From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:34715 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754150AbbLKUWG (ORCPT ); Fri, 11 Dec 2015 15:22:06 -0500 Subject: Patch "ip_tunnel: disable preemption when updating per-cpu tstats" has been added to the 4.2-stable tree To: Jason@zx2c4.com, davem@davemloft.net, gregkh@linuxfoundation.org, hannes@stressinduktion.org Cc: , From: Date: Fri, 11 Dec 2015 08:49:04 -0800 Message-ID: <144985254425524@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled ip_tunnel: disable preemption when updating per-cpu tstats to the 4.2-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ip_tunnel-disable-preemption-when-updating-per-cpu-tstats.patch and it can be found in the queue-4.2 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From foo@baz Fri Dec 11 11:38:35 EST 2015 From: "Jason A. Donenfeld" Date: Thu, 12 Nov 2015 17:35:58 +0100 Subject: ip_tunnel: disable preemption when updating per-cpu tstats From: "Jason A. Donenfeld" [ Upstream commit b4fe85f9c9146f60457e9512fb6055e69e6a7a65 ] 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] [] dump_stack+0x4f/0x7b [ 188.435615] [] check_preemption_disabled+0x19d/0x1c0 [ 188.435619] [] 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 Acked-by: Hannes Frederic Sowa Signed-off-by: David S. Miller Signed-off-by: Greg Kroah-Hartman --- include/net/ip6_tunnel.h | 3 ++- include/net/ip_tunnels.h | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) --- a/include/net/ip6_tunnel.h +++ b/include/net/ip6_tunnel.h @@ -83,11 +83,12 @@ static inline void ip6tunnel_xmit(struct err = ip6_local_out_sk(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++; --- a/include/net/ip_tunnels.h +++ b/include/net/ip_tunnels.h @@ -207,12 +207,13 @@ static inline void iptunnel_xmit_stats(i struct pcpu_sw_netstats __percpu *stats) { if (err > 0) { - struct pcpu_sw_netstats *tstats = this_cpu_ptr(stats); + struct pcpu_sw_netstats *tstats = get_cpu_ptr(stats); u64_stats_update_begin(&tstats->syncp); tstats->tx_bytes += err; tstats->tx_packets++; u64_stats_update_end(&tstats->syncp); + put_cpu_ptr(tstats); } else if (err < 0) { err_stats->tx_errors++; err_stats->tx_aborted_errors++; Patches currently in stable-queue which might be from Jason@zx2c4.com are queue-4.2/ip_tunnel-disable-preemption-when-updating-per-cpu-tstats.patch