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    Subject[PATCH 3.4 11/43] ftrace: Initialize the ftrace profiler for each possible cpu
    Date
    3.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Miao Xie <miaox@cn.fujitsu.com>

    commit c4602c1c818bd6626178d6d3fcc152d9f2f48ac0 upstream.

    Ftrace currently initializes only the online CPUs. This implementation has
    two problems:
    - If we online a CPU after we enable the function profile, and then run the
    test, we will lose the trace information on that CPU.
    Steps to reproduce:
    # echo 0 > /sys/devices/system/cpu/cpu1/online
    # cd <debugfs>/tracing/
    # echo <some function name> >> set_ftrace_filter
    # echo 1 > function_profile_enabled
    # echo 1 > /sys/devices/system/cpu/cpu1/online
    # run test
    - If we offline a CPU before we enable the function profile, we will not clear
    the trace information when we enable the function profile. It will trouble
    the users.
    Steps to reproduce:
    # cd <debugfs>/tracing/
    # echo <some function name> >> set_ftrace_filter
    # echo 1 > function_profile_enabled
    # run test
    # cat trace_stat/function*
    # echo 0 > /sys/devices/system/cpu/cpu1/online
    # echo 0 > function_profile_enabled
    # echo 1 > function_profile_enabled
    # cat trace_stat/function*
    # run test
    # cat trace_stat/function*

    So it is better that we initialize the ftrace profiler for each possible cpu
    every time we enable the function profile instead of just the online ones.

    Link: http://lkml.kernel.org/r/1387178401-10619-1-git-send-email-miaox@cn.fujitsu.com

    Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/trace/ftrace.c | 2 +-
    1 file changed, 1 insertion(+), 1 deletion(-)

    --- a/kernel/trace/ftrace.c
    +++ b/kernel/trace/ftrace.c
    @@ -688,7 +688,7 @@ static int ftrace_profile_init(void)
    int cpu;
    int ret = 0;

    - for_each_online_cpu(cpu) {
    + for_each_possible_cpu(cpu) {
    ret = ftrace_profile_init_cpu(cpu);
    if (ret)
    break;



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