[ANNOUNCE] v4.11.12-rt12

Dear RT folks!

I'm pleased to announce the v4.11.12-rt12 patch set.

Changes since v4.11.12-rt11:

  - In the hrtimer/hotplug fix in the last release, there was one
    call path missed. Mike Galbraith reported it and sent a patch to
    handle it.

Known issues
	- There was a report regarding a deadlock within the rtmutex code.

The delta patch against v4.11.12-rt11 is appended below and can be found here:

     https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.11/incr/patch-4.11.12-rt11-rt12.patch.xz

You can get this release via the git tree at:

    git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v4.11.12-rt12

The RT patch against v4.11.12 can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.11/older/patch-4.11.12-rt12.patch.xz

The split quilt queue is available at:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.11/older/patches-4.11.12-rt12.tar.xz

Sebastian
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1779,7 +1779,7 @@ int hrtimers_prepare_cpu(unsigned int cpu)

 #ifdef CONFIG_HOTPLUG_CPU

-static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
+static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
 				struct hrtimer_clock_base *new_base)
 {
 	struct hrtimer *timer;
@@ -1809,15 +1809,19 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
 	}
 #ifdef CONFIG_PREEMPT_RT_BASE
 	list_splice_tail(&old_base->expired, &new_base->expired);
-	if (!list_empty(&new_base->expired))
-		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+	/*
+	 * Tell the caller to raise HRTIMER_SOFTIRQ.  We can't safely
+	 * acquire ktimersoftd->pi_lock while the base lock is held.
+	 */
+	return !list_empty(&new_base->expired);
 #endif
+	return 0;
 }

 int hrtimers_dead_cpu(unsigned int scpu)
 {
 	struct hrtimer_cpu_base *old_base, *new_base;
-	int i;
+	int i, raise = 0;

 	BUG_ON(cpu_online(scpu));
 	tick_cancel_sched_timer(scpu);
@@ -1833,13 +1837,16 @@ int hrtimers_dead_cpu(unsigned int scpu)
 	raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
-		migrate_hrtimer_list(&old_base->clock_base[i],
-				     &new_base->clock_base[i]);
+		raise |= migrate_hrtimer_list(&old_base->clock_base[i],
+					      &new_base->clock_base[i]);
 	}

 	raw_spin_unlock(&old_base->lock);
 	raw_spin_unlock(&new_base->lock);

+	if (raise)
+		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
+
 	/* Check, if we got expired work to do */
 	__hrtimer_peek_ahead_timers();
 	local_irq_enable();
diff --git a/localversion-rt b/localversion-rt
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt11
+-rt12

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

3 files changed, 71 insertions, 1 deletions

diff --git a/patches/kernel-hrtimer-hotplug-don-t-wake-ktimersoftd-while-.patch b/patches/kernel-hrtimer-hotplug-don-t-wake-ktimersoftd-while-.patch
new file mode 100644
index 00000000000000..925c2af1942ebf
--- /dev/null
+++ b/patches/kernel-hrtimer-hotplug-don-t-wake-ktimersoftd-while-.patch
@@ -0,0 +1,69 @@
+From 4ca8658769126558b04a1d78b7d6bee389bfa24b Mon Sep 17 00:00:00 2001
+From: Mike Galbraith <efault@gmx.de>
+Date: Sun, 3 Sep 2017 04:48:10 +0200
+Subject: [PATCH] kernel/hrtimer/hotplug: don't wake ktimersoftd while holding
+ the hrtimer base lock
+
+kernel/hrtimer: don't wakeup a process while holding the hrtimer base lock
+missed a path, namely hrtimers_dead_cpu() -> migrate_hrtimer_list().  Defer
+raising softirq until after base lock has been released there as well.
+
+Signed-off-by: Mike Galbraith <efault@gmx.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/time/hrtimer.c |   19 +++++++++++++------
+ 1 file changed, 13 insertions(+), 6 deletions(-)
+
+--- a/kernel/time/hrtimer.c
++++ b/kernel/time/hrtimer.c
+@@ -1725,7 +1725,7 @@ int hrtimers_prepare_cpu(unsigned int cp
+ 
+ #ifdef CONFIG_HOTPLUG_CPU
+ 
+-static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
++static int migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
+ 				struct hrtimer_clock_base *new_base)
+ {
+ 	struct hrtimer *timer;
+@@ -1755,15 +1755,19 @@ static void migrate_hrtimer_list(struct
+ 	}
+ #ifdef CONFIG_PREEMPT_RT_BASE
+ 	list_splice_tail(&old_base->expired, &new_base->expired);
+-	if (!list_empty(&new_base->expired))
+-		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
++	/*
++	 * Tell the caller to raise HRTIMER_SOFTIRQ.  We can't safely
++	 * acquire ktimersoftd->pi_lock while the base lock is held.
++	 */
++	return !list_empty(&new_base->expired);
+ #endif
++	return 0;
+ }
+ 
+ int hrtimers_dead_cpu(unsigned int scpu)
+ {
+ 	struct hrtimer_cpu_base *old_base, *new_base;
+-	int i;
++	int i, raise = 0;
+ 
+ 	BUG_ON(cpu_online(scpu));
+ 	tick_cancel_sched_timer(scpu);
+@@ -1779,13 +1783,16 @@ int hrtimers_dead_cpu(unsigned int scpu)
+ 	raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
+ 
+ 	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
+-		migrate_hrtimer_list(&old_base->clock_base[i],
+-				     &new_base->clock_base[i]);
++		raise |= migrate_hrtimer_list(&old_base->clock_base[i],
++					      &new_base->clock_base[i]);
+ 	}
+ 
+ 	raw_spin_unlock(&old_base->lock);
+ 	raw_spin_unlock(&new_base->lock);
+ 
++	if (raise)
++		raise_softirq_irqoff(HRTIMER_SOFTIRQ);
++
+ 	/* Check, if we got expired work to do */
+ 	__hrtimer_peek_ahead_timers();
+ 	local_irq_enable();
diff --git a/patches/localversion.patch b/patches/localversion.patch
index 58842b503a2712..12bd473a33f5b0 100644
--- a/patches/localversion.patch
+++ b/patches/localversion.patch
@@ -10,4 +10,4 @@ Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
 --- /dev/null
 +++ b/localversion-rt
 @@ -0,0 +1 @@
-+-rt11
++-rt12
diff --git a/patches/series b/patches/series
index 8dac6fa0f250ee..0985cc1292d05d 100644
--- a/patches/series
+++ b/patches/series
@@ -397,6 +397,7 @@ tick-broadcast--Make-hrtimer-irqsafe.patch
 timer-hrtimer-check-properly-for-a-running-timer.patch
 kernel-hrtimer-migrate-deferred-timer-on-CPU-down.patch
 kernel-hrtimer-don-t-wakeup-a-process-while-holding-.patch
+kernel-hrtimer-hotplug-don-t-wake-ktimersoftd-while-.patch
 
 # POSIX-CPU-TIMERS
 posix-timers-thread-posix-cpu-timers-on-rt.patch