hrtimer: prevent migration of per CPU hrtimers

Impact: per CPU hrtimers can be migrated from a dead CPU

The hrtimer code has no knowledge about per CPU timers, but we need to
prevent the migration of such timers and warn when such a timer is
active at migration time.

Explicitely mark the timers as per CPU and use a more understandable
mode descriptor for the interrupts safe unlocked callback mode, which
is used by hrtimer_sleeper and the scheduler code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 11 insertions, 3 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index bdd88df1b4e5..2f245fe63bda 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -47,14 +47,22 @@ enum hrtimer_restart {
  *      HRTIMER_CB_IRQSAFE:             Callback may run in hardirq context
  *      HRTIMER_CB_IRQSAFE_NO_RESTART:  Callback may run in hardirq context and
  *                                      does not restart the timer
- *      HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:  Callback must run in hardirq context
- *                                      Special mode for tick emultation
+ *      HRTIMER_CB_IRQSAFE_PERCPU:      Callback must run in hardirq context
+ *                                      Special mode for tick emulation and
+ *                                      scheduler timer. Such timers are per
+ *                                      cpu and not allowed to be migrated on
+ *                                      cpu unplug.
+ *      HRTIMER_CB_IRQSAFE_UNLOCKED:    Callback should run in hardirq context
+ *                                      with timer->base lock unlocked
+ *                                      used for timers which call wakeup to
+ *                                      avoid lock order problems with rq->lock
  */
 enum hrtimer_cb_mode {
         HRTIMER_CB_SOFTIRQ,
         HRTIMER_CB_IRQSAFE,
         HRTIMER_CB_IRQSAFE_NO_RESTART,
-        HRTIMER_CB_IRQSAFE_NO_SOFTIRQ,
+        HRTIMER_CB_IRQSAFE_PERCPU,
+        HRTIMER_CB_IRQSAFE_UNLOCKED,
 };
 
 /*