Commit c2e42ddf authored by Hou Tao's avatar Hou Tao Committed by Alexei Starovoitov
Browse files

bpf, cpumask: Clean up bpf_cpu_map_entry directly in cpu_map_free 



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: default avatarHou Tao <houtao1@huawei.com>
Reviewed-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20230816045959.358059-3-houtao@huaweicloud.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 8f8500a2

kernel/bpf/cpumap.c

+8 −9
Original line number Diff line number Diff line
@@ -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);