netdev - [PATCH net-next] net: sched: don't release block->lock when dumping chains

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20190225154544.10453-1-vladbu@mellanox.com>
Date:   Mon, 25 Feb 2019 17:45:44 +0200
From:   Vlad Buslov <vladbu@...lanox.com>
To:     netdev@...r.kernel.org
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, Vlad Buslov <vladbu@...lanox.com>
Subject: [PATCH net-next] net: sched: don't release block->lock when dumping chains

Function tc_dump_chain() obtains and releases block->lock on each iteration
of its inner loop that dumps all chains on block. Outputting chain template
info is fast operation so locking/unlocking mutex multiple times is an
overhead when lock is highly contested. Modify tc_dump_chain() to only
obtain block->lock once and dump all chains without releasing it.

Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
Suggested-by: Cong Wang <xiyou.wangcong@...il.com>
---
 net/sched/cls_api.c | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 3543be31d400..5c6a9baa389f 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -2996,12 +2996,12 @@ static int tc_ctl_chain(struct sk_buff *skb, struct nlmsghdr *n,
 /* called with RTNL */
 static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
 {
-	struct tcf_chain *chain, *chain_prev;
 	struct net *net = sock_net(skb->sk);
 	struct nlattr *tca[TCA_MAX + 1];
 	struct Qdisc *q = NULL;
 	struct tcf_block *block;
 	struct tcmsg *tcm = nlmsg_data(cb->nlh);
+	struct tcf_chain *chain;
 	long index_start;
 	long index;
 	u32 parent;
@@ -3064,11 +3064,8 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
 	index_start = cb->args[0];
 	index = 0;
 
-	for (chain = __tcf_get_next_chain(block, NULL);
-	     chain;
-	     chain_prev = chain,
-		     chain = __tcf_get_next_chain(block, chain),
-		     tcf_chain_put(chain_prev)) {
+	mutex_lock(&block->lock);
+	list_for_each_entry(chain, &block->chain_list, list) {
 		if ((tca[TCA_CHAIN] &&
 		     nla_get_u32(tca[TCA_CHAIN]) != chain->index))
 			continue;
@@ -3076,17 +3073,18 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
 			index++;
 			continue;
 		}
+		if (tcf_chain_held_by_acts_only(chain))
+			continue;
 		err = tc_chain_fill_node(chain->tmplt_ops, chain->tmplt_priv,
 					 chain->index, net, skb, block,
 					 NETLINK_CB(cb->skb).portid,
 					 cb->nlh->nlmsg_seq, NLM_F_MULTI,
 					 RTM_NEWCHAIN);
-		if (err <= 0) {
-			tcf_chain_put(chain);
+		if (err <= 0)
 			break;
-		}
 		index++;
 	}
+	mutex_unlock(&block->lock);
 
 	if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK)
 		tcf_block_refcnt_put(block, true);
-- 
2.13.6