• S
    ftrace: add stack trace to function tracer · 53614991
    Steven Rostedt 提交于
    Impact: new feature to stack trace any function
    
    Chris Mason asked about being able to pick and choose a function
    and get a stack trace from it. This feature enables his request.
    
     # echo io_schedule > /debug/tracing/set_ftrace_filter
     # echo function > /debug/tracing/current_tracer
     # echo func_stack_trace > /debug/tracing/trace_options
    
    Produces the following in /debug/tracing/trace:
    
           kjournald-702   [001]   135.673060: io_schedule <-sync_buffer
           kjournald-702   [002]   135.673671:
     <= sync_buffer
     <= __wait_on_bit
     <= out_of_line_wait_on_bit
     <= __wait_on_buffer
     <= sync_dirty_buffer
     <= journal_commit_transaction
     <= kjournald
    
    Note, be careful about turning this on without filtering the functions.
    You may find that you have a 10 second lag between typing and seeing
    what you typed. This is why the stack trace for the function tracer
    does not use the same stack_trace flag as the other tracers use.
    Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
    Signed-off-by: NIngo Molnar <mingo@elte.hu>
    53614991
trace_functions.c 3.1 KB