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| author | Jason A. Donenfeld <Jason@zx2c4.com> | 2015-11-12 17:35:58 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-11-16 14:14:32 -0500 |
| commit | b4fe85f9c9146f60457e9512fb6055e69e6a7a65 (patch) | |
| tree | dfc8bcaffbc30be8c9d09c420a09c56ae895b70f /include/net/ip6_tunnel.h | |
| parent | 17c790a60dad11c0193127e83ac8e183b4fed1a2 (diff) | |
| download | lwn-b4fe85f9c9146f60457e9512fb6055e69e6a7a65.tar.gz lwn-b4fe85f9c9146f60457e9512fb6055e69e6a7a65.zip | |
ip_tunnel: disable preemption when updating per-cpu tstats
Drivers like vxlan use the recently introduced
udp_tunnel_xmit_skb/udp_tunnel6_xmit_skb APIs. udp_tunnel6_xmit_skb
makes use of ip6tunnel_xmit, and ip6tunnel_xmit, after sending the
packet, updates the struct stats using the usual
u64_stats_update_begin/end calls on this_cpu_ptr(dev->tstats).
udp_tunnel_xmit_skb makes use of iptunnel_xmit, which doesn't touch
tstats, so drivers like vxlan, immediately after, call
iptunnel_xmit_stats, which does the same thing - calls
u64_stats_update_begin/end on this_cpu_ptr(dev->tstats).
While vxlan is probably fine (I don't know?), calling a similar function
from, say, an unbound workqueue, on a fully preemptable kernel causes
real issues:
[ 188.434537] BUG: using smp_processor_id() in preemptible [00000000] code: kworker/u8:0/6
[ 188.435579] caller is debug_smp_processor_id+0x17/0x20
[ 188.435583] CPU: 0 PID: 6 Comm: kworker/u8:0 Not tainted 4.2.6 #2
[ 188.435607] Call Trace:
[ 188.435611] [<ffffffff8234e936>] dump_stack+0x4f/0x7b
[ 188.435615] [<ffffffff81915f3d>] check_preemption_disabled+0x19d/0x1c0
[ 188.435619] [<ffffffff81915f77>] debug_smp_processor_id+0x17/0x20
The solution would be to protect the whole
this_cpu_ptr(dev->tstats)/u64_stats_update_begin/end blocks with
disabling preemption and then reenabling it.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/ip6_tunnel.h')
| -rw-r--r-- | include/net/ip6_tunnel.h | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/include/net/ip6_tunnel.h b/include/net/ip6_tunnel.h index aaee6fa02cf1..ff788b665277 100644 --- a/include/net/ip6_tunnel.h +++ b/include/net/ip6_tunnel.h @@ -90,11 +90,12 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb, err = ip6_local_out(dev_net(skb_dst(skb)->dev), sk, skb); if (net_xmit_eval(err) == 0) { - struct pcpu_sw_netstats *tstats = this_cpu_ptr(dev->tstats); + struct pcpu_sw_netstats *tstats = get_cpu_ptr(dev->tstats); u64_stats_update_begin(&tstats->syncp); tstats->tx_bytes += pkt_len; tstats->tx_packets++; u64_stats_update_end(&tstats->syncp); + put_cpu_ptr(tstats); } else { stats->tx_errors++; stats->tx_aborted_errors++; |