From 3fbb27b7f87e60324cec7d2d10a40884182c99d4 Mon Sep 17 00:00:00 2001 From: "Matthieu Baerts (NGI0)" Date: Fri, 15 Nov 2024 17:52:34 +0100 Subject: mptcp: pm: lockless list traversal to dump endp To return an endpoint to the userspace via Netlink, and to dump all of them, the endpoint list was iterated while holding the pernet->lock, but only to read the content of the list. In these cases, the spin locks can be replaced by RCU read ones, and use the _rcu variants to iterate over the entries list in a lockless way. Note that the __lookup_addr_by_id() helper has been modified to use the _rcu variants of list_for_each_entry(), but with an extra conditions, so it can be called either while the RCU read lock is held, or when the associated pernet->lock is held. Reviewed-by: Geliang Tang Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20241115-net-next-mptcp-pm-lockless-dump-v1-1-f4a1bcb4ca2c@kernel.org Signed-off-by: Jakub Kicinski --- net/mptcp/pm_netlink.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) (limited to 'net/mptcp') diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 758a0dbfcf78..2b005ddfd2d3 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -512,7 +512,8 @@ __lookup_addr_by_id(struct pm_nl_pernet *pernet, unsigned int id) { struct mptcp_pm_addr_entry *entry; - list_for_each_entry(entry, &pernet->local_addr_list, list) { + list_for_each_entry_rcu(entry, &pernet->local_addr_list, list, + lockdep_is_held(&pernet->lock)) { if (entry->addr.id == id) return entry; } @@ -1824,7 +1825,7 @@ int mptcp_pm_nl_get_addr(struct sk_buff *skb, struct genl_info *info) goto fail; } - spin_lock_bh(&pernet->lock); + rcu_read_lock(); entry = __lookup_addr_by_id(pernet, addr.addr.id); if (!entry) { GENL_SET_ERR_MSG(info, "address not found"); @@ -1838,11 +1839,11 @@ int mptcp_pm_nl_get_addr(struct sk_buff *skb, struct genl_info *info) genlmsg_end(msg, reply); ret = genlmsg_reply(msg, info); - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); return ret; unlock_fail: - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); fail: nlmsg_free(msg); @@ -1866,7 +1867,7 @@ int mptcp_pm_nl_dump_addr(struct sk_buff *msg, pernet = pm_nl_get_pernet(net); - spin_lock_bh(&pernet->lock); + rcu_read_lock(); for (i = id; i < MPTCP_PM_MAX_ADDR_ID + 1; i++) { if (test_bit(i, pernet->id_bitmap)) { entry = __lookup_addr_by_id(pernet, i); @@ -1891,7 +1892,7 @@ int mptcp_pm_nl_dump_addr(struct sk_buff *msg, genlmsg_end(msg, hdr); } } - spin_unlock_bh(&pernet->lock); + rcu_read_unlock(); cb->args[0] = id; return msg->len; -- cgit