• Steven Rostedt's avatar
    ftrace: add ftrace_graph_stop() · 14a866c5
    Steven Rostedt authored
    
    
    Impact: new ftrace_graph_stop function
    
    While developing more features of function graph, I hit a bug that
    caused the WARN_ON to trigger in the prepare_ftrace_return function.
    Well, it was hard for me to find out that was happening because the
    bug would not print, it would just cause a hard lockup or reboot.
    The reason is that it is not safe to call printk from this function.
    
    Looking further, I also found that it calls unregister_ftrace_graph,
    which grabs a mutex and calls kstop machine. This would definitely
    lock the box up if it were to trigger.
    
    This patch adds a fast and safe ftrace_graph_stop() which will
    stop the function tracer. Then it is safe to call the WARN ON.
    Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    14a866c5
ftrace.h 11.7 KB