Maddie Stone <maddiestone@...gle.com>,
Marco Elver <elver@...gle.com>,
"Paul E . McKenney" <paulmck@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
kernel-team@...roid.com,
kernel-hardening@...ts.openwall.com
Subject: [RFC PATCH 05/21] list: Comment missing WRITE_ONCE() in __list_del()
Although __list_del() is called from the RCU list implementation, it
omits WRITE_ONCE() when updating the 'prev' pointer for the 'next' node.
This is reasonable because concurrent RCU readers only access the 'next'
pointers.
Although it's obvious after reading the code, add a comment.
Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Will Deacon <will@...nel.org>
---
include/linux/list.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/linux/list.h b/include/linux/list.h
index 4d9f5f9ed1a8..ec1f780d1449 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -109,6 +109,7 @@ static inline void list_add_tail(struct list_head *new, struct list_head *head)
*/
static inline void __list_del(struct list_head * prev, struct list_head * next)
{
+ /* RCU readers don't read the 'prev' pointer */
next->prev = prev;
WRITE_ONCE(prev->next, next);
}
--
2.20.1
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