Re: ftrace doesn't work - 1211 upstream kernel

["Terje Bergström" <tbergstrom-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>]

On 12.12.2012 13:27, Mark Zhang wrote:
> Hi all,
> 
> Has anyone tried to use ftrace to debug upstream kernel? I tried today
> but the result is, the serial console hung after ftrace enabled(kernel
> is alive because the Magic SysRq works).
> 
> My steps are:
> - Enable CONFIG_FUNCTION_TRACER in kernel config
> - Enter command: echo 0 > /sys/kernel/debug/tracing/tracing_on;echo
> function > /sys/kernel/debug/tracing/current_tracer;echo 1 >
> /proc/sys/kernel/ftrace_dump_on_oops
> - Then sometimes the serial console hangs right after you entered the
> command above, or hangs when you try to "cat /sys/kernel/debug/trace"
> 
> I dumped some backtraces(check below, by invoking a system crash
> manually) and hope it helps:

I'm using ftrace to debug host1x driver + tegradrm, running on Tegra2
ventana. I just rebased them on linux-next, and I use just the events,
not function tracing.

echo 1 >/sys/kernel/debug/tracing/events/host1x/enable
~/drm/tests/tegra/2d/tegra_2d_tests
cat /sys/kernel/debug/tracing/trace

I get host1x events as expected.

Also function tracing works.

Terje