hrtimers: prepare full preemption

Make cancellation of a running callback in softirq context safe
against preemption.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 32 insertions, 1 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index 7c4ee68..86adf2b 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -871,6 +871,32 @@ u64 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
 }
 EXPORT_SYMBOL_GPL(hrtimer_forward);
 
+#ifdef CONFIG_PREEMPT_RT_BASE
+# define wake_up_timer_waiters(b)	wake_up(&(b)->wait)
+
+/**
+ * hrtimer_wait_for_timer - Wait for a running timer
+ *
+ * @timer:	timer to wait for
+ *
+ * The function waits in case the timers callback function is
+ * currently executed on the waitqueue of the timer base. The
+ * waitqueue is woken up after the timer callback function has
+ * finished execution.
+ */
+void hrtimer_wait_for_timer(const struct hrtimer *timer)
+{
+	struct hrtimer_clock_base *base = timer->base;
+
+	if (base && base->cpu_base && !hrtimer_hres_active(base->cpu_base))
+		wait_event(base->cpu_base->wait,
+				!(timer->state & HRTIMER_STATE_CALLBACK));
+}
+
+#else
+# define wake_up_timer_waiters(b)	do { } while (0)
+#endif
+
 /*
  * enqueue_hrtimer - internal function to (re)start a timer
  *
@@ -1123,7 +1149,7 @@ int hrtimer_cancel(struct hrtimer *timer)
 
 		if (ret >= 0)
 			return ret;
-		cpu_relax();
+		hrtimer_wait_for_timer(timer);
 	}
 }
 EXPORT_SYMBOL_GPL(hrtimer_cancel);
@@ -1533,6 +1559,8 @@ void hrtimer_run_queues(void)
 		}
 		raw_spin_unlock(&cpu_base->lock);
 	}
+
+	wake_up_timer_waiters(cpu_base);
 }
 
 /*
@@ -1693,6 +1721,9 @@ static void init_hrtimers_cpu(int cpu)
 	}
 
 	hrtimer_init_hres(cpu_base);
+#ifdef CONFIG_PREEMPT_RT_BASE
+	init_waitqueue_head(&cpu_base->wait);
+#endif
 }
 
 #ifdef CONFIG_HOTPLUG_CPU