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bpf_object__find_program_by_title’ is deprecated: libbpf v0.7+: use bpf_object__find_program_by_name() instead See: https://github.com/libbpf/libbpf/issues/297 libbpf#297 Deprecate bpf_program__title() in favor of bpf_program__section_name(). “Title” term is confusing and unconventional, it’s SEC() in code and “section name” everywhere else. Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Demonstration of close() hang on bpf_link fd close
This is a minimal example to demonstrate an issue where close()'ing an fd for a
bpf_link kernel structure will hang indefinitely if the system is fully loaded.
This only happens on a kernel compiled with CONFIG_PREEMPT=y, but on such a
kernel the issue is quite easy to trigger: Simply load up the system (with work
inside the kernel; sending it a lot of network traffic works pretty well), and
run the bpf-link-hang program as root. The program will hang until load is
lowered…
The hang happens in synchronize_rcu_tasks(), which can be seen with this
bpftrace invocation:
bpftrace -e 'kprobe:synchronize_rcu_tasks { @start = nsecs; printf("enter\n"); } kretprobe:synchronize_rcu_tasks { printf("exit after %d ms\n", (nsecs - @start) / 1000000); }'