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    SubjectRe: Ftrace: can trace kthread?
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    On Thu, Oct 21, 2010 at 4:44 PM, Figo.zhang
    <zhangtianfei@leadcoretech.com> wrote:
    >
    >> > i try by set_ftrace_pid, it also can't ftrace the kswapd.
    >>
    >> Are you sure kswapd got chance to run on your system?
    >>
    >> BTW, I can successfully trace bdi_writeback_thread,
    >> # tracer: function
    >> #
    >> #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
    >> #              | |       |          |         |
    >>        flush-8:0-374   [000] 600743.828496: finish_task_switch <-schedule
    >>        flush-8:0-374   [000] 600743.828498: perf_event_task_sched_in
    >> <-finish_task_switch
    >>        flush-8:0-374   [000] 600743.828498: del_timer_sync <-schedule_timeout
    >>        flush-8:0-374   [000] 600743.828499: try_to_del_timer_sync
    >> <-del_timer_sync
    >>        flush-8:0-374   [000] 600743.828499: lock_timer_base
    >> <-try_to_del_timer_sync
    >>        flush-8:0-374   [000] 600743.828499: _spin_lock_irqsave <-lock_timer_base
    >>        flush-8:0-374   [000] 600743.828500: _spin_unlock_irqrestore
    >> <-try_to_del_timer_sync
    >>        flush-8:0-374   [000] 600743.828500: kthread_should_stop
    >> <-bdi_writeback_task
    >
    > are you use my scprit to trace the bdi_writeback_thread ?

    No.

    I just
    echo 0 > tracing_enabled
    echo function > current_tracer
    echo 374(pid of flush) > set_ftrace_pid
    echo 1 > tracing_enabled
    wait some time
    echo 0 > tracing_enabled
    cat trace

    So I think this answer your question "could kthread be traced?"

    Thanks,
    Yong
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