mirror of
https://github.com/linuxkit/linuxkit.git
synced 2025-07-24 03:15:36 +00:00
95 lines
3.5 KiB
Diff
95 lines
3.5 KiB
Diff
From 748812cb4f5a3b85cb2ba72c6edb68e390137b84 Mon Sep 17 00:00:00 2001
|
|
From: Anna-Maria Gleixner <anna-maria@linutronix.de>
|
|
Date: Wed, 20 Dec 2017 17:13:08 +0100
|
|
Subject: [PATCH 035/418] hrtimer: Unify handling of hrtimer remove
|
|
|
|
When the first hrtimer on the current CPU is removed,
|
|
hrtimer_force_reprogram() is invoked but only when
|
|
CONFIG_HIGH_RES_TIMERS=y and hrtimer_cpu_base.hres_active is set.
|
|
|
|
hrtimer_force_reprogram() updates hrtimer_cpu_base.expires_next and
|
|
reprograms the clock event device. When CONFIG_HIGH_RES_TIMERS=y and
|
|
hrtimer_cpu_base.hres_active is set, a pointless hrtimer interrupt can be
|
|
prevented.
|
|
|
|
hrtimer_check_target() makes the 'can remote enqueue' decision. As soon as
|
|
hrtimer_check_target() is unconditionally available and
|
|
hrtimer_cpu_base.expires_next is updated by hrtimer_reprogram(),
|
|
hrtimer_force_reprogram() needs to be available unconditionally as well to
|
|
prevent the following scenario with CONFIG_HIGH_RES_TIMERS=n:
|
|
|
|
- the first hrtimer on this CPU is removed and hrtimer_force_reprogram() is
|
|
not executed
|
|
|
|
- CPU goes idle (next timer is calculated and hrtimers are taken into
|
|
account)
|
|
|
|
- a hrtimer is enqueued remote on the idle CPU: hrtimer_check_target()
|
|
compares expiry value and hrtimer_cpu_base.expires_next. The expiry value
|
|
is after expires_next, so the hrtimer is enqueued. This timer will fire
|
|
late, if it expires before the effective first hrtimer on this CPU and
|
|
the comparison was with an outdated expires_next value.
|
|
|
|
To prevent this scenario, make hrtimer_force_reprogram() unconditional
|
|
except the effective reprogramming part, which gets eliminated by the
|
|
compiler in the CONFIG_HIGH_RES_TIMERS=n case.
|
|
|
|
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
|
|
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
|
|
---
|
|
kernel/time/hrtimer.c | 10 ++++------
|
|
1 file changed, 4 insertions(+), 6 deletions(-)
|
|
|
|
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
|
|
index 5fd669dd46be..ce9a3ef7a796 100644
|
|
--- a/kernel/time/hrtimer.c
|
|
+++ b/kernel/time/hrtimer.c
|
|
@@ -523,9 +523,6 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
|
|
{
|
|
ktime_t expires_next;
|
|
|
|
- if (!__hrtimer_hres_active(cpu_base))
|
|
- return;
|
|
-
|
|
expires_next = __hrtimer_get_next_event(cpu_base);
|
|
|
|
if (skip_equal && expires_next == cpu_base->expires_next)
|
|
@@ -534,6 +531,9 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
|
|
cpu_base->expires_next = expires_next;
|
|
|
|
/*
|
|
+ * If hres is not active, hardware does not have to be
|
|
+ * reprogrammed yet.
|
|
+ *
|
|
* If a hang was detected in the last timer interrupt then we
|
|
* leave the hang delay active in the hardware. We want the
|
|
* system to make progress. That also prevents the following
|
|
@@ -547,7 +547,7 @@ hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base, int skip_equal)
|
|
* set. So we'd effectivly block all timers until the T2 event
|
|
* fires.
|
|
*/
|
|
- if (cpu_base->hang_detected)
|
|
+ if (!__hrtimer_hres_active(cpu_base) || cpu_base->hang_detected)
|
|
return;
|
|
|
|
tick_program_event(cpu_base->expires_next, 1);
|
|
@@ -848,7 +848,6 @@ static void __remove_hrtimer(struct hrtimer *timer,
|
|
if (!timerqueue_del(&base->active, &timer->node))
|
|
cpu_base->active_bases &= ~(1 << base->index);
|
|
|
|
-#ifdef CONFIG_HIGH_RES_TIMERS
|
|
/*
|
|
* Note: If reprogram is false we do not update
|
|
* cpu_base->next_timer. This happens when we remove the first
|
|
@@ -859,7 +858,6 @@ static void __remove_hrtimer(struct hrtimer *timer,
|
|
*/
|
|
if (reprogram && timer == cpu_base->next_timer)
|
|
hrtimer_force_reprogram(cpu_base, 1);
|
|
-#endif
|
|
}
|
|
|
|
/*
|
|
--
|
|
2.17.1
|
|
|