[PATCH 2/3] jump_labels: do not use unserialized static_key_enabled

From: Paolo Bonzini
Date: Tue Aug 01 2017 - 11:24:53 EST

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@xxxxxxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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:

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);

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);