From: Rajesh Bhagat Date: Fri, 17 Feb 2012 08:29:15 +0000 (+0530) Subject: ftrace: Fix function_graph for archs that test ftrace_trace_function X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=db6544e0075d192e5ad16eda8689c55fa9c6f8f4;p=mv-sheeva.git ftrace: Fix function_graph for archs that test ftrace_trace_function When CONFIG_DYNAMIC_FTRACE is not set, some archs (ARM) test the variable function_trace_function to determine if it should call the function tracer. If it is not set to ftrace_stub, then it will call the function and return, and not call the function graph tracer. But some of these archs (ARM) do not have the assembly code to test if function tracing is enabled or not (quick stop of tracing) and it calls the helper routine ftrace_test_stop_func() instead. If function tracer is enabled and then disabled, the variable ftrace_trace_function is still set to the helper routine ftrace_test_stop_func(), and not to ftrace_stub. This will prevent the function graph tracer from ever running. Output before patch /debug/tracing # echo function > current_tracer /debug/tracing # echo function_graph > current_tracer /debug/tracing # cat trace Output after patch /debug/tracing # echo function > current_tracer /debug/tracing # echo function_graph > current_tracer /debug/tracing # cat trace 0) ! 253.375 us | } /* irq_enter */ 0) | generic_handle_irq() { 0) | handle_fasteoi_irq() { 0) 9.208 us | _raw_spin_lock(); 0) | handle_irq_event() { 0) | handle_irq_event_percpu() { Signed-off-by: Rajesh Bhagat Signed-off-by: Steven Rostedt --- diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 867bd1dd2dd..0fa92f677c9 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -249,7 +249,8 @@ static void update_ftrace_function(void) #else __ftrace_trace_function = func; #endif - ftrace_trace_function = ftrace_test_stop_func; + ftrace_trace_function = + (func == ftrace_stub) ? func : ftrace_test_stop_func; #endif }