selftests/ftrace: Add a test case for repeating register/unregister fprobe

This test case repeats define and undefine the fprobe dynamic event to
ensure that the fprobe does not cause any issue with such operations.

Cc: Alexei Starovoitov <[e-mail]>
Cc: Florent Revest <[e-mail]>
Cc: Martin KaFai Lau <[e-mail]>
Cc: bpf <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Alan Maguire <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Link: https://lore.kernel.org/173519009398.391279.4625924605120064761.stgit@devnote2
Signed-off-by: Masami Hiramatsu (Google) <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

tools/testing/selftests/ftrace/test.d/dynevent/add_remove_fprobe_repeat.tc

···
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+# description: Generic dynamic event - Repeating add/remove fprobe events
+# requires: dynamic_events "f[:[<group>/][<event>]] <func-name>[%return] [<args>]":README
+
+echo 0 > events/enable
+echo > dynamic_events
+
+PLACE=$FUNCTION_FORK
+REPEAT_TIMES=64
+
+for i in `seq 1 $REPEAT_TIMES`; do
+  echo "f:myevent $PLACE" >> dynamic_events
+  grep -q myevent dynamic_events
+  test -d events/fprobes/myevent
+  echo > dynamic_events
+done
+
+clear_trace