From 650c21d9d35b76960f9285c589d9919bcf3818b5 Mon Sep 17 00:00:00 2001 From: David Marchand Date: Wed, 18 Oct 2023 16:23:53 +0200 Subject: [PATCH] ofproto-dpif-upcall: Pause revalidators when purging. This issue has been observed when running traffic tests with a dpdk enabled userspace datapath (though those tests are added in a separate series). However, the described issue also affects the kernel datapath which is why this patch is sent separately. A main thread executing the 'revalidator/purge' command could race with revalidator threads that can be dumping/sweeping the purged flows at the same time. This race can be reproduced (with dpif debug logs) by running the conntrack - ICMP related unit tests with the userspace datapath: 2023-10-09T14:11:55.242Z|00177|unixctl|DBG|received request revalidator/purge[], id=0 2023-10-09T14:11:55.242Z|00044|dpif(revalidator17)|DBG|netdev@ovs-netdev: flow_dump ufid:68ff6817-fb3b-4b30-8412-9cf175318294 , packets:0, bytes:0, used:never 2023-10-09T14:11:55.242Z|00178|dpif|DBG|netdev@ovs-netdev: flow_del ufid:07046e91-30a6-4862-9048-1a76b5a88a5b recirc_id(0),dp_hash(0),skb_priority(0),in_port(2),skb_mark(0), ct_state(0),ct_zone(0),ct_mark(0),ct_label(0), packet_type(ns=0,id=0), eth(src=a6:0a:bf:e2:f3:f2,dst=62:23:0f:f6:2c:75), eth_type(0x0800),ipv4(src=10.1.1.1,dst=10.1.1.2,proto=17,tos=0, ttl=64,frag=no),udp(src=37380,dst=10000), packets:0, bytes:0, used:never ... 2023-10-09T14:11:55.242Z|00049|dpif(revalidator17)|WARN|netdev@ovs-netdev: failed to flow_get (No such file or directory) ufid:07046e91-30a6-4862-9048-1a76b5a88a5b , packets:0, bytes:0, used:never 2023-10-09T14:11:55.242Z|00050|ofproto_dpif_upcall(revalidator17)|WARN| Failed to acquire udpif_key corresponding to unexpected flow (No such file or directory): ufid:07046e91-30a6-4862-9048-1a76b5a88a5b ... 2023-10-09T14:11:55.242Z|00183|unixctl|DBG|replying with success, id=0: "" To avoid this race, a first part of the fix is to pause (if not already paused) the revalidators while the main thread is purging the datapath flows. Then a second issue is observed by running the same unit test with the kernel datapath. Its dpif implementation dumps flows via a netlink request (see dpif_flow_dump_create(), dpif_netlink_flow_dump_create(), nl_dump_start(), nl_sock_send__()) in the leader revalidator thread, before pausing revalidators: 2023-10-09T14:44:28.742Z|00122|unixctl|DBG|received request revalidator/purge[], id=0 ... 2023-10-09T14:44:28.742Z|00125|dpif|DBG|system@ovs-system: flow_del ufid:70102d81-30a1-44b9-aa76-3d02a9ffd2c9 recirc_id(0),dp_hash(0), skb_priority(0),in_port(2),skb_mark(0),ct_state(0),ct_zone(0), ct_mark(0),ct_label(0),eth(src=a6:0a:bf:e2:f3:f2, dst=ff:ff:ff:ff:ff:ff),eth_type(0x0806),arp(sip=10.1.1.1, tip=10.1.1.2,op=1,sha=a6:0a:bf:e2:f3:f2,tha=00:00:00:00:00:00), packets:0, bytes:0, used:never ... 2023-10-09T14:44:28.742Z|00129|unixctl|DBG|replying with success, id=0: "" ... 2023-10-09T14:44:28.742Z|00006|dpif(revalidator21)|DBG|system@ovs-system: flow_dump ufid:70102d81-30a1-44b9-aa76-3d02a9ffd2c9 , packets:0, bytes:0, used:never ... 2023-10-09T14:44:28.742Z|00012|dpif(revalidator21)|WARN|system@ovs-system: failed to flow_get (No such file or directory) ufid:70102d81-30a1-44b9-aa76-3d02a9ffd2c9 , packets:0, bytes:0, used:never 2023-10-09T14:44:28.742Z|00013|ofproto_dpif_upcall(revalidator21)|WARN| Failed to acquire udpif_key corresponding to unexpected flow (No such file or directory): ufid:70102d81-30a1-44b9-aa76-3d02a9ffd2c9 To avoid evaluating already deleted flows, the second part of the fix is to ensure that dumping from the leader revalidator thread is done out of any pause request. As a result of this patch, the unit test "offloads - delete ufid mapping if device not exist - offloads enabled" does not need to waive the random warning logs when purging dp flows. Fixes: 98bb4286970d ("tests: Add command to purge revalidators of flows.") Acked-by: Eelco Chaudron Acked-by: Simon Horman Signed-off-by: David Marchand Signed-off-by: Ilya Maximets --- ofproto/ofproto-dpif-upcall.c | 17 +++++++++++++++-- tests/system-offloads-traffic.at | 2 -- 2 files changed, 15 insertions(+), 4 deletions(-) diff --git a/ofproto/ofproto-dpif-upcall.c b/ofproto/ofproto-dpif-upcall.c index 53b47073ad3..4629406b3f7 100644 --- a/ofproto/ofproto-dpif-upcall.c +++ b/ofproto/ofproto-dpif-upcall.c @@ -982,7 +982,7 @@ udpif_revalidator(void *arg) udpif->reval_exit = latch_is_set(&udpif->exit_latch); start_time = time_msec(); - if (!udpif->reval_exit) { + if (!udpif->reval_exit && !udpif->pause) { bool terse_dump; terse_dump = udpif_use_ufid(udpif); @@ -991,10 +991,15 @@ udpif_revalidator(void *arg) } } - /* Wait for the leader to start the flow dump. */ + /* Wait for the leader to reach this point. */ ovs_barrier_block(&udpif->reval_barrier); if (udpif->pause) { revalidator_pause(revalidator); + if (!udpif->reval_exit) { + /* The main thread resumed all validators, but the leader + * didn't start the dump, go to next iteration. */ + continue; + } } if (udpif->reval_exit) { @@ -3152,11 +3157,19 @@ upcall_unixctl_purge(struct unixctl_conn *conn, int argc OVS_UNUSED, struct udpif *udpif; LIST_FOR_EACH (udpif, list_node, &all_udpifs) { + bool wake_up = false; int n; + if (!latch_is_set(&udpif->pause_latch)) { + udpif_pause_revalidators(udpif); + wake_up = true; + } for (n = 0; n < udpif->n_revalidators; n++) { revalidator_purge(&udpif->revalidators[n]); } + if (wake_up) { + udpif_resume_revalidators(udpif); + } } unixctl_command_reply(conn, ""); } diff --git a/tests/system-offloads-traffic.at b/tests/system-offloads-traffic.at index 8dd3bdf8833..1d02ce6c0ee 100644 --- a/tests/system-offloads-traffic.at +++ b/tests/system-offloads-traffic.at @@ -851,8 +851,6 @@ AT_CHECK([test $(ovs-appctl dpctl/dump-flows | grep -c "eth_type(0x0800)") -eq 0 OVS_TRAFFIC_VSWITCHD_STOP(["/could not open network device ovs-p0/d /on nonexistent port/d -/failed to flow_get/d -/Failed to acquire udpif_key/d /No such device/d /failed to offload flow/d "])