[PATCH v9 2/6] selftests/ftrace: Add clear_dynamic_events() to test cases

[Steven Rostedt <rostedt@goodmis.org>]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Add a function to remove all dynamic events from the tracing directory. It
requires a loop as some of the dynamic events may depend on others being
removed first. Also add a safety that prevents it from looping infinitely
due to a bug where an event never gets removed.

Link: https://lkml.kernel.org/r/20210819152825.348941368@goodmis.org

Cc: Shuah Khan <shuah@kernel.org>
Cc: Shuah Khan <skhan@linuxfoundation.org>
Cc: linux-kselftest@vger.kernel.org
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 .../testing/selftests/ftrace/test.d/functions | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tools/testing/selftests/ftrace/test.d/functions b/tools/testing/selftests/ftrace/test.d/functions
index a6fac927ee82..f68d336b961b 100644
--- a/tools/testing/selftests/ftrace/test.d/functions
+++ b/tools/testing/selftests/ftrace/test.d/functions
@@ -83,6 +83,27 @@ clear_synthetic_events() { # reset all current synthetic events
     done
 }
 
+clear_dynamic_events() { # reset all current dynamic events
+    again=1
+    stop=1
+    # loop mulitple times as some events require other to be removed first
+    while [ $again -eq 1 ]; do
+	stop=$((stop+1))
+	# Prevent infinite loops
+	if [ $stop -gt 10 ]; then
+	    break;
+	fi
+	again=2
+	grep -v '^#' dynamic_events|
+	while read line; do
+	    del=`echo $line | sed -e 's/^.\([^ ]*\).*/-\1/'`
+	    if ! echo "$del" >> dynamic_events; then
+		again=1
+	    fi
+	done
+    done
+}
+
 initialize_ftrace() { # Reset ftrace to initial-state
 # As the initial state, ftrace will be set to nop tracer,
 # no events, no triggers, no filters, no function filters,
@@ -93,6 +114,7 @@ initialize_ftrace() { # Reset ftrace to initial-state
     reset_events_filter
     reset_ftrace_filter
     disable_events
+    clear_dynamic_events
     [ -f set_event_pid ] && echo > set_event_pid
     [ -f set_ftrace_pid ] && echo > set_ftrace_pid
     [ -f set_ftrace_notrace ] && echo > set_ftrace_notrace
-- 
2.30.2