Commit a73e4195 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by David S. Miller
Browse files

ipv6: Add rt6_make_pcpu_route() 



It is a prep work for fixing a potential deadlock when creating
a pcpu rt.

The current rt6_get_pcpu_route() will also create a pcpu rt if one does not
exist.  This patch moves the pcpu rt creation logic into another function,
rt6_make_pcpu_route().

Signed-off-by: default avatarMartin KaFai Lau <kafai@fb.com>
CC: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ad706862

net/ipv6/route.c

+16 −4
Original line number Diff line number Diff line
@@ -993,13 +993,21 @@ static struct rt6_info *ip6_rt_pcpu_alloc(struct rt6_info *rt) 
/* It should be called with read_lock_bh(&tb6_lock) acquired */

static struct rt6_info *rt6_get_pcpu_route(struct rt6_info *rt)

{

	struct rt6_info *pcpu_rt, *prev, **p;

	struct rt6_info *pcpu_rt, **p;



	p = this_cpu_ptr(rt->rt6i_pcpu);

	pcpu_rt = *p;



	if (pcpu_rt)

		goto done;

	if (pcpu_rt) {

		dst_hold(&pcpu_rt->dst);

		rt6_dst_from_metrics_check(pcpu_rt);

	}

	return pcpu_rt;

}



static struct rt6_info *rt6_make_pcpu_route(struct rt6_info *rt)

{

	struct rt6_info *pcpu_rt, *prev, **p;



	pcpu_rt = ip6_rt_pcpu_alloc(rt);

	if (!pcpu_rt) {
@@ -1009,6 +1017,7 @@ static struct rt6_info *rt6_get_pcpu_route(struct rt6_info *rt) 
		goto done;

	}



	p = this_cpu_ptr(rt->rt6i_pcpu);

	prev = cmpxchg(p, NULL, pcpu_rt);

	if (prev) {

		/* If someone did it before us, return prev instead */
@@ -1093,8 +1102,11 @@ redo_rt6_select: 
		rt->dst.lastuse = jiffies;

		rt->dst.__use++;

		pcpu_rt = rt6_get_pcpu_route(rt);

		read_unlock_bh(&table->tb6_lock);



		if (!pcpu_rt)

			pcpu_rt = rt6_make_pcpu_route(rt);



		read_unlock_bh(&table->tb6_lock);

		return pcpu_rt;

	}

}

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