4 files changed, 33 insertions, 28 deletions

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index 002743ea509c..8112893037bd 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -734,7 +734,7 @@ static void hidp_stop(struct hid_device *hid)
 	hid->claimed = 0;
 }
 
-static struct hid_ll_driver hidp_hid_driver = {
+struct hid_ll_driver hidp_hid_driver = {
 	.parse = hidp_parse,
 	.start = hidp_start,
 	.stop = hidp_stop,
@@ -743,6 +743,7 @@ static struct hid_ll_driver hidp_hid_driver = {
 	.raw_request = hidp_raw_request,
 	.output_report = hidp_output_report,
 };
+EXPORT_SYMBOL_GPL(hidp_hid_driver);
 
 /* This function sets up the hid device. It does not add it
    to the HID system. That is done in hidp_add_connection(). */
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index f900cdd0fbfb..db1c9e78c83c 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1814,8 +1814,7 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 static struct static_key udp_encap_needed __read_mostly;
 void udp_encap_enable(void)
 {
-	if (!static_key_enabled(&udp_encap_needed))
-		static_key_slow_inc(&udp_encap_needed);
+	static_key_enable(&udp_encap_needed);
 }
 EXPORT_SYMBOL(udp_encap_enable);
 
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 42ebb9ad46cc..e2ecfb137297 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -579,8 +579,7 @@ static __inline__ void udpv6_err(struct sk_buff *skb,
 static struct static_key udpv6_encap_needed __read_mostly;
 void udpv6_encap_enable(void)
 {
-	if (!static_key_enabled(&udpv6_encap_needed))
-		static_key_slow_inc(&udpv6_encap_needed);
+	static_key_enable(&udpv6_encap_needed);
 }
 EXPORT_SYMBOL(udpv6_encap_enable);
 
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 99c753c485ee..01130392b7c0 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -98,19 +98,26 @@ static struct conntrack_gc_work conntrack_gc_work;
 
 void nf_conntrack_lock(spinlock_t *lock) __acquires(lock)
 {
+	/* 1) Acquire the lock */
 	spin_lock(lock);
-	while (unlikely(nf_conntrack_locks_all)) {
-		spin_unlock(lock);
 
-		/*
-		 * Order the 'nf_conntrack_locks_all' load vs. the
-		 * spin_unlock_wait() loads below, to ensure
-		 * that 'nf_conntrack_locks_all_lock' is indeed held:
-		 */
-		smp_rmb(); /* spin_lock(&nf_conntrack_locks_all_lock) */
-		spin_unlock_wait(&nf_conntrack_locks_all_lock);
-		spin_lock(lock);
-	}
+	/* 2) read nf_conntrack_locks_all, with ACQUIRE semantics
+	 * It pairs with the smp_store_release() in nf_conntrack_all_unlock()
+	 */
+	if (likely(smp_load_acquire(&nf_conntrack_locks_all) == false))
+		return;
+
+	/* fast path failed, unlock */
+	spin_unlock(lock);
+
+	/* Slow path 1) get global lock */
+	spin_lock(&nf_conntrack_locks_all_lock);
+
+	/* Slow path 2) get the lock we want */
+	spin_lock(lock);
+
+	/* Slow path 3) release the global lock */
+	spin_unlock(&nf_conntrack_locks_all_lock);
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_lock);
 
@@ -151,28 +158,27 @@ static void nf_conntrack_all_lock(void)
 	int i;
 
 	spin_lock(&nf_conntrack_locks_all_lock);
-	nf_conntrack_locks_all = true;
 
-	/*
-	 * Order the above store of 'nf_conntrack_locks_all' against
-	 * the spin_unlock_wait() loads below, such that if
-	 * nf_conntrack_lock() observes 'nf_conntrack_locks_all'
-	 * we must observe nf_conntrack_locks[] held:
-	 */
-	smp_mb(); /* spin_lock(&nf_conntrack_locks_all_lock) */
+	nf_conntrack_locks_all = true;
 
 	for (i = 0; i < CONNTRACK_LOCKS; i++) {
-		spin_unlock_wait(&nf_conntrack_locks[i]);
+		spin_lock(&nf_conntrack_locks[i]);
+
+		/* This spin_unlock provides the "release" to ensure that
+		 * nf_conntrack_locks_all==true is visible to everyone that
+		 * acquired spin_lock(&nf_conntrack_locks[]).
+		 */
+		spin_unlock(&nf_conntrack_locks[i]);
 	}
 }
 
 static void nf_conntrack_all_unlock(void)
 {
-	/*
-	 * All prior stores must be complete before we clear
+	/* All prior stores must be complete before we clear
 	 * 'nf_conntrack_locks_all'. Otherwise nf_conntrack_lock()
 	 * might observe the false value but not the entire
-	 * critical section:
+	 * critical section.
+	 * It pairs with the smp_load_acquire() in nf_conntrack_lock()
 	 */
 	smp_store_release(&nf_conntrack_locks_all, false);
 	spin_unlock(&nf_conntrack_locks_all_lock);