linux-kernel - Re: [PATCH] Code clean up for percpu

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Date:	Thu, 20 Oct 2011 14:04:27 +0800
From:	"Alex,Shi" <alex.shi@...el.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Christoph Lameter <cl@...two.org>, "tj@...nel.org" <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Huang, Ying" <ying.huang@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"avi@...hat.com" <avi@...hat.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"jeremy@...source.com" <jeremy@...source.com>
Subject: Re: [PATCH] Code clean up for percpu_xxx() functions


> Sorry this huge patch brings too many potential bugs.
> 
> I ask you a separate patch for the networking part, because I dont want
> to Ack all the other parts.
> 

Thanks a lot for review! I split the first patch into 2 according your
suggestion. The second one for network here: 

>>From d5d71127ad22890f6f13fa382736c0df7f5d0231 Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@...el.com>
Date: Thu, 20 Oct 2011 13:44:37 +0800
Subject: [PATCH 2/2] change this_cpu_xxx funcs for preempt safe scenarios

If context is preempt safe, using __this_cpu_xxx to replace this_cpu_xxx
have performance benefit, since the later has a abundant preempt_disable
instruction.

Signed-off-by: Alex Shi <alex.shi@...el.com>
---
 net/netfilter/xt_TEE.c |   12 ++++++------
 1 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/netfilter/xt_TEE.c b/net/netfilter/xt_TEE.c
index e78103d..678084c 100644
--- a/net/netfilter/xt_TEE.c
+++ b/net/netfilter/xt_TEE.c
@@ -90,7 +90,7 @@ tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 	const struct xt_tee_tginfo *info = par->targinfo;
 	struct iphdr *iph;
 
-	if (this_cpu_read(tee_active))
+	if (__this_cpu_read(tee_active))
 		return XT_CONTINUE;
 	/*
 	 * Copy the skb, and route the copy. Will later return %XT_CONTINUE for
@@ -127,9 +127,9 @@ tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 	ip_send_check(iph);
 
 	if (tee_tg_route4(skb, info)) {
-		this_cpu_write(tee_active, true);
+		__this_cpu_write(tee_active, true);
 		ip_local_out(skb);
-		this_cpu_write(tee_active, false);
+		__this_cpu_write(tee_active, false);
 	} else {
 		kfree_skb(skb);
 	}
@@ -170,7 +170,7 @@ tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 {
 	const struct xt_tee_tginfo *info = par->targinfo;
 
-	if (this_cpu_read(tee_active))
+	if (__this_cpu_read(tee_active))
 		return XT_CONTINUE;
 	skb = pskb_copy(skb, GFP_ATOMIC);
 	if (skb == NULL)
@@ -188,9 +188,9 @@ tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 		--iph->hop_limit;
 	}
 	if (tee_tg_route6(skb, info)) {
-		this_cpu_write(tee_active, true);
+		__this_cpu_write(tee_active, true);
 		ip6_local_out(skb);
-		this_cpu_write(tee_active, false);
+		__this_cpu_write(tee_active, false);
 	} else {
 		kfree_skb(skb);
 	}
-- 
1.6.3.3



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