selftests/bpf: Fix flakiness of task_local_storage/sys_enter_exit

The test_sys_enter_exit test was setting target_pid before attaching
the BPF programs, which causes syscalls made during the attach phase
to be counted. This is flaky because, apparently, there is no
guarantee that both on_enter and on_exit will trigger during the
attachment.

Move the target_pid assignment to after task_local_storage__attach()
so that only explicit sys_gettid() calls are counted.

Reported-by: BPF CI Bot (Claude Opus 4.6) <bot+bpf-ci@kernel.org>
Closes: https://github.com/kernel-patches/vmtest/issues/448
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260224211202.214325-1-ihor.solodrai@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
index 7bee33797c710450159b4c24023a61c545490c5f..1b26c12f255a74930fd52caa837842ed074e42fe 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
+++ b/tools/testing/selftests/bpf/prog_tests/task_local_storage.c
@@ -25,24 +25,30 @@
 static void test_sys_enter_exit(void)
 {
        struct task_local_storage *skel;
+       pid_t pid = sys_gettid();
        int err;
 
        skel = task_local_storage__open_and_load();
        if (!ASSERT_OK_PTR(skel, "skel_open_and_load"))
                return;
 
-       skel->bss->target_pid = sys_gettid();
-
        err = task_local_storage__attach(skel);
        if (!ASSERT_OK(err, "skel_attach"))
                goto out;
 
+       /* Set target_pid after attach so that syscalls made during
+        * attach are not counted.
+        */
+       skel->bss->target_pid = pid;
+
        sys_gettid();
        sys_gettid();
 
-       /* 3x syscalls: 1x attach and 2x gettid */
-       ASSERT_EQ(skel->bss->enter_cnt, 3, "enter_cnt");
-       ASSERT_EQ(skel->bss->exit_cnt, 3, "exit_cnt");
+       skel->bss->target_pid = 0;
+
+       /* 2x gettid syscalls */
+       ASSERT_EQ(skel->bss->enter_cnt, 2, "enter_cnt");
+       ASSERT_EQ(skel->bss->exit_cnt, 2, "exit_cnt");
        ASSERT_EQ(skel->bss->mismatch_cnt, 0, "mismatch_cnt");
 out:
        task_local_storage__destroy(skel);