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    Subject[PATCH 06/12 v3] ftrace: only have ftrace_kill atomic
    When an anomaly is detected, we need a way to completely disable
    ftrace. Right now we have two functions: ftrace_kill and ftrace_kill_atomic.
    The ftrace_kill tries to do it in a "nice" way by converting everything
    back to a nop.

    The "nice" way is dangerous itself, so this patch removes it and only
    has the "atomic" version, which is all that is needed.

    Signed-off-by: Steven Rostedt <srostedt@redhat.com>
    ---
    include/linux/ftrace.h | 3 +--
    kernel/trace/ftrace.c | 42 ++----------------------------------------
    kernel/trace/trace.c | 2 +-
    3 files changed, 4 insertions(+), 43 deletions(-)

    Index: linux-compile.git/include/linux/ftrace.h
    ===================================================================
    --- linux-compile.git.orig/include/linux/ftrace.h 2008-10-22 15:57:31.000000000 -0400
    +++ linux-compile.git/include/linux/ftrace.h 2008-10-22 15:58:35.000000000 -0400
    @@ -40,7 +40,7 @@ extern void ftrace_stub(unsigned long a0
    # define register_ftrace_function(ops) do { } while (0)
    # define unregister_ftrace_function(ops) do { } while (0)
    # define clear_ftrace_function(ops) do { } while (0)
    -static inline void ftrace_kill_atomic(void) { }
    +static inline void ftrace_kill(void) { }
    #endif /* CONFIG_FTRACE */

    #ifdef CONFIG_DYNAMIC_FTRACE
    @@ -117,7 +117,6 @@ static inline void ftrace_release(void *

    /* totally disable ftrace - can not re-enable after this */
    void ftrace_kill(void);
    -void ftrace_kill_atomic(void);

    static inline void tracer_disable(void)
    {
    Index: linux-compile.git/kernel/trace/ftrace.c
    ===================================================================
    --- linux-compile.git.orig/kernel/trace/ftrace.c 2008-10-22 15:49:49.000000000 -0400
    +++ linux-compile.git/kernel/trace/ftrace.c 2008-10-22 15:58:35.000000000 -0400
    @@ -1544,22 +1544,6 @@ int ftrace_force_update(void)
    return ret;
    }

    -static void ftrace_force_shutdown(void)
    -{
    - struct task_struct *task;
    - int command = FTRACE_DISABLE_CALLS | FTRACE_UPDATE_TRACE_FUNC;
    -
    - mutex_lock(&ftraced_lock);
    - task = ftraced_task;
    - ftraced_task = NULL;
    - ftraced_suspend = -1;
    - ftrace_run_update_code(command);
    - mutex_unlock(&ftraced_lock);
    -
    - if (task)
    - kthread_stop(task);
    -}
    -
    static __init int ftrace_init_debugfs(void)
    {
    struct dentry *d_tracer;
    @@ -1752,17 +1736,16 @@ core_initcall(ftrace_dynamic_init);
    # define ftrace_shutdown() do { } while (0)
    # define ftrace_startup_sysctl() do { } while (0)
    # define ftrace_shutdown_sysctl() do { } while (0)
    -# define ftrace_force_shutdown() do { } while (0)
    #endif /* CONFIG_DYNAMIC_FTRACE */

    /**
    - * ftrace_kill_atomic - kill ftrace from critical sections
    + * ftrace_kill - kill ftrace
    *
    * This function should be used by panic code. It stops ftrace
    * but in a not so nice way. If you need to simply kill ftrace
    * from a non-atomic section, use ftrace_kill.
    */
    -void ftrace_kill_atomic(void)
    +void ftrace_kill(void)
    {
    ftrace_disabled = 1;
    ftrace_enabled = 0;
    @@ -1773,27 +1756,6 @@ void ftrace_kill_atomic(void)
    }

    /**
    - * ftrace_kill - totally shutdown ftrace
    - *
    - * This is a safety measure. If something was detected that seems
    - * wrong, calling this function will keep ftrace from doing
    - * any more modifications, and updates.
    - * used when something went wrong.
    - */
    -void ftrace_kill(void)
    -{
    - mutex_lock(&ftrace_sysctl_lock);
    - ftrace_disabled = 1;
    - ftrace_enabled = 0;
    -
    - clear_ftrace_function();
    - mutex_unlock(&ftrace_sysctl_lock);
    -
    - /* Try to totally disable ftrace */
    - ftrace_force_shutdown();
    -}
    -
    -/**
    * register_ftrace_function - register a function for profiling
    * @ops - ops structure that holds the function for profiling.
    *
    Index: linux-compile.git/kernel/trace/trace.c
    ===================================================================
    --- linux-compile.git.orig/kernel/trace/trace.c 2008-10-22 15:09:04.000000000 -0400
    +++ linux-compile.git/kernel/trace/trace.c 2008-10-22 15:58:35.000000000 -0400
    @@ -3097,7 +3097,7 @@ void ftrace_dump(void)
    dump_ran = 1;

    /* No turning back! */
    - ftrace_kill_atomic();
    + ftrace_kill();

    for_each_tracing_cpu(cpu) {
    atomic_inc(&global_trace.data[cpu]->disabled);
    --


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