linux-kernel - [PATCH 7/7] net/netfilter/nf_conntrack_core: Remove smp_mb() after spin

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Date:   Thu,  1 Sep 2016 17:04:17 +0200
From:   Manfred Spraul <manfred@...orfullife.com>
To:     benh@...nel.crashing.org, paulmck@...ux.vnet.ibm.com,
        Ingo Molnar <mingo@...e.hu>, Boqun Feng <boqun.feng@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, will.deacon@....com,
        1vier1@....de, Davidlohr Bueso <dave@...olabs.net>,
        Manfred Spraul <manfred@...orfullife.com>
Subject: [PATCH 7/7] net/netfilter/nf_conntrack_core: Remove smp_mb() after spin_lock().

As spin_unlock_wait() is defined as equivalent to spin_lock();
spin_unlock(), the smp_mb() after spin_lock() is not required.

Remove it.

Signed-off-by: Manfred Spraul <manfred@...orfullife.com>
---
 net/netfilter/nf_conntrack_core.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index c8a2d26..7a3b5e6 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -82,10 +82,7 @@ void nf_conntrack_lock(spinlock_t *lock) __acquires(lock)
 	/* 1) Acquire the lock */
 	spin_lock(lock);
 
-	/* 2) Order storing the lock and reading nf_conntrack_locks_all */
-	smp_mb();
-
-	/* 3) read nf_conntrack_locks_all, with ACQUIRE semantics */
+	/* 2) read nf_conntrack_locks_all, with ACQUIRE semantics */
 	if (likely(smp_load_acquire(&nf_conntrack_locks_all) == false))
 		return;
 
-- 
2.7.4