[PATCH][RESEND] Tracing/fastboot: Enable boot tracing only during initcalls - Kernel

This is a discussion on [PATCH][RESEND] Tracing/fastboot: Enable boot tracing only during initcalls - Kernel ; We used to disable the initcall tracing at a specified time (IE: end of builtin initcalls). But we don't need it anymore. It will be stopped when initcalls are finished. However we want two things: _Start this tracing only after ...

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Thread: [PATCH][RESEND] Tracing/fastboot: Enable boot tracing only during initcalls

  1. [PATCH][RESEND] Tracing/fastboot: Enable boot tracing only during initcalls

    We used to disable the initcall tracing at a specified time (IE: end of builtin initcalls).
    But we don't need it anymore. It will be stopped when initcalls are
    finished.
    However we want two things:

    _Start this tracing only after pre-smp initcalls are finished.
    _Since we are planning to trace sched_switches at the same time, we want to
    enable them only during the initcall execution. For this purpose, this patch
    introduce two functions to enable/disable the sched_switch tracing during boot.

    Signed-off-by: Frederic Weisbecker
    ---
    include/linux/ftrace.h | 24 ++++++++++++++++++++++--
    init/main.c | 4 +++-
    kernel/trace/trace_boot.c | 28 ++++++++++++++++------------
    3 files changed, 41 insertions(+), 15 deletions(-)

    diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
    index 899ec4b..8207aa2 100644
    --- a/include/linux/ftrace.h
    +++ b/include/linux/ftrace.h
    @@ -231,6 +231,11 @@ ftrace_init_module(unsigned long *start, unsigned long *end) { }
    #endif


    +/*
    + * Structure which defines the trace of an initcall.
    + * You don't have to fill the func field since it is
    + * only used internally by the tracer.
    + */
    struct boot_trace {
    pid_t caller;
    char func[KSYM_NAME_LEN];
    @@ -241,13 +246,28 @@ struct boot_trace {
    };

    #ifdef CONFIG_BOOT_TRACER
    +/* Append the trace on the ring-buffer */
    extern void trace_boot(struct boot_trace *it, initcall_t fn);
    +
    +/* Tells the tracer that smp_pre_initcall is finished.
    + * So we can start the tracing
    + */
    extern void start_boot_trace(void);
    -extern void stop_boot_trace(void);
    +
    +/* Resume the tracing of other necessary events
    + * such as sched switches
    + */
    +extern void enable_boot_trace(void);
    +
    +/* Suspend this tracing. Actually, only sched_switches tracing have
    + * to be suspended. Initcalls doesn't need it.)
    + */
    +extern void disable_boot_trace(void);
    #else
    static inline void trace_boot(struct boot_trace *it, initcall_t fn) { }
    static inline void start_boot_trace(void) { }
    -static inline void stop_boot_trace(void) { }
    +static inline void enable_boot_trace(void) { }
    +static inline void disable_boot_trace(void) { }
    #endif


    diff --git a/init/main.c b/init/main.c
    index 73f5e1e..cc8d5be 100644
    --- a/init/main.c
    +++ b/init/main.c
    @@ -721,6 +721,7 @@ int do_one_initcall(initcall_t fn)
    it.caller = task_pid_nr(current);
    printk("calling %pF @ %i\n", fn, it.caller);
    it.calltime = ktime_get();
    + enable_boot_trace();
    }

    it.result = fn();
    @@ -732,6 +733,7 @@ int do_one_initcall(initcall_t fn)
    printk("initcall %pF returned %d after %Ld usecs\n", fn,
    it.result, it.duration);
    trace_boot(&it, fn);
    + disable_boot_trace();
    }

    msgbuf[0] = 0;
    @@ -895,7 +897,7 @@ static int __init kernel_init(void * unused)
    * we're essentially up and running. Get rid of the
    * initmem segments and start the user-mode stuff..
    */
    - stop_boot_trace();
    +
    init_post();
    return 0;
    }
    diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
    index d0a5e50..d104d5b 100644
    --- a/kernel/trace/trace_boot.c
    +++ b/kernel/trace/trace_boot.c
    @@ -13,23 +13,29 @@
    #include "trace.h"

    static struct trace_array *boot_trace;
    -static int trace_boot_enabled;
    +static bool pre_initcalls_finished;

    -
    -/* Should be started after do_pre_smp_initcalls() in init/main.c */
    +/* Tells the boot tracer that the pre_smp_initcalls are finished.
    + * So we are ready .
    + * It doesn't enable sched events tracing however.
    + * You have to call enable_boot_trace to do so.
    + */
    void start_boot_trace(void)
    {
    - trace_boot_enabled = 1;
    + pre_initcalls_finished = true;
    +}
    +
    +void enable_boot_trace(void)
    +{
    }

    -void stop_boot_trace(void)
    +void disable_boot_trace(void)
    {
    - trace_boot_enabled = 0;
    }

    void reset_boot_trace(struct trace_array *tr)
    {
    - stop_boot_trace();
    + disable_boot_trace();
    }

    static void boot_trace_init(struct trace_array *tr)
    @@ -37,8 +43,6 @@ static void boot_trace_init(struct trace_array *tr)
    int cpu;
    boot_trace = tr;

    - trace_boot_enabled = 0;
    -
    for_each_cpu_mask(cpu, cpu_possible_map)
    tracing_reset(tr, cpu);
    }
    @@ -46,9 +50,9 @@ static void boot_trace_init(struct trace_array *tr)
    static void boot_trace_ctrl_update(struct trace_array *tr)
    {
    if (tr->ctrl)
    - start_boot_trace();
    + enable_boot_trace();
    else
    - stop_boot_trace();
    + disable_boot_trace();
    }

    static enum print_line_t initcall_print_line(struct trace_iterator *iter)
    @@ -99,7 +103,7 @@ void trace_boot(struct boot_trace *it, initcall_t fn)
    unsigned long irq_flags;
    struct trace_array *tr = boot_trace;

    - if (!trace_boot_enabled)
    + if (!pre_initcalls_finished)
    return;

    /* Get its name now since this function could
    --
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  2. Re: [PATCH][RESEND] Tracing/fastboot: Enable boot tracing only during initcalls


    applied these 6 patches from you to tip/tracing/fastboot:

    79a9d46: tracing/ftrace: fix a bug when switch current tracer to sched tracer
    efade6e: tracing/ftrace: types and naming corrections for sched tracer
    d7ad44b: tracing/fastboot: use sched switch tracer from boot tracer
    e55f605c: tracing/ftrace: remove unused code in sched_switch tracer
    07695fa: tracing/ftrace: fix a race condition in sched_switch tracer
    71566a0: tracing/fastboot: Enable boot tracing only during initcalls

    thanks Frederic!

    Ingo
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