mirror of https://github.com/torvalds/linux.git
3765996e4f
The process will cause napi.state to contain NAPI_STATE_SCHED and
not in the poll_list, which will cause napi_disable() to get stuck.
The prefix "NAPI_STATE_" is removed in the figure below, and
NAPI_STATE_HASHED is ignored in napi.state.
CPU0 | CPU1 | napi.state
===============================================================================
napi_disable() | | SCHED | NPSVC
napi_enable() | |
{ | |
smp_mb__before_atomic(); | |
clear_bit(SCHED, &n->state); | | NPSVC
| napi_schedule_prep() | SCHED | NPSVC
| napi_poll() |
| napi_complete_done() |
| { |
| if (n->state & (NPSVC | | (1)
| _BUSY_POLL))) |
| return false; |
| ................ |
| } | SCHED | NPSVC
| |
clear_bit(NPSVC, &n->state); | | SCHED
} | |
| |
napi_schedule_prep() | | SCHED | MISSED (2)
(1) Here return direct. Because of NAPI_STATE_NPSVC exists.
(2) NAPI_STATE_SCHED exists. So not add napi.poll_list to sd->poll_list
Since NAPI_STATE_SCHED already exists and napi is not in the
sd->poll_list queue, NAPI_STATE_SCHED cannot be cleared and will always
exist.
1. This will cause this queue to no longer receive packets.
2. If you encounter napi_disable under the protection of rtnl_lock, it
will cause the entire rtnl_lock to be locked, affecting the overall
system.
This patch uses cmpxchg to implement napi_enable(), which ensures that
there will be no race due to the separation of clear two bits.
Fixes:
|
||
|---|---|---|
| .. | ||
| Makefile | ||
| bpf_sk_storage.c | ||
| datagram.c | ||
| datagram.h | ||
| dev.c | ||
| dev_addr_lists.c | ||
| dev_ioctl.c | ||
| devlink.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_cells.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 | ||
| netevent.c | ||
| netpoll.c | ||
| netprio_cgroup.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_diag.c | ||
| sock_map.c | ||
| sock_reuseport.c | ||
| stream.c | ||
| sysctl_net_core.c | ||
| timestamping.c | ||
| tso.c | ||
| utils.c | ||
| xdp.c | ||