Hi, Could someone explain me why return probes of some syscalls (for example: futex, poll, epoll_wait) sometimes are not called? It can be reproduced using the following bash script: https://gist.github.com/ldorau/c439d9ec7635409a5016c42e3a9121ec Here are results gathered from 60 seconds test run on kernel 4.9.12 (Fedora 24): futex: p 56904 r 5489 (90% did not return (51415)) poll: p 43466 r 7703 (82% did not return (35763)) epoll_wait: p 73366 r 23551 (67% did not return (49815)) The whole log is attached below. Lukasz --- # ./test_kprobes.sh 60 Will trace using following kprobe_events: r:kprobes/r_futex sys_futex p:kprobes/p_futex sys_futex r:kprobes/r_poll sys_poll p:kprobes/p_poll sys_poll r:kprobes/r_epoll_wait sys_epoll_wait p:kprobes/p_epoll_wait sys_epoll_wait r:kprobes/r_select sys_select p:kprobes/p_select sys_select r:kprobes/r_fork sys_fork p:kprobes/p_fork sys_fork r:kprobes/r_vfork sys_vfork p:kprobes/p_vfork sys_vfork r:kprobes/r_mmap sys_mmap p:kprobes/p_mmap sys_mmap r:kprobes/r_open sys_open p:kprobes/p_open sys_open r:kprobes/r_close sys_close p:kprobes/p_close sys_close r:kprobes/r_write sys_write p:kprobes/p_write sys_write r:kprobes/r_read sys_read p:kprobes/p_read sys_read Results (60 sec): futex: p 56904 r 5489 (90% did not return (51415)) poll: p 43466 r 7703 (82% did not return (35763)) epoll_wait: p 73366 r 23551 (67% did not return (49815)) select: p 13355 r 13351 (0% did not return (4)) fork: p 0 r 0 (OK) vfork: p 0 r 0 (OK) mmap: p 4328 r 4328 (OK) open: p 4579 r 4579 (OK) close: p 7163 r 7163 (OK) write: p 22769 r 22769 (OK) read: p 40014 r 40014 (OK) -- To unsubscribe from this list: send the line "unsubscribe linux-trace-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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