Hi Greg! Months ago you picked up mainline commit a2b6e99d8a6
("drm/i915: Disable DC states for all commits") for the 6.1.23 release
as commit 0fc6fea41c71. It causes issues vor a few people (at least
three, two of which are CCed) -- apparently because it depends on some
change that wasn't picked up for 6.1.y. This is known for a while now,
but nobody has yet found which change that is (Al found something that
worked for him, but that didn't work for others). For the whole story
skim this ticket:
https://gitlab.freedesktop.org/drm/intel/-/issues/8419
I wonder if it might be better if you revert that commit for 6.0.y; I
asked already in the ticket if this is likely to cause regressions for
users of 6.0.y, but got no answer from the i915 devs (or did I miss
something?). :-/
Ciao, Thorsten
From: Frederic Weisbecker <frederic(a)kernel.org>
[ Upstream commit a1ff03cd6fb9c501fff63a4a2bface9adcfa81cd ]
tick: Detect and fix jiffies update stall
On some rare cases, the timekeeper CPU may be delaying its jiffies
update duty for a while. Known causes include:
* The timekeeper is waiting on stop_machine in a MULTI_STOP_DISABLE_IRQ
or MULTI_STOP_RUN state. Disabled interrupts prevent from timekeeping
updates while waiting for the target CPU to complete its
stop_machine() callback.
* The timekeeper vcpu has VMEXIT'ed for a long while due to some overload
on the host.
Detect and fix these situations with emergency timekeeping catchups.
Original-patch-by: Paul E. McKenney <paulmck(a)kernel.org>
Signed-off-by: Frederic Weisbecker <frederic(a)kernel.org>
Cc: Thomas Gleixner <tglx(a)linutronix.de>
Signed-off-by: Joel Fernandes (Google) <joel(a)joelfernandes.org>
---
kernel/time/tick-sched.c | 17 +++++++++++++++++
kernel/time/tick-sched.h | 4 ++++
2 files changed, 21 insertions(+)
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f42d0776bc84..7701c720dc1f 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -180,6 +180,8 @@ static ktime_t tick_init_jiffy_update(void)
return period;
}
+#define MAX_STALLED_JIFFIES 5
+
static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
{
int cpu = smp_processor_id();
@@ -207,6 +209,21 @@ static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
if (tick_do_timer_cpu == cpu)
tick_do_update_jiffies64(now);
+ /*
+ * If jiffies update stalled for too long (timekeeper in stop_machine()
+ * or VMEXIT'ed for several msecs), force an update.
+ */
+ if (ts->last_tick_jiffies != jiffies) {
+ ts->stalled_jiffies = 0;
+ ts->last_tick_jiffies = READ_ONCE(jiffies);
+ } else {
+ if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) {
+ tick_do_update_jiffies64(now);
+ ts->stalled_jiffies = 0;
+ ts->last_tick_jiffies = READ_ONCE(jiffies);
+ }
+ }
+
if (ts->inidle)
ts->got_idle_tick = 1;
}
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index d952ae393423..504649513399 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -49,6 +49,8 @@ enum tick_nohz_mode {
* @timer_expires_base: Base time clock monotonic for @timer_expires
* @next_timer: Expiry time of next expiring timer for debugging purpose only
* @tick_dep_mask: Tick dependency mask - is set, if someone needs the tick
+ * @last_tick_jiffies: Value of jiffies seen on last tick
+ * @stalled_jiffies: Number of stalled jiffies detected across ticks
*/
struct tick_sched {
struct hrtimer sched_timer;
@@ -77,6 +79,8 @@ struct tick_sched {
u64 next_timer;
ktime_t idle_expires;
atomic_t tick_dep_mask;
+ unsigned long last_tick_jiffies;
+ unsigned int stalled_jiffies;
};
extern struct tick_sched *tick_get_tick_sched(int cpu);
--
2.41.0.640.ga95def55d0-goog