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

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  [PATCH 2/3] jump_labels: do not use unserialized static_key_enabled Paolo Bonzini <pbonzini@redhat.com> - 2017-08-01 17:30 +0200
    Re: [PATCH 2/3] jump_labels: do not use unserialized  static_key_enabled Eric Dumazet <eric.dumazet@gmail.com> - 2017-08-01 23:00 +0200
      Re: [PATCH 2/3] jump_labels: do not use unserialized  static_key_enabled Paolo Bonzini <pbonzini@redhat.com> - 2017-08-02 07:50 +0200
    [tip:locking/core] jump_label: Do not use unserialized  static_key_enabled() tip-bot for Paolo Bonzini <tipbot@zytor.com> - 2017-08-10 14:20 +0200

#1701156 — [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@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.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

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#1701484 — Re: [PATCH 2/3] jump_labels: do not use unserialized static_key_enabled

On Tue, 2017-08-01 at 17:24 +0200, Paolo Bonzini wrote:
> 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@infradead.org>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.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);
>  }

Looks good to me, but static_key_enable() is not serialized either ?

I suspect you should have CCed me on patch 1/3 :)

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#1701734 — Re: [PATCH 2/3] jump_labels: do not use unserialized static_key_enabled

----- Original Message -----
> From: "Eric Dumazet" <eric.dumazet@gmail.com>
> To: "Paolo Bonzini" <pbonzini@redhat.com>
> Cc: linux-kernel@vger.kernel.org, "Peter Zijlstra" <peterz@infradead.org>
> Sent: Tuesday, August 1, 2017 10:52:14 PM
> Subject: Re: [PATCH 2/3] jump_labels: do not use unserialized static_key_enabled
> 
> On Tue, 2017-08-01 at 17:24 +0200, Paolo Bonzini wrote:
> > 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.
> >
> > 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);
> >  }
> 
> Looks good to me, but static_key_enable() is not serialized either ?
> 
> I suspect you should have CCed me on patch 1/3 :)

Yes, indeed...  That's the "now correctly test" in the commit message.
What a difference one word makes. :)

You can find 1/3 at https://patchwork.kernel.org/patch/9874845/.

Paolo

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#1708532 — [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@redhat.com>
AuthorDate: Tue, 1 Aug 2017 17:24:05 +0200
Committer:  Ingo Molnar <mingo@kernel.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@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1501601046-35683-3-git-send-email-pbonzini@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.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);
 

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