When loading in parallel multiple programs which use the same to-be
pinned map, it is possible that two instances of the loader will call
bpf_object__create_maps() at the same time. If the map doesn't exist
when both instances call bpf_object__reuse_map(), then one of the
instances will fail with EEXIST when calling bpf_map__pin().
Fix the race by retrying creating a map if bpf_map__pin() returns
EEXIST. The fix is similar to the one in iproute2: e4c4685fd6e4 ("bpf:
Fix race condition with map pinning").
Cc: Joe Stringer <joe@xxxxxxxxxxx>
Signed-off-by: Martynas Pumputis <m@xxxxxxxxx>
---
tools/lib/bpf/libbpf.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 1e04ce724240..7a31c7c3cd21 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4616,10 +4616,12 @@ bpf_object__create_maps(struct bpf_object *obj)
char *cp, errmsg[STRERR_BUFSIZE];
unsigned int i, j;
int err;
+ bool retried = false;
for (i = 0; i < obj->nr_maps; i++) {
map = &obj->maps[i];
+retry:
if (map->pin_path) {
err = bpf_object__reuse_map(map);
if (err) {
@@ -4660,9 +4662,13 @@ bpf_object__create_maps(struct bpf_object *obj)
if (map->pin_path && !map->pinned) {
err = bpf_map__pin(map, NULL);
if (err) {
+ zclose(map->fd);
+ if (!retried && err == EEXIST) {
+ retried = true;
+ goto retry;
+ }
pr_warn("map '%s': failed to auto-pin at '%s': %d\n",
map->name, map->pin_path, err);
- zclose(map->fd);
goto err_out;
}
}
--
2.32.0
