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linuxftrace

How to make a linux kernel function available to ftrace?

I want to trace 2 functions in some kernel module that are called during suspend/resume.

These functions do appear in "available_filter_functions".

This is how I am configuring ftrace:

echo nop > current_tracer
echo fun_suspend > set_ftrace_filter
echo fun_resume > set_ftrace_filter
echo function_graph > current_tracer

When I suspend/resume the machine, these functions are called for sure (I see logs) yet do not appear in cat trace

Does anyone have any idea?

Thanks,

Matti

Solution

  • The functions that i wanted to measure were in a suspend resume flow. And apparently suspend & resume are very problematic for tracing functions(dynamic tracing), and ftrace disables the tracing during this process. So for now you cannot trace those functions.