tree 6a8def137182bfaff4380045f564c170cb454b85
parent 00164f477f065a0faaed7f2ca8f1c724c99b6fe1
parent 03877039863be021a19fda307136657bb6d61f75
author Linus Torvalds <torvalds@linux-foundation.org> 1711230565 -0700
committer Linus Torvalds <torvalds@linux-foundation.org> 1711230565 -0700
mergetag object 03877039863be021a19fda307136657bb6d61f75
 type commit
 tag timers-urgent-2024-03-23
 tagger Thomas Gleixner <tglx@linutronix.de> 1711223423 +0100
 
 Two regression fixes for the timer and timer migration code:
 
   1) Prevent endless timer requeuing which is caused by two CPUs racing out
      of idle. This happens when the last CPU goes idle and therefore has to
      ensure to expire the pending global timers and some other CPU come out
      of idle at the same time and the other CPU wins the race and expires
      the global queue. This causes the last CPU to chase ghost timers
      forever and reprogramming it's clockevent device endlessly.
 
      Cure this by re-evaluating the wakeup time unconditionally.
 
   2) The split into local (pinned) and global timers in the timer wheel
      caused a regression for NOHZ full as it broke the idle tracking of
      global timers. On NOHZ full this prevents an self IPI being sent which
      in turn causes the timer to be not programmed and not being expired on
      time.
 
      Restore the idle tracking for the global timer base so that the self
      IPI condition for NOHZ full is working correctly again.
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Merge tag 'timers-urgent-2024-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer fixes from Thomas Gleixner:
 "Two regression fixes for the timer and timer migration code:

   - Prevent endless timer requeuing which is caused by two CPUs racing
     out of idle. This happens when the last CPU goes idle and therefore
     has to ensure to expire the pending global timers and some other
     CPU come out of idle at the same time and the other CPU wins the
     race and expires the global queue. This causes the last CPU to
     chase ghost timers forever and reprogramming it's clockevent device
     endlessly.

     Cure this by re-evaluating the wakeup time unconditionally.

   - The split into local (pinned) and global timers in the timer wheel
     caused a regression for NOHZ full as it broke the idle tracking of
     global timers. On NOHZ full this prevents an self IPI being sent
     which in turn causes the timer to be not programmed and not being
     expired on time.

     Restore the idle tracking for the global timer base so that the
     self IPI condition for NOHZ full is working correctly again"

* tag 'timers-urgent-2024-03-23' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timers: Fix removed self-IPI on global timer's enqueue in nohz_full
  timers/migration: Fix endless timer requeue after idle interrupts