[PATCH v9 0/5] lib,kprobes: kretprobe scalability improvement

This patch series introduces a scalable and lockless ring-array based
object pool and replaces the original freelist (a LIFO queue based on
singly linked list) to improve scalability of kretprobed routines.

v9:
  1) objpool: raw_local_irq_save/restore added to prevent interruption

     To avoid possible ABA issues, we must ensure objpool_try_add_slot
     and objpool_try_add_slot are uninterruptible. If these operations
     are blocked or interrupted in the middle, other cores could overrun
     the same slot's ages[] of uint32, then after resuming back, the
     interrupted pop() or push() could see same value of ages[], which
     is a typical ABA problem though the possibility is small.

     The pair of pop()/push() costs about 8.53 cpu cycles, measured
     by IACA (Intel Architecture Code Analyzer). That is, on a 4Ghz
     core dedicated for pop() & push(), theoretically it would only
     need 8.53 seconds to overflow a 32bit value. Testings upon Intel
     i7-10700 (2.90GHz) cost 71.88 seconds to overrun a 32bit integer.

  2) codes improvements: thanks to Masami for the thorough inspection

v8:
  1) objpool: refcount added for objpool lifecycle management

wuqiang.matt (5):
  lib: objpool added: ring-array based lockless MPMC
  lib: objpool test module added
  kprobes: kretprobe scalability improvement with objpool
  kprobes: freelist.h removed
  MAINTAINERS: objpool added

 MAINTAINERS              |   7 +
 include/linux/freelist.h | 129 --------
 include/linux/kprobes.h  |  11 +-
 include/linux/objpool.h  | 174 ++++++++++
 include/linux/rethook.h  |  16 +-
 kernel/kprobes.c         |  93 +++---
 kernel/trace/fprobe.c    |  32 +-
 kernel/trace/rethook.c   |  90 +++--
 lib/Kconfig.debug        |  11 +
 lib/Makefile             |   4 +-
 lib/objpool.c            | 338 +++++++++++++++++++
 lib/test_objpool.c       | 689 +++++++++++++++++++++++++++++++++++++++
 12 files changed, 1320 insertions(+), 274 deletions(-)
 delete mode 100644 include/linux/freelist.h
 create mode 100644 include/linux/objpool.h
 create mode 100644 lib/objpool.c
 create mode 100644 lib/test_objpool.c

-- 
2.40.1