linux-kernel - [tip:locking/core] jump_label: Do not use unserialized static_key

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Date:   Thu, 10 Aug 2017 05:12:52 -0700
From:   tip-bot for Paolo Bonzini <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, pbonzini@...hat.com,
        linux-kernel@...r.kernel.org, jbaron@...mai.com, mingo@...nel.org,
        eric.dumazet@...il.com, torvalds@...ux-foundation.org,
        peterz@...radead.org, hpa@...or.com
Subject: [tip:locking/core] jump_label: Do not use unserialized
 static_key_enabled()

Commit-ID:  7a34bcb8b272b1300f0125c93a54f0c98812acdd
Gitweb:     http://git.kernel.org/tip/7a34bcb8b272b1300f0125c93a54f0c98812acdd
Author:     Paolo Bonzini <pbonzini@...hat.com>
AuthorDate: Tue, 1 Aug 2017 17:24:05 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 10 Aug 2017 12:28:56 +0200

jump_label: 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.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Jason Baron <jbaron@...mai.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1501601046-35683-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 b83dfa1..870b4be 100644
--- a/Documentation/static-keys.txt
+++ b/Documentation/static-keys.txt
@@ -149,6 +149,11 @@ 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 e6276fa..3037339 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1809,8 +1809,7 @@ 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 578142b..96d2407 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -574,8 +574,7 @@ 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);