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authorAlexei Starovoitov <ast@kernel.org>2020-06-29 21:33:39 -0700
committerAlexei Starovoitov <ast@kernel.org>2020-07-01 08:07:13 -0700
commitbba1dc0b55ac462d24ed1228ad49800c238cd6d7 (patch)
treed83554930260fe70393ea2d74734357577035dce /kernel/bpf/hashtab.c
parentselftests/bpf: Add byte swapping selftest (diff)
downloadlinux-dev-bba1dc0b55ac462d24ed1228ad49800c238cd6d7.tar.xz
linux-dev-bba1dc0b55ac462d24ed1228ad49800c238cd6d7.zip
bpf: Remove redundant synchronize_rcu.
bpf_free_used_maps() or close(map_fd) will trigger map_free callback. bpf_free_used_maps() is called after bpf prog is no longer executing: bpf_prog_put->call_rcu->bpf_prog_free->bpf_free_used_maps. Hence there is no need to call synchronize_rcu() to protect map elements. Note that hash_of_maps and array_of_maps update/delete inner maps via sys_bpf() that calls maybe_wait_bpf_programs() and synchronize_rcu(). Signed-off-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Andrii Nakryiko <andriin@fb.com> Acked-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/bpf/20200630043343.53195-2-alexei.starovoitov@gmail.com
Diffstat (limited to 'kernel/bpf/hashtab.c')
-rw-r--r--kernel/bpf/hashtab.c8
1 files changed, 3 insertions, 5 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index acd06081d81d..d4378d7d442b 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1290,12 +1290,10 @@ static void htab_map_free(struct bpf_map *map)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
- /* at this point bpf_prog->aux->refcnt == 0 and this map->refcnt == 0,
- * so the programs (can be more than one that used this map) were
- * disconnected from events. Wait for outstanding critical sections in
- * these programs to complete
+ /* bpf_free_used_maps() or close(map_fd) will trigger this map_free callback.
+ * bpf_free_used_maps() is called after bpf prog is no longer executing.
+ * There is no need to synchronize_rcu() here to protect map elements.
*/
- synchronize_rcu();
/* some of free_htab_elem() callbacks for elements of this map may
* not have executed. Wait for them.