linux-kernel - [RFC PATCH 09/21] list: Remove unnecessary WRITE_ONCE() from hlist_bl_add

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Date:   Tue, 24 Mar 2020 15:36:31 +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 09/21] list: Remove unnecessary WRITE_ONCE() from hlist_bl_add_before()

There is no need to use WRITE_ONCE() when inserting into a non-RCU
protected list.

Cc: Paul E. McKenney <paulmck@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Will Deacon <will@...nel.org>
---
 include/linux/list_bl.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
index 1804fdb84dda..c93e7e3aa8fc 100644
--- a/include/linux/list_bl.h
+++ b/include/linux/list_bl.h
@@ -91,15 +91,15 @@ static inline void hlist_bl_add_before(struct hlist_bl_node *n,
 				       struct hlist_bl_node *next)
 {
 	struct hlist_bl_node **pprev = next->pprev;
+	unsigned long val;
 
 	n->pprev = pprev;
 	n->next = next;
 	next->pprev = &n->next;
 
 	/* pprev may be `first`, so be careful not to lose the lock bit */
-	WRITE_ONCE(*pprev,
-		   (struct hlist_bl_node *)
-			((uintptr_t)n | ((uintptr_t)*pprev & LIST_BL_LOCKMASK)));
+	val = (unsigned long)n | ((unsigned long)*pprev & LIST_BL_LOCKMASK);
+	*pprev = (struct hlist_bl_node *)val;
 }
 
 static inline void hlist_bl_add_behind(struct hlist_bl_node *n,
-- 
2.20.1