[tip:timers/core] hrtimer: Make enqueue mode check work on RT

[tip-bot for Sebastian Andrzej Siewior <tipbot@xxxxxxxxx>]

Commit-ID:  14429655b5e0cc293543bba8f8d6c3661e1ea033
Gitweb:     https://git.kernel.org/tip/14429655b5e0cc293543bba8f8d6c3661e1ea033
Author:     Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate: Tue, 30 Jul 2019 20:15:25 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Thu, 1 Aug 2019 17:43:17 +0200

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@xxxxxxxxxxxxx>

---
 include/linux/hrtimer.h | 3 +++
 kernel/time/hrtimer.c   | 9 +++++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 15c2ba6b6316..7d0d0a36a8f4 100644
--- 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 dab1ea1a99d0..0ace301a56f4 100644
--- 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);
 }