lib: test_objpool: make global variables static

Kernel test robot reported build warnings that structures g_ot_sync_ops,
g_ot_async_ops and g_testcases should be static. These definitions are
only used in test_objpool.c, so make them static

Link: https://lore.kernel.org/all/20231108012248.313574-1-wuqiang.matt@bytedance.com/

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202311071229.WGrWUjM1-lkp@intel.com/

Signed-off-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

kprobes: unused header files removed

As kernel test robot reported, lib/test_objpool.c (trace:probes/for-next)
has linux/version.h included, but version.h is not used at all. Then more
unused headers are found in test_objpool.c and rethook.c, and all of them
should be removed.

Link: https://lore.kernel.org/all/20231023112245.6112-1-wuqiang.matt@bytedance.com/

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202310191512.vvypKU5Z-lkp@intel.com/
Signed-off-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

lib: objpool test module added

The test_objpool module (test_objpool) will run several testcases
for objpool stress and performance evaluation. Each testcase will
have all available cpu cores involved to create a situation of high
parallel and high contention.

As of now there are 5 groups and 5 * 2 testcases in total:

1) group 1: synchronous mode
objpool is managed synchronously, that is, all objects are to be
reclaimed before objpool finalization and the objpool owner makes
sure of it. All threads on different cores run in the same pace
2) group 2: synchronous mode + hrtimer
this case have 2 customers: normal threads and hrtimer softirqs
3) group 3: synchronous + overrun mode
This test group is mainly for performance evaluation of missing
cases when pre-allocated objects are less than the requested
4) group 4: asynchronous mode
This case is just an emulation of kretprobe, with refcount used
to control the objpool lifecycle
5) group 5: asynchronous mode with hrtimer
hrtimer softirq is introduced to stress async objpool operations

Link: https://lore.kernel.org/all/20231017135654.82270-3-wuqiang.matt@bytedance.com/

Signed-off-by: wuqiang.matt <wuqiang.matt@bytedance.com>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>