[patch V2 00/17] posix-timers: Rework the global hash table and provide a sane mechanism for CRIU

[Thomas Gleixner <tglx@linutronix.de>]

This is a follow up on V1 of this work, which can be found here:

     https://lore.kernel.org/all/20250224095736.145530367@linutronix.de

It addresses the scalability problem of the posix timer hash and provides a
performant mechanism to restore Posix timers with a given ID along with a
couple of preperatory cleanups and enhancements. More details about
implementation choices are in the change logs and the cover letter of V1.

Changes vs. V1:

  - Simplify the timer removal cleanup - PeterZ
  - Use guards consistently - PeterZ
  - Switch to jhash32()
  - Avoid false sharing by reordering struct k_itimer
  - Advance the ID counter when restoring
  - A few additional cleanups

The series survives all posix timer tests and did not show any regressions
so far.

The series is based on:

    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip timers/core

and is also available from git:

    git://git.kernel.org/pub/scm/linux/kernel/git/tglx/devel.git timers/posix

Thanks,

	tglx
---
Eric Dumazet (3):
      posix-timers: Initialise timer before adding it to the hash table
      posix-timers: Add cond_resched() to posix_timer_add() search loop
      posix-timers: Make signal_struct::next_posix_timer_id an atomic_t

Peter Zijlstra (1):
      posix-timers: Make lock_timer() use guard()

Thomas Gleixner (13):
      posix-timers: Cleanup includes
      posix-timers: Remove a few paranoid warnings
      posix-timers: Remove SLAB_PANIC from kmem cache
      posix-timers: Use guards in a few places
      posix-timers: Simplify lock/unlock_timer()
      posix-timers: Rework timer removal
      posix-timers: Improve hash table performance
      posix-timers: Switch to jhash32()
      posix-timers: Avoid false cacheline sharing
      posix-timers: Make per process list RCU safe
      posix-timers: Don't iterate /proc/$PID/timers with sighand::siglock held
      posix-timers: Provide a mechanism to allocate a given timer ID
      selftests/timers/posix-timers: Add a test for exact allocation mode

 fs/proc/base.c                                |   48 --
 include/linux/cleanup.h                       |   22 -
 include/linux/posix-timers.h                  |   30 +
 include/linux/sched/signal.h                  |    3 
 include/uapi/linux/prctl.h                    |   10 
 kernel/signal.c                               |    2 
 kernel/sys.c                                  |    5 
 kernel/time/posix-timers.c                    |  530 +++++++++++++-------------
 tools/testing/selftests/timers/posix_timers.c |   60 ++
 9 files changed, 403 insertions(+), 307 deletions(-)