Eric Lee / smarc-fsl-linux-kernel

14 May, 2010

1 commit

  • 38516ab59   tracing: Let tracepoints have data passed to tracepoint callbacks ... Browse Code »

    This patch adds data to be passed to tracepoint callbacks.

    The created functions from DECLARE_TRACE() now need a mandatory data
    parameter. For example:

    DECLARE_TRACE(mytracepoint, int value, value)

    Will create the register function:

    int register_trace_mytracepoint((void(*)(void *data, int value))probe,
    void *data);

    As the first argument, all callbacks (probes) must take a (void *data)
    parameter. So a callback for the above tracepoint will look like:

    void myprobe(void *data, int value)
    {
    }

    The callback may choose to ignore the data parameter.

    This change allows callbacks to register a private data pointer along
    with the function probe.

    void mycallback(void *data, int value);

    register_trace_mytracepoint(mycallback, mydata);

    Then the mycallback() will receive the "mydata" as the first parameter
    before the args.

    A more detailed example:

    DECLARE_TRACE(mytracepoint, TP_PROTO(int status), TP_ARGS(status));

    /* In the C file */

    DEFINE_TRACE(mytracepoint, TP_PROTO(int status), TP_ARGS(status));

    [...]

    trace_mytracepoint(status);

    /* In a file registering this tracepoint */

    int my_callback(void *data, int status)
    {
    struct my_struct my_data = data;
    [...]
    }

    [...]
    my_data = kmalloc(sizeof(*my_data), GFP_KERNEL);
    init_my_data(my_data);
    register_trace_mytracepoint(my_callback, my_data);

    The same callback can also be registered to the same tracepoint as long
    as the data registered is different. Note, the data must also be used
    to unregister the callback:

    unregister_trace_mytracepoint(my_callback, my_data);

    Because of the data parameter, tracepoints declared this way can not have
    no args. That is:

    DECLARE_TRACE(mytracepoint, TP_PROTO(void), TP_ARGS());

    will cause an error.

    If no arguments are needed, a new macro can be used instead:

    DECLARE_TRACE_NOARGS(mytracepoint);

    Since there are no arguments, the proto and args fields are left out.

    This is part of a series to make the tracepoint footprint smaller:

    text data bss dec hex filename
    4913961 1088356 861512 6863829 68bbd5 vmlinux.orig
    4914025 1088868 861512 6864405 68be15 vmlinux.class
    4918492 1084612 861512 6864616 68bee8 vmlinux.tracepoint

    Again, this patch also increases the size of the kernel, but
    lays the ground work for decreasing it.

    v5: Fixed net/core/drop_monitor.c to handle these updates.

    v4: Moved the DECLARE_TRACE() DECLARE_TRACE_NOARGS out of the
    #ifdef CONFIG_TRACE_POINTS, since the two are the same in both
    cases. The __DECLARE_TRACE() is what changes.
    Thanks to Frederic Weisbecker for pointing this out.

    v3: Made all register_* functions require data to be passed and
    all callbacks to take a void * parameter as its first argument.
    This makes the calling functions comply with C standards.

    Also added more comments to the modifications of DECLARE_TRACE().

    v2: Made the DECLARE_TRACE() have the ability to pass arguments
    and added a new DECLARE_TRACE_NOARGS() for tracepoints that
    do not need any arguments.

    Acked-by: Mathieu Desnoyers
    Acked-by: Masami Hiramatsu
    Acked-by: Frederic Weisbecker
    Cc: Neil Horman
    Cc: David S. Miller
    Signed-off-by: Steven Rostedt

    Steven Rostedt
     

07 Jan, 2009

1 commit

16 Nov, 2008

1 commit

  • 2504ea5ed   tracepoints: samples, fix teardown ... Browse Code »

    Impact: fix a bug in sample tracepoints

    Need a tracepoint_synchronize_unregister() before the end of exit() to
    make sure every probe callers have exited the non preemptible section
    and thus are not executing the probe code anymore.

    Signed-off-by: Mathieu Desnoyers
    Signed-off-by: Ingo Molnar

    Mathieu Desnoyers
     

14 Oct, 2008

1 commit