1. 01 2月, 2017 30 次提交
  2. 31 1月, 2017 9 次提交
  3. 30 1月, 2017 1 次提交
    • S
      sched/rt: Add a missing rescheduling point · 619bd4a7
      Sebastian Andrzej Siewior 提交于
      Since the change in commit:
      
        fd7a4bed ("sched, rt: Convert switched_{from, to}_rt() / prio_changed_rt() to balance callbacks")
      
      ... we don't reschedule a task under certain circumstances:
      
      Lets say task-A, SCHED_OTHER, is running on CPU0 (and it may run only on
      CPU0) and holds a PI lock. This task is removed from the CPU because it
      used up its time slice and another SCHED_OTHER task is running. Task-B on
      CPU1 runs at RT priority and asks for the lock owned by task-A. This
      results in a priority boost for task-A. Task-B goes to sleep until the
      lock has been made available. Task-A is already runnable (but not active),
      so it receives no wake up.
      
      The reality now is that task-A gets on the CPU once the scheduler decides
      to remove the current task despite the fact that a high priority task is
      enqueued and waiting. This may take a long time.
      
      The desired behaviour is that CPU0 immediately reschedules after the
      priority boost which made task-A the task with the lowest priority.
      Suggested-by: NPeter Zijlstra <peterz@infradead.org>
      Signed-off-by: NSebastian Andrzej Siewior <bigeasy@linutronix.de>
      Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Mike Galbraith <efault@gmx.de>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Fixes: fd7a4bed ("sched, rt: Convert switched_{from, to}_rt() prio_changed_rt() to balance callbacks")
      Link: http://lkml.kernel.org/r/20170124144006.29821-1-bigeasy@linutronix.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      619bd4a7