If some of the subtests use module BTFs through ksyms, they will cause
bpf_prog to take a refcount on bpf_testmod module, which will prevent it from
successfully unloading. Module's refcnt is decremented when bpf_prog is freed,
which generally happens in RCU callback. So we need to trigger
syncronize_rcu() in the kernel, which can be achieved nicely with
membarrier(MEMBARRIER_CMD_GLOBAL) syscall. So do that in kernel_sync_rcu() and
make it available to other test inside the test_progs. This synchronize_rcu()
is called before attempting to unload bpf_testmod.
Fixes: 9f7fa225894c ("selftests/bpf: Add bpf_testmod kernel module for testing")
Suggested-by: Alexei Starovoitov <ast@xxxxxxxxxx>
Signed-off-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
---
.../selftests/bpf/prog_tests/btf_map_in_map.c | 33 -------------------
tools/testing/selftests/bpf/test_progs.c | 11 +++++++
tools/testing/selftests/bpf/test_progs.h | 1 +
3 files changed, 12 insertions(+), 33 deletions(-)
diff --git a/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c b/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c
index 76ebe4c250f1..eb90a6b8850d 100644
--- a/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c
+++ b/tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c
@@ -20,39 +20,6 @@ static __u32 bpf_map_id(struct bpf_map *map)
return info.id;
}
-/*
- * Trigger synchronize_rcu() in kernel.
- *
- * ARRAY_OF_MAPS/HASH_OF_MAPS lookup/update operations trigger synchronize_rcu()
- * if looking up an existing non-NULL element or updating the map with a valid
- * inner map FD. Use this fact to trigger synchronize_rcu(): create map-in-map,
- * create a trivial ARRAY map, update map-in-map with ARRAY inner map. Then
- * cleanup. At the end, at least one synchronize_rcu() would be called.
- */
-static int kern_sync_rcu(void)
-{
- int inner_map_fd, outer_map_fd, err, zero = 0;
-
- inner_map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, 4, 4, 1, 0);
- if (CHECK(inner_map_fd < 0, "inner_map_create", "failed %d\n", -errno))
- return -1;
-
- outer_map_fd = bpf_create_map_in_map(BPF_MAP_TYPE_ARRAY_OF_MAPS, NULL,
- sizeof(int), inner_map_fd, 1, 0);
- if (CHECK(outer_map_fd < 0, "outer_map_create", "failed %d\n", -errno)) {
- close(inner_map_fd);
- return -1;
- }
-
- err = bpf_map_update_elem(outer_map_fd, &zero, &inner_map_fd, 0);
- if (err)
- err = -errno;
- CHECK(err, "outer_map_update", "failed %d\n", err);
- close(inner_map_fd);
- close(outer_map_fd);
- return err;
-}
-
static void test_lookup_update(void)
{
int map1_fd, map2_fd, map3_fd, map4_fd, map5_fd, map1_id, map2_id;
diff --git a/tools/testing/selftests/bpf/test_progs.c b/tools/testing/selftests/bpf/test_progs.c
index 7d077d48cadd..e3fbca25696c 100644
--- a/tools/testing/selftests/bpf/test_progs.c
+++ b/tools/testing/selftests/bpf/test_progs.c
@@ -11,6 +11,7 @@
#include <signal.h>
#include <string.h>
#include <execinfo.h> /* backtrace */
+#include <linux/membarrier.h>
#define EXIT_NO_TEST 2
#define EXIT_ERR_SETUP_INFRA 3
@@ -370,8 +371,18 @@ static int delete_module(const char *name, int flags)
return syscall(__NR_delete_module, name, flags);
}
+/*
+ * Trigger synchronize_rcu() in kernel.
+ */
+int kern_sync_rcu(void)
+{
+ return syscall(__NR_membarrier, MEMBARRIER_CMD_GLOBAL, 0, 0);
+}
+
static void unload_bpf_testmod(void)
{
+ if (kern_sync_rcu())
+ fprintf(env.stderr, "Failed to trigger kernel-side RCU sync!\n");
if (delete_module("bpf_testmod", 0)) {
if (errno == ENOENT) {
if (env.verbosity > VERBOSE_NONE)
diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h
index 115953243f62..e49e2fdde942 100644
--- a/tools/testing/selftests/bpf/test_progs.h
+++ b/tools/testing/selftests/bpf/test_progs.h
@@ -219,6 +219,7 @@ int bpf_find_map(const char *test, struct bpf_object *obj, const char *name);
int compare_map_keys(int map1_fd, int map2_fd);
int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len);
int extract_build_id(char *build_id, size_t size);
+int kern_sync_rcu(void);
#ifdef __x86_64__
#define SYS_NANOSLEEP_KPROBE_NAME "__x64_sys_nanosleep"
--
2.24.1
