linux-kernel - Re: [PATCH 3/3] udp: make use of static_key_slow_set

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Date:	Mon, 01 Jul 2013 00:20:32 -0400
From:	Jason Baron <jbaron@...mai.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	"andi@...stfloor.org" <andi@...stfloor.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH 3/3] udp: make use of static_key_slow_set_true() interface

On 06/28/2013 11:13 PM, Steven Rostedt wrote:
> On Fri, 2013-06-28 at 22:30 +0000, jbaron@...mai.com wrote:
>> Make use of the simpler API.
> Need to make the change log much more descriptive. Never assume someone
> in the future that looks up a change to this file will know about other
> commits that led to this. Each change log should be sufficient to stand
> on its own.
>
> Explain why this patch is needed. And it's not about the use of a
> simpler API.
>
> It actually fixes a real bug.
>
>
>> Signed-off-by: Jason Baron <jbaron@...mai.com>
>> ---
>>   net/ipv4/udp.c |    9 ++++-----
>>   net/ipv6/udp.c |    9 ++++-----
>>   2 files changed, 8 insertions(+), 10 deletions(-)
>>
>> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
>> index 0bf5d39..b8d0029 100644
>> --- a/net/ipv4/udp.c
>> +++ b/net/ipv4/udp.c
>> @@ -1421,11 +1421,10 @@ static int __udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
>>   
>>   }
>>   
>> -static struct static_key udp_encap_needed __read_mostly;
>> +static struct static_key_boolean 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_slow_set_true(&udp_encap_needed);
>>   }
>>   EXPORT_SYMBOL(udp_encap_enable);
>>   
>> @@ -1450,7 +1449,7 @@ int udp_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
>>   		goto drop;
>>   	nf_reset(skb);
>>   
>> -	if (static_key_false(&udp_encap_needed) && up->encap_type) {
>> +	if (static_key_false(&udp_encap_needed.key) && up->encap_type) {
> I wonder if we should add a static_bool_key_false(), because that added
> ".key" is a bit confusing.
>
> -- Steve
>

Yeah - that is sort of ugly, but it avoids introducing a new branch API 
call. That said, a 'static_bool_key_false()' would probably be a simple 
wrapper function.

-Jason


>>   		int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
>>   
>>   		/*
>> @@ -1773,7 +1772,7 @@ void udp_destroy_sock(struct sock *sk)
>>   	bool slow = lock_sock_fast(sk);
>>   	udp_flush_pending_frames(sk);
>>   	unlock_sock_fast(sk, slow);
>> -	if (static_key_false(&udp_encap_needed) && up->encap_type) {
>> +	if (static_key_false(&udp_encap_needed.key) && up->encap_type) {
>>   		void (*encap_destroy)(struct sock *sk);
>>   		encap_destroy = ACCESS_ONCE(up->encap_destroy);
>>   		if (encap_destroy)
>> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
>> index 42923b1..94a4091 100644
>> --- a/net/ipv6/udp.c
>> +++ b/net/ipv6/udp.c
>> @@ -573,11 +573,10 @@ static __inline__ void udpv6_err(struct sk_buff *skb,
>>   	__udp6_lib_err(skb, opt, type, code, offset, info, &udp_table);
>>   }
>>   
>> -static struct static_key udpv6_encap_needed __read_mostly;
>> +static struct static_key_boolean 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_slow_set_true(&udpv6_encap_needed);
>>   }
>>   EXPORT_SYMBOL(udpv6_encap_enable);
>>   
>> @@ -590,7 +589,7 @@ int udpv6_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
>>   	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
>>   		goto drop;
>>   
>> -	if (static_key_false(&udpv6_encap_needed) && up->encap_type) {
>> +	if (static_key_false(&udpv6_encap_needed.key) && up->encap_type) {
>>   		int (*encap_rcv)(struct sock *sk, struct sk_buff *skb);
>>   
>>   		/*
>> @@ -1300,7 +1299,7 @@ void udpv6_destroy_sock(struct sock *sk)
>>   	udp_v6_flush_pending_frames(sk);
>>   	release_sock(sk);
>>   
>> -	if (static_key_false(&udpv6_encap_needed) && up->encap_type) {
>> +	if (static_key_false(&udpv6_encap_needed.key) && up->encap_type) {
>>   		void (*encap_destroy)(struct sock *sk);
>>   		encap_destroy = ACCESS_ONCE(up->encap_destroy);
>>   		if (encap_destroy)
>

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