A samll set of timer related fixes:

 - Plug a race between rearm and process tick in the posix CPU timers code

 - Make the optimization to avoid recalculation of the next timer interrupt
   work correctly when there are no timers pending.
Merge branch 'timers/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into timers/urgent

Pull dyntick fixes from Frederic Weisbecker:

  - Fix a rearm race in the posix cpu timer code
  - Handle get_next_timer_interrupt() correctly when no timers are pending

Link: https://lore.kernel.org/r/20210715104218.81276-1-frederic@kernel.org