7a44f4944b
[ Upstream commit cd42ba1c8ac9deb9032add6adf491110e7442040 ]
This came while reviewing commit c4e86b4363ac ("net: add two more
call_rcu_hurry()").
Paolo asked if adding one synchronize_rcu() would help.
While synchronize_rcu() does not help, making sure to call
rcu_barrier() before msleep(wait) is definitely helping
to make sure lazy call_rcu() are completed.
Instead of waiting ~100 seconds in my tests, the ref_tracker
splats occurs one time only, and netdev_wait_allrefs_any()
latency is reduced to the strict minimum.
Ideally we should audit our call_rcu() users to make sure
no refcount (or cascading call_rcu()) is held too long,
because rcu_barrier() is quite expensive.
Fixes:
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|---|---|---|
| .. | ||
| Makefile | ||
| bpf_sk_storage.c | ||
| datagram.c | ||
| dev.c | ||
| dev.h | ||
| dev_addr_lists.c | ||
| dev_addr_lists_test.c | ||
| dev_ioctl.c | ||
| drop_monitor.c | ||
| dst.c | ||
| dst_cache.c | ||
| failover.c | ||
| fib_notifier.c | ||
| fib_rules.c | ||
| filter.c | ||
| flow_dissector.c | ||
| flow_offload.c | ||
| gen_estimator.c | ||
| gen_stats.c | ||
| gro.c | ||
| gro_cells.c | ||
| gso.c | ||
| hwbm.c | ||
| link_watch.c | ||
| lwt_bpf.c | ||
| lwtunnel.c | ||
| neighbour.c | ||
| net-procfs.c | ||
| net-sysfs.c | ||
| net-sysfs.h | ||
| net-traces.c | ||
| net_namespace.c | ||
| netclassid_cgroup.c | ||
| netdev-genl-gen.c | ||
| netdev-genl-gen.h | ||
| netdev-genl.c | ||
| netevent.c | ||
| netpoll.c | ||
| netprio_cgroup.c | ||
| of_net.c | ||
| page_pool.c | ||
| pktgen.c | ||
| ptp_classifier.c | ||
| request_sock.c | ||
| rtnetlink.c | ||
| scm.c | ||
| secure_seq.c | ||
| selftests.c | ||
| skbuff.c | ||
| skmsg.c | ||
| sock.c | ||
| sock_destructor.h | ||
| sock_diag.c | ||
| sock_map.c | ||
| sock_reuseport.c | ||
| stream.c | ||
| sysctl_net_core.c | ||
| timestamping.c | ||
| tso.c | ||
| utils.c | ||
| xdp.c | ||