From: Oliver Herms <oliver.peter.herms@gmail•com>
To: netdev@vger•kernel.org
Cc: davem@davemloft•net, kuznet@ms2•inr.ac.ru,
yoshfuji@linux-ipv6•org, kuba@kernel•org
Subject: [PATCH] IPv6: Fix CPU contention on FIB6 GC
Date: Mon, 22 Jun 2020 22:53:55 +0200 [thread overview]
Message-ID: <20200622205355.GA869719@tws> (raw)
When fib6_run_gc is called with parameter force=true the spinlock in
/net/ipv6/ip6_fib.c:2310 can lock all CPUs in softirq when
net.ipv6.route.max_size is exceeded (seen this multiple times).
One sotirq/CPU get's the lock. All others spin to get it. It takes
substantial time until all are done. Effectively it's a DOS vector.
As the splinlock is only enforcing that there is at most one GC running
at a time, it should IMHO be safe to use force=false here resulting
in spin_trylock_bh instead of spin_lock_bh, thus avoiding the lock
contention.
Finding a locked spinlock means some GC is going on already so it is
save to just skip another execution of the GC.
Signed-off-by: Oliver Herms <oliver.peter.herms@gmail•com>
---
net/ipv6/route.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 82cbb46a2a4f..7e6fbaf43549 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3205,7 +3205,7 @@ static int ip6_dst_gc(struct dst_ops *ops)
goto out;
net->ipv6.ip6_rt_gc_expire++;
- fib6_run_gc(net->ipv6.ip6_rt_gc_expire, net, true);
+ fib6_run_gc(net->ipv6.ip6_rt_gc_expire, net, false);
entries = dst_entries_get_slow(ops);
if (entries < ops->gc_thresh)
net->ipv6.ip6_rt_gc_expire = rt_gc_timeout>>1;
--
2.25.1
next reply other threads:[~2020-06-22 20:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 20:53 Oliver Herms [this message]
2020-06-22 21:44 ` [PATCH] IPv6: Fix CPU contention on FIB6 GC Michal Kubecek
2020-06-22 22:46 ` Oliver Herms
2020-06-23 21:56 ` Michal Kubecek
2020-06-22 22:55 ` Eric Dumazet
2020-06-22 23:30 ` Oliver Herms
2020-06-23 22:06 ` Michal Kubecek
2020-06-24 10:34 ` Oliver Herms
2020-06-24 16:42 ` Eric Dumazet
2020-06-25 8:02 ` Oliver Herms
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