linux-kernel - [PATCH 2/3] jump_labels: do not use unserialized static_key

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Message-Id: <1501601046-35683-3-git-send-email-pbonzini@redhat.com>
Date:   Tue,  1 Aug 2017 17:24:05 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH 2/3] jump_labels: do not use unserialized static_key_enabled

Any use of key->enabled (that is static_key_enabled and static_key_count)
outside jump_label_lock should handle its own serialization.  The only
two that are not doing so are the UDP encapsulation static keys.  Change
them to use static_key_enable, which now correctly tests key->enabled under
the jump label lock.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 Documentation/static-keys.txt | 5 +++++
 net/ipv4/udp.c                | 3 +--
 net/ipv6/udp.c                | 3 +--
 3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/static-keys.txt b/Documentation/static-keys.txt
index ef419fd0897f..181998852961 100644
--- a/Documentation/static-keys.txt
+++ b/Documentation/static-keys.txt
@@ -142,6 +142,11 @@ static_branch_inc(), will change the branch back to true. Likewise, if the
 key is initialized false, a 'static_branch_inc()', will change the branch to
 true. And then a 'static_branch_dec()', will again make the branch false.
 
+The state and the reference count can be retrieved with 'static_key_enabled()'
+and 'static_key_count()'.  In general, if you use these functions, they
+should be protected with the same mutex used around the enable/disable
+or increment/decrement function.
+
 Where an array of keys is required, it can be defined as:
 
 	DEFINE_STATIC_KEY_ARRAY_TRUE(keys, count);
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 1d6219bf2d6b..74b7810df9fc 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1644,8 +1644,7 @@ 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 75703fda23e7..1a96233622b7 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -564,8 +564,7 @@ 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);
 
-- 
1.8.3.1