From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexei Starovoitov Subject: [PATCH net-next] net_sched: act_bpf: remove spinlock in fast path Date: Mon, 3 Aug 2015 22:09:12 -0700 Message-ID: <1438664952-24712-1-git-send-email-ast@plumgrid.com> Cc: Eric Dumazet , Daniel Borkmann , Jiri Pirko , netdev@vger.kernel.org To: "David S. Miller" Return-path: Received: from mail-pa0-f43.google.com ([209.85.220.43]:36834 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750956AbbHDFJU (ORCPT ); Tue, 4 Aug 2015 01:09:20 -0400 Received: by pacgq8 with SMTP id gq8so41511491pac.3 for ; Mon, 03 Aug 2015 22:09:19 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: Similar to act_gact/act_mirred, act_bpf can be lockless in packet processing. Also similar to gact/mirred there is a race between prog->filter and prog->tcf_action. Meaning that the program being replaced may use previous default action if it happened to return TC_ACT_UNSPEC. act_mirred race betwen tcf_action and tcfm_dev is similar. In all cases the race is harmless. Long term we may want to improve the situation by replacing the whole struct tc_action as single pointer instead of updating inner fields one by one. Signed-off-by: Alexei Starovoitov --- net/sched/act_bpf.c | 15 +++++---------- 1 file changed, 5 insertions(+), 10 deletions(-) diff --git a/net/sched/act_bpf.c b/net/sched/act_bpf.c index 1b97dabc621a..2b8c47200152 100644 --- a/net/sched/act_bpf.c +++ b/net/sched/act_bpf.c @@ -43,10 +43,8 @@ static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act, if (unlikely(!skb_mac_header_was_set(skb))) return TC_ACT_UNSPEC; - spin_lock(&prog->tcf_lock); - - prog->tcf_tm.lastuse = jiffies; - bstats_update(&prog->tcf_bstats, skb); + tcf_lastuse_update(&prog->tcf_tm); + bstats_cpu_update(this_cpu_ptr(prog->common.cpu_bstats), skb); /* Needed here for accessing maps. */ rcu_read_lock(); @@ -77,7 +75,7 @@ static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act, break; case TC_ACT_SHOT: action = filter_res; - prog->tcf_qstats.drops++; + qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats)); break; case TC_ACT_UNSPEC: action = prog->tcf_action; @@ -87,7 +85,6 @@ static int tcf_bpf(struct sk_buff *skb, const struct tc_action *act, break; } - spin_unlock(&prog->tcf_lock); return action; } @@ -294,7 +291,7 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla, if (!tcf_hash_check(parm->index, act, bind)) { ret = tcf_hash_create(parm->index, est, act, - sizeof(*prog), bind, false); + sizeof(*prog), bind, true); if (ret < 0) return ret; @@ -325,7 +322,7 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla, goto out; prog = to_bpf(act); - spin_lock_bh(&prog->tcf_lock); + ASSERT_RTNL(); if (ret != ACT_P_CREATED) tcf_bpf_prog_fill_cfg(prog, &old); @@ -341,8 +338,6 @@ static int tcf_bpf_init(struct net *net, struct nlattr *nla, prog->tcf_action = parm->action; prog->filter = cfg.filter; - spin_unlock_bh(&prog->tcf_lock); - if (res == ACT_P_CREATED) tcf_hash_insert(act); else -- 1.7.9.5