Dear RT folks!
I'm pleased to announce the v4.11.12-rt15 patch set.
Changes since v4.11.12-rt14:
- Programmed wake ups (nanosleep, clock_nanosleep, …) by a task with
RT priority will still be carried out in the hardirq context
(nothing changes). If it is programmed by task with a normal
priority then the wake up will be carried out in the softirq
context via the ktimersoftd thread.
The advantage is that multiple wake ups of non-RT tasks won't
disturb the RT task. Reported by Gratian Crisan.
- Paul Gortmaker reported splat during boot when TSC (on x86) becomes
unstable and kernel switches to an alternative. This has been fixed
by cherry-picking a patch from upstream.
- After the hrtimer rework, certain wake ups (like those programmed in
the past using the softirq context) won't fire. Reported by Mike
Galbraith, patched by Anna-Maria Gleixner.
- After the hrtimer rework, wake ups using CLOCK_REALTIME and a
relative delay were affected by clock_settime() (they should have
not been). Reported by Mike Galbraith.
Known issues
None
The delta patch against v4.11.12-rt14 is appended below and can be found here:
https://cdn.kernel.org/pub/linux/kernel/projects/rt/4.11/incr/patch-4.11.12-rt14-rt15.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-rt15
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-rt15.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-rt15.tar.xz
Sebastian
diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c
--- a/kernel/sched/clock.c
+++ b/kernel/sched/clock.c
@@ -124,6 +124,12 @@ int sched_clock_stable(void)
return static_branch_likely(&__sched_clock_stable);
}
+static void __scd_stamp(struct sched_clock_data *scd)
+{
+ scd->tick_gtod = ktime_get_ns();
+ scd->tick_raw = sched_clock();
+}
+
static void __set_sched_clock_stable(void)
{
struct sched_clock_data *scd;
@@ -148,8 +154,37 @@ static void __set_sched_clock_stable(void)
tick_dep_clear(TICK_DEP_BIT_CLOCK_UNSTABLE);
}
+/*
+ * If we ever get here, we're screwed, because we found out -- typically after
+ * the fact -- that TSC wasn't good. This means all our clocksources (including
+ * ktime) could have reported wrong values.
+ *
+ * What we do here is an attempt to fix up and continue sort of where we left
+ * off in a coherent manner.
+ *
+ * The only way to fully avoid random clock jumps is to boot with:
+ * "tsc=unstable".
+ */
static void __sched_clock_work(struct work_struct *work)
{
+ struct sched_clock_data *scd;
+ int cpu;
+
+ /* take a current timestamp and set 'now' */
+ preempt_disable();
+ scd = this_scd();
+ __scd_stamp(scd);
+ scd->clock = scd->tick_gtod + __gtod_offset;
+ preempt_enable();
+
+ /* clone to all CPUs */
+ for_each_possible_cpu(cpu)
+ per_cpu(sched_clock_data, cpu) = *scd;
+
+ printk(KERN_INFO "sched_clock: Marking unstable (%lld, %lld)<-(%lld, %lld)\n",
+ scd->tick_gtod, __gtod_offset,
+ scd->tick_raw, __sched_clock_offset);
+
static_branch_disable(&__sched_clock_stable);
}
@@ -157,27 +192,11 @@ static DECLARE_WORK(sched_clock_work, __sched_clock_work);
static void __clear_sched_clock_stable(void)
{
- struct sched_clock_data *scd = this_scd();
-
- /*
- * Attempt to make the stable->unstable transition continuous.
- *
- * Trouble is, this is typically called from the TSC watchdog
- * timer, which is late per definition. This means the tick
- * values can already be screwy.
- *
- * Still do what we can.
- */
- __gtod_offset = (scd->tick_raw + __sched_clock_offset) - (scd->tick_gtod);
-
- printk(KERN_INFO "sched_clock: Marking unstable (%lld, %lld)<-(%lld, %lld)\n",
- scd->tick_gtod, __gtod_offset,
- scd->tick_raw, __sched_clock_offset);
+ if (!sched_clock_stable())
+ return;
tick_dep_set(TICK_DEP_BIT_CLOCK_UNSTABLE);
-
- if (sched_clock_stable())
- schedule_work(&sched_clock_work);
+ schedule_work(&sched_clock_work);
}
void clear_sched_clock_stable(void)
@@ -364,8 +383,7 @@ void sched_clock_tick(void)
* XXX arguably we can skip this if we expose tsc_clocksource_reliable
*/
scd = this_scd();
- scd->tick_raw = sched_clock();
- scd->tick_gtod = ktime_get_ns();
+ __scd_stamp(scd);
if (!sched_clock_stable() && likely(sched_clock_running))
sched_clock_local(scd);
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -562,8 +562,14 @@ static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
ktime_t *offs_tai = &base->clock_base[HRTIMER_BASE_TAI].offset;
- return ktime_get_update_offsets_now(&base->clock_was_set_seq,
+ ktime_t now = ktime_get_update_offsets_now(&base->clock_was_set_seq,
offs_real, offs_boot, offs_tai);
+
+ base->clock_base[HRTIMER_BASE_REALTIME_SOFT].offset = *offs_real;
+ base->clock_base[HRTIMER_BASE_BOOTTIME_SOFT].offset = *offs_boot;
+ base->clock_base[HRTIMER_BASE_TAI_SOFT].offset = *offs_tai;
+
+ return now;
}
/*
@@ -1252,6 +1258,8 @@ static void __hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
clock_id = CLOCK_MONOTONIC;
else if (clock_id == CLOCK_REALTIME_SOFT)
clock_id = CLOCK_MONOTONIC_SOFT;
+ else if (clock_id == CLOCK_REALTIME_HARD)
+ clock_id = CLOCK_MONOTONIC_HARD;
}
base = hrtimer_clockid_to_base(clock_id);
@@ -1622,14 +1630,31 @@ static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
return HRTIMER_NORESTART;
}
+#ifdef CONFIG_PREEMPT_RT_FULL
+static bool task_is_elevated(struct task_struct *tsk)
+{
+ int policy = tsk->policy;
+
+ if (policy == SCHED_FIFO || policy == SCHED_RR)
+ return true;
+ if (policy == SCHED_DEADLINE)
+ return true;
+ return false;
+}
+#endif
+
static void __hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
clockid_t clock_id,
enum hrtimer_mode mode,
struct task_struct *task)
{
#ifdef CONFIG_PREEMPT_RT_FULL
- if (!(clock_id & HRTIMER_BASE_SOFT_MASK))
- clock_id |= HRTIMER_BASE_HARD_MASK;
+ if (!(clock_id & (HRTIMER_BASE_HARD_MASK | HRTIMER_BASE_SOFT_MASK))) {
+ if (task_is_elevated(current) || system_state != SYSTEM_RUNNING)
+ clock_id |= HRTIMER_BASE_HARD_MASK;
+ else
+ clock_id |= HRTIMER_BASE_SOFT_MASK;
+ }
#endif
__hrtimer_init(&sl->timer, clock_id, mode);
sl->timer.function = hrtimer_wakeup;
diff --git a/localversion-rt b/localversion-rt
--- a/localversion-rt
+++ b/localversion-rt
@@ -1 +1 @@
--rt14
+-rt15
--
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