From 22a78be4123dce81d72c963a98b774b7d5e1f8e5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 8 Jul 2026 15:32:39 -0400 Subject: [PATCH 1/2] selftests/ftrace: Fix reading enabled_functions in add_remove_fprobe_module test The add_remove_fprobe_module test checks the number of functions added to the enabled_functions file to make sure that the functions added or removed is as expected. The issue is that it expects this file to be empty on start up. Now that systemd uses BPF that attaches to functions via ftrace, this file is not empty in several systems: # cat /sys/kernel/tracing/enabled_functions bpf_lsm_file_open (1) R D M tramp: ftrace_regs_caller+0x0/0x61 (call_direct_funcs+0x0/0x50) direct(jmp)-->bpf_trampoline_6442529439+0x0/0xe9 Change the test to read the number of lines in enabled_functions at the start of the test and subtract that from the value of the count for the checks within the test. Link: https://lore.kernel.org/r/20260708153239.055d56dd@gandalf.local.home Signed-off-by: Steven Rostedt Acked-by: Masami Hiramatsu (Google) Signed-off-by: Shuah Khan --- .../dynevent/add_remove_fprobe_module.tc | 27 ++++++++++++------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe_module.tc b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe_module.tc index 2915206777b6..89660a9adf44 100644 --- a/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe_module.tc +++ b/tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe_module.tc @@ -16,23 +16,32 @@ echo > dynamic_events FUNC1='foo_bar*' FUNC2='vfs_read' +:;: "Save enabled functions count" ;: +ecount=`cat enabled_functions | wc -l` + +count_enabled_functions() { + count=`cat enabled_functions | wc -l` + count=$(($count-$ecount)) + echo $count +} + :;: "Add an event on the test module" ;: echo "f:test1 $FUNC1" >> dynamic_events echo 1 > events/fprobes/test1/enable :;: "Ensure it is enabled" ;: -funcs=`cat enabled_functions | wc -l` +funcs=`count_enabled_functions` test $funcs -ne 0 :;: "Check the enabled_functions is cleared on unloading" ;: rmmod trace-events-sample -funcs=`cat enabled_functions | wc -l` +funcs=`count_enabled_functions` test $funcs -eq 0 :;: "Check it is kept clean" ;: modprobe trace-events-sample echo 1 > events/fprobes/test1/enable || echo "OK" -funcs=`cat enabled_functions | wc -l` +funcs=`count_enabled_functions` test $funcs -eq 0 :;: "Add another event not on the test module" ;: @@ -40,19 +49,19 @@ echo "f:test2 $FUNC2" >> dynamic_events echo 1 > events/fprobes/test2/enable :;: "Ensure it is enabled" ;: -ofuncs=`cat enabled_functions | wc -l` +ofuncs=`count_enabled_functions` test $ofuncs -ne 0 :;: "Disable and remove the first event" echo 0 > events/fprobes/test1/enable echo "-:fprobes/test1" >> dynamic_events -funcs=`cat enabled_functions | wc -l` +funcs=`count_enabled_functions` test $ofuncs -eq $funcs :;: "Disable and remove other events" ;: echo 0 > events/fprobes/enable echo > dynamic_events -funcs=`cat enabled_functions | wc -l` +funcs=`count_enabled_functions` test $funcs -eq 0 rmmod trace-events-sample @@ -63,12 +72,12 @@ echo "f:test1 $FUNC1" >> dynamic_events echo 1 > events/fprobes/test1/enable echo "f:test2 $FUNC2" >> dynamic_events echo 1 > events/fprobes/test2/enable -ofuncs=`cat enabled_functions | wc -l` +ofuncs=`count_enabled_functions` test $ofuncs -ne 0 :;: "Unload module (ftrace entry should be removed)" ;: rmmod trace-events-sample -funcs=`cat enabled_functions | wc -l` +funcs=`count_enabled_functions` test $funcs -ne 0 test $ofuncs -ne $funcs @@ -77,7 +86,7 @@ echo 0 > events/fprobes/test2/enable echo "-:fprobes/test2" >> dynamic_events :;: "Ensure ftrace is disabled." ;: -funcs=`cat enabled_functions | wc -l` +funcs=`count_enabled_functions` test $funcs -eq 0 echo 0 > events/fprobes/enable From c5c413534d40eb4c982f1794e62813f926aba747 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 8 Jul 2026 16:34:36 -0400 Subject: [PATCH 2/2] selftests/tracing: Have trigger-hist-poll.tc use sched_process_exit Currently trigger-hist-poll.tc uses sched_process_free to test the polling of the histogram file. The way it does that is to run sleep, then execute the poll.c code that polls on the sched_process_free for up to 4 seconds to test that when sleep triggers the sched_process_free trace event, it will update the histogram and wake the poll.c code up. The issue is that sched_process_free trace event is called by delayed_put_task_struct() which is called after a RCU grace period has ended. If CONFIG_RCU_LAZY is enabled, RCU callbacks are batched together and do not execute right away. This causes the delayed_put_task_struct() to be called after the poll.c function finishes and it will report an error that it did not wake up on the event. That's because the event didn't trigger during its wait time. Use sched_process_exit instead, which is called when a process exits and doesn't depend on RCU callbacks that may be delayed. Link: https://lore.kernel.org/r/20260708163436.058cc3df@gandalf.local.home Signed-off-by: Steven Rostedt Acked-by: Masami Hiramatsu (Google) Signed-off-by: Shuah Khan --- .../selftests/ftrace/test.d/trigger/trigger-hist-poll.tc | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc index 8d275e3238d9..04eb8546fc07 100644 --- a/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc +++ b/tools/testing/selftests/ftrace/test.d/trigger/trigger-hist-poll.tc @@ -1,7 +1,7 @@ #!/bin/sh # SPDX-License-Identifier: GPL-2.0 # description: event trigger - test poll wait on histogram -# requires: set_event events/sched/sched_process_free/trigger events/sched/sched_process_free/hist +# requires: set_event events/sched/sched_process_exit/trigger events/sched/sched_process_exit/hist # flags: instance POLL=${FTRACETEST_ROOT}/poll @@ -11,7 +11,7 @@ if [ ! -x ${POLL} ]; then exit_unresolved fi -EVENT=events/sched/sched_process_free/ +EVENT=events/sched/sched_process_exit/ # Check poll ops is supported. Before implementing poll on hist file, it # returns soon with POLLIN | POLLOUT, but not POLLPRI.