On Tue, 10 Dec 2024 16:11:16 +0100 Linus Walleij <[email protected]> wrote:
> This patch regressed boot-time tracing for me. > > How to reproduce: > - Enable CONFIG_FTRACE, CONFIG_FUNCTION_TRACER, > CONFIG_BOOTTIME_TRACING > - Pass command line > ftrace=function_graph ftrace_graph_filter=do_idle > to make ftrace trace this function all through the boot process. > > Before this patch: > > cd /sys/kernel/debug/tracing > cat trace > > gives a nice trace of all invocations of do_idle() during boot. > > After this patch: > > cd /sys/kernel/debug/tracing > cat trace > > Gives an empty trace :( > > And: > > cat current_tracer > function_graph > cat set_graph_function > do_idle > cat tracing_on > 1 > > So all *is* set up, just not performing > > I tried to figure out why this happens but I'm not good with tracing > internals. Any ideas? Thanks for the report. I'm currently at the ELISA workshop this week, but will try to reproduce it. -- Steve
