On Sat, 25 Aug 2018 10:45:09 +0900 Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > On Fri, 24 Aug 2018 19:23:52 -0400 > Steven Rostedt <rostedt@xxxxxxxxxxx> wrote: > > > On Fri, 17 Aug 2018 01:40:30 +0900 > > Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > > > > > Add a testcase for max stack tracer, which checks basic > > > max stack usage tracing and its filter feature. > > > > > > Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > > > --- > > > .../ftrace/test.d/ftrace/func_stack_tracer.tc | 39 ++++++++++++++++++++ > > > 1 file changed, 39 insertions(+) > > > create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc > > > > > > diff --git a/tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc b/tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc > > > new file mode 100644 > > > index 000000000000..b414f0e3c646 > > > --- /dev/null > > > +++ b/tools/testing/selftests/ftrace/test.d/ftrace/func_stack_tracer.tc > > > @@ -0,0 +1,39 @@ > > > +#!/bin/sh > > > +# SPDX-License-Identifier: GPL-2.0 > > > +# description: ftrace - Max stack tracer > > > +# Test the basic function of max-stack usage tracing > > > + > > > +if [ ! -f stack_trace ]; then > > > + echo "Max stack tracer is not supported - please make CONFIG_STACK_TRACER=y" > > > + exit_unsupported > > > +fi > > > + > > > +echo > stack_trace_filter > > > +echo 0 > stack_max_size > > > +echo 1 > /proc/sys/kernel/stack_tracer_enabled > > > + > > > +: "Fork and wait for the first entry become !lock" > > > +timeout=10 > > > +while [ $timeout -ne 0 ]; do > > > + ( echo "forked" ) > > > + FL=`grep " 0)" stack_trace` > > > + echo $FL | grep -q "lock" || break; > > > + timeout=$((timeout - 1)) > > > +done > > > +echo 0 > /proc/sys/kernel/stack_tracer_enabled > > > + > > > +echo '*lock*' > stack_trace_filter > > > +test `cat stack_trace_filter | wc -l` -eq `grep lock stack_trace_filter | wc -l` > > > + > > > +echo 0 > stack_max_size > > > +echo 1 > /proc/sys/kernel/stack_tracer_enabled > > > > This test fails quite a bit because it doesn't guarantee that another > > stack trace gets in that is bigger, and we don't find the "lock". > > Hmm, maybe I misunderstand what is the stack_trace_filter. > I thought it filtered the function that triggered stack trace, > so the top of stack trace was always filtered function. > If not, what does this filter? Ah, I missed the filter part, no its correct, and actually found a bug ;-) By adding this patch, it works again: diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c index 4237eba4ef20..2b0d1ee3241c 100644 --- a/kernel/trace/trace_stack.c +++ b/kernel/trace/trace_stack.c @@ -111,7 +111,7 @@ check_stack(unsigned long ip, unsigned long *stack) stack_trace_max_size = this_size; stack_trace_max.nr_entries = 0; - stack_trace_max.skip = 3; + stack_trace_max.skip = 0; save_stack_trace(&stack_trace_max); -- Steve > > > > > + > > > +: "Fork and always the first entry including lock" > > > +timeout=10 > > > +while [ $timeout -ne 0 ]; do > > > + ( echo "forked" ) > > > + FL=`grep " 0)" stack_trace` > > > + echo $FL | grep -q "lock" > > > + timeout=$((timeout - 1)) > > > +done > > > +echo 0 > /proc/sys/kernel/stack_tracer_enabled > > > >
