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bpf, cpumask: Clean up bpf_cpu_map_entry directly in cpu_map_free

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After synchronous_rcu(), both the dettached XDP program and
xdp_do_flush() are completed, and the only user of bpf_cpu_map_entry
will be cpu_map_kthread_run(), so instead of calling
__cpu_map_entry_replace() to stop kthread and cleanup entry after a RCU
grace period, do these things directly.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20230816045959.358059-3-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Hou Tao 2023-08-16 12:59:58 +08:00 committed by Alexei Starovoitov
parent 8f8500a247
commit c2e42ddf26
1 changed files with 8 additions and 9 deletions
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17
kernel/bpf/cpumap.c
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@ -566,16 +566,15 @@ static void cpu_map_free(struct bpf_map *map)
/* At this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
* so the bpf programs (can be more than one that used this map) were
* disconnected from events. Wait for outstanding critical sections in
* these programs to complete. The rcu critical section only guarantees
* no further "XDP/bpf-side" reads against bpf_cpu_map->cpu_map.
* It does __not__ ensure pending flush operations (if any) are
* complete.
* these programs to complete. synchronize_rcu() below not only
* guarantees no further "XDP/bpf-side" reads against
* bpf_cpu_map->cpu_map, but also ensure pending flush operations
* (if any) are completed.
*/
synchronize_rcu();
/* For cpu_map the remote CPUs can still be using the entries
* (struct bpf_cpu_map_entry).
/* The only possible user of bpf_cpu_map_entry is
* cpu_map_kthread_run().
*/
for (i = 0; i < cmap->map.max_entries; i++) {
struct bpf_cpu_map_entry *rcpu;
@ -584,8 +583,8 @@ static void cpu_map_free(struct bpf_map *map)
if (!rcpu)
continue;
/* bq flush and cleanup happens after RCU grace-period */
__cpu_map_entry_replace(cmap, i, NULL); /* call_rcu */
/* Stop kthread and cleanup entry directly */
__cpu_map_entry_free(&rcpu->free_work.work);
}
bpf_map_area_free(cmap->cpu_map);
bpf_map_area_free(cmap);