timers-nohz-2021-06-28

 - Micro-optimize tick_nohz_full_cpu()

 - Optimize idle exit tick restarts to be less eager

 - Optimize tick_nohz_dep_set_task() to only wake up
   a single CPU. This reduces IPIs and interruptions
   on nohz_full CPUs.

 - Optimize tick_nohz_dep_set_signal() in a similar
   fashion.

 - Skip IPIs in tick_nohz_kick_task() when trying
   to kick a non-running task.

 - Micro-optimize tick_nohz_task_switch() IRQ flags
   handling to reduce context switching costs.

 - Misc cleanups and fixes

Signed-off-by: Ingo Molnar <mingo@kernel.org>