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ipv6: Add rt6_make_pcpu_route()

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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: Martin KaFai Lau <kafai@fb.com>
CC: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Martin KaFai Lau 2015-08-14 11:05:53 -07:00 committed by David S. Miller
parent ad70686289
commit a73e419563
1 changed files with 16 additions and 4 deletions
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20
net/ipv6/route.c
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@ -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;
}
}