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H A D | sockopt_inherit.c | e81e7a53 Wed Jul 15 17:41:07 CDT 2020 Stanislav Fomichev <sdf@google.com> selftests/bpf: Fix possible hang in sockopt_inherit
Andrii reported that sockopt_inherit occasionally hangs up on 5.5 kernel [0]. This can happen if server_thread runs faster than the main thread. In that case, pthread_cond_wait will wait forever because pthread_cond_signal was executed before the main thread was blocking. Let's move pthread_mutex_lock up a bit to make sure server_thread runs strictly after the main thread goes to sleep.
(Not sure why this is 5.5 specific, maybe scheduling is less deterministic? But I was able to confirm that it does indeed happen in a VM.)
[0] https://lore.kernel.org/bpf/CAEf4BzY0-bVNHmCkMFPgObs=isUAyg-dFzGDY7QWYkmm7rmTSg@mail.gmail.com/
Reported-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20200715224107.3591967-1-sdf@google.com e81e7a53 Wed Jul 15 17:41:07 CDT 2020 Stanislav Fomichev <sdf@google.com> selftests/bpf: Fix possible hang in sockopt_inherit Andrii reported that sockopt_inherit occasionally hangs up on 5.5 kernel [0]. This can happen if server_thread runs faster than the main thread. In that case, pthread_cond_wait will wait forever because pthread_cond_signal was executed before the main thread was blocking. Let's move pthread_mutex_lock up a bit to make sure server_thread runs strictly after the main thread goes to sleep. (Not sure why this is 5.5 specific, maybe scheduling is less deterministic? But I was able to confirm that it does indeed happen in a VM.) [0] https://lore.kernel.org/bpf/CAEf4BzY0-bVNHmCkMFPgObs=isUAyg-dFzGDY7QWYkmm7rmTSg@mail.gmail.com/ Reported-by: Andrii Nakryiko <andriin@fb.com> Signed-off-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrii Nakryiko <andriin@fb.com> Link: https://lore.kernel.org/bpf/20200715224107.3591967-1-sdf@google.com
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