Comment 4 for bug 1940972

... I've looked at this test and the following occurs:

0. go to the tracking directory:

cd /sys/kernel/debug/tracing

1. tracer is disabled:

echo 0 > /proc/sys/kernel/stack_tracer_enabled

2. tracer is set to track all kernel functions with *lock* in the name:

echo '*lock*' > stack_trace_filter

(this takes a few minutes to configure, it's quite slow).

one can see the functions filtered on by using cat stack_trace_filter

3. emabling the tracer:

echo 0 > stack_max_size
echo 1 > /proc/sys/kernel/stack_tracer_enabled

4. check if the tracer has found any functions that match:

cat stack_trace | grep lock

..none appear in position 0 in the stack_trace file. This works on other arches such as arm64, amd64, s390x etc..