selftests/bpf: fix test_spin_lock_fail.c's global vars usage

JIRA: https://issues.redhat.com/browse/RHEL-85485

commit 1b2bfc2
Author: Andrii Nakryiko <andrii@kernel.org>
Date:   Tue Oct 22 21:39:06 2024 -0700

    selftests/bpf: fix test_spin_lock_fail.c's global vars usage

    Global variables of special types (like `struct bpf_spin_lock`) make
    underlying ARRAY maps non-mmapable. To make this work with libbpf's
    mmaping logic, application is expected to declare such special variables
    as static, so libbpf doesn't even attempt to mmap() such ARRAYs.

    test_spin_lock_fail.c didn't follow this rule, but given it relied on
    this test to trigger failures, this went unnoticed, as we never got to
    the step of mmap()'ing these ARRAY maps.

    It is fragile and relies on specific sequence of libbpf steps, which are
    an internal implementation details.

    Fix the test by marking lockA and lockB as static.

    Fixes: c48748a ("selftests/bpf: Add failure test cases for spin lock pairing")
    Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
    Link: https://lore.kernel.org/r/20241023043908.3834423-2-andrii@kernel.org
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Viktor Malik <vmalik@redhat.com>

Author: viktormalik

tools/testing/selftests/bpf/progs/test_spin_lock_fail.c

@@ -28,8 +28,8 @@ struct {
 	},
 };
 
-SEC(".data.A") struct bpf_spin_lock lockA;
-SEC(".data.B") struct bpf_spin_lock lockB;
+static struct bpf_spin_lock lockA SEC(".data.A");
+static struct bpf_spin_lock lockB SEC(".data.B");
 
 SEC("?tc")
 int lock_id_kptr_preserve(void *ctx)