hrtimer: Make enqueue mode check work on RT

hrtimer_start_range_ns() has a WARN_ONCE() which verifies that a timer
which is marker for softirq expiry is not queued in the hard interrupt base
and vice versa.

When PREEMPT_RT is enabled, timers which are not explicitely marked to
expire in hard interrupt context are deferrred to the soft interrupt. So
the regular check would trigger.

Change the check, so when PREEMPT_RT is enabled, it is verified that the
timers marked for hard interrupt expiry are not tried to be queued for soft
interrupt expiry or any of the unmarked and softirq marked is tried to be
expired in hard interrupt context.

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

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 15c2ba6b6316548d3f1bf65428283c4e9a402723..7d0d0a36a8f492431d62ba845ce7a77ae348c3ce 100644 (file)
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -107,6 +107,8 @@ enum hrtimer_restart {
  * @state:     state information (See bit values above)
  * @is_rel:    Set if the timer was armed relative
  * @is_soft:   Set if hrtimer will be expired in soft interrupt context.
+ * @is_hard:   Set if hrtimer will be expired in hard interrupt context
+ *             even on RT.
  *
  * The hrtimer structure must be initialized by hrtimer_init()
  */
@@ -118,6 +120,7 @@ struct hrtimer {
        u8                              state;
        u8                              is_rel;
        u8                              is_soft;
+       u8                              is_hard;
 };
 
 /**

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index dab1ea1a99d02f43f768f0d995ec4283115f942a..0ace301a56f46d71d9590ef1fe55af4e412e3a0d 100644 (file)
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1107,9 +1107,13 @@ void hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,
 
        /*
         * Check whether the HRTIMER_MODE_SOFT bit and hrtimer.is_soft
-        * match.
+        * match on CONFIG_PREEMPT_RT = n. With PREEMPT_RT check the hard
+        * expiry mode because unmarked timers are moved to softirq expiry.
         */
-       WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
+       if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+               WARN_ON_ONCE(!(mode & HRTIMER_MODE_SOFT) ^ !timer->is_soft);
+       else
+               WARN_ON_ONCE(!(mode & HRTIMER_MODE_HARD) ^ !timer->is_hard);
 
        base = lock_hrtimer_base(timer, &flags);
 
@@ -1288,6 +1292,7 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
 
        base += hrtimer_clockid_to_base(clock_id);
        timer->is_soft = softtimer;
+       timer->is_hard = !softtimer;
        timer->base = &cpu_base->clock_base[base];
        timerqueue_init(&timer->node);
 }