From cde9070d9970eef1f7ec2360586c802a16230ad8 Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Fri, 10 May 2024 07:43:50 +0000
Subject: [PATCH] rtl88x2CE_WiFi_linux driver
---
kernel/kernel/time/tick-sched.c | 152 ++++++++++++++++++++++++++++++++++++--------------
1 files changed, 108 insertions(+), 44 deletions(-)
diff --git a/kernel/kernel/time/tick-sched.c b/kernel/kernel/time/tick-sched.c
index 07969fa..3b9c648 100644
--- a/kernel/kernel/time/tick-sched.c
+++ b/kernel/kernel/time/tick-sched.c
@@ -54,49 +54,67 @@
*/
static void tick_do_update_jiffies64(ktime_t now)
{
- unsigned long ticks = 0;
+ unsigned long ticks = 1;
ktime_t delta;
/*
- * Do a quick check without holding jiffies_lock:
- * The READ_ONCE() pairs with two updates done later in this function.
+ * Do a quick check without holding jiffies_lock. The READ_ONCE()
+ * pairs with the update done later in this function.
+ *
+ * This is also an intentional data race which is even safe on
+ * 32bit in theory. If there is a concurrent update then the check
+ * might give a random answer. It does not matter because if it
+ * returns then the concurrent update is already taking care, if it
+ * falls through then it will pointlessly contend on jiffies_lock.
+ *
+ * Though there is one nasty case on 32bit due to store tearing of
+ * the 64bit value. If the first 32bit store makes the quick check
+ * return on all other CPUs and the writing CPU context gets
+ * delayed to complete the second store (scheduled out on virt)
+ * then jiffies can become stale for up to ~2^32 nanoseconds
+ * without noticing. After that point all CPUs will wait for
+ * jiffies lock.
+ *
+ * OTOH, this is not any different than the situation with NOHZ=off
+ * where one CPU is responsible for updating jiffies and
+ * timekeeping. If that CPU goes out for lunch then all other CPUs
+ * will operate on stale jiffies until it decides to come back.
*/
- delta = ktime_sub(now, READ_ONCE(last_jiffies_update));
- if (delta < tick_period)
+ if (ktime_before(now, READ_ONCE(tick_next_period)))
return;
/* Reevaluate with jiffies_lock held */
raw_spin_lock(&jiffies_lock);
- write_seqcount_begin(&jiffies_seq);
-
- delta = ktime_sub(now, last_jiffies_update);
- if (delta >= tick_period) {
-
- delta = ktime_sub(delta, tick_period);
- /* Pairs with the lockless read in this function. */
- WRITE_ONCE(last_jiffies_update,
- ktime_add(last_jiffies_update, tick_period));
-
- /* Slow path for long timeouts */
- if (unlikely(delta >= tick_period)) {
- s64 incr = ktime_to_ns(tick_period);
-
- ticks = ktime_divns(delta, incr);
-
- /* Pairs with the lockless read in this function. */
- WRITE_ONCE(last_jiffies_update,
- ktime_add_ns(last_jiffies_update,
- incr * ticks));
- }
- do_timer(++ticks);
-
- /* Keep the tick_next_period variable up to date */
- tick_next_period = ktime_add(last_jiffies_update, tick_period);
- } else {
- write_seqcount_end(&jiffies_seq);
+ if (ktime_before(now, tick_next_period)) {
raw_spin_unlock(&jiffies_lock);
return;
}
+
+ write_seqcount_begin(&jiffies_seq);
+
+ delta = ktime_sub(now, tick_next_period);
+ if (unlikely(delta >= TICK_NSEC)) {
+ /* Slow path for long idle sleep times */
+ s64 incr = TICK_NSEC;
+
+ ticks += ktime_divns(delta, incr);
+
+ last_jiffies_update = ktime_add_ns(last_jiffies_update,
+ incr * ticks);
+ } else {
+ last_jiffies_update = ktime_add_ns(last_jiffies_update,
+ TICK_NSEC);
+ }
+
+ do_timer(ticks);
+
+ /*
+ * Keep the tick_next_period variable up to date. WRITE_ONCE()
+ * pairs with the READ_ONCE() in the lockless quick check above.
+ */
+ WRITE_ONCE(tick_next_period,
+ ktime_add_ns(last_jiffies_update, TICK_NSEC));
+
write_seqcount_end(&jiffies_seq);
raw_spin_unlock(&jiffies_lock);
update_wall_time();
@@ -112,13 +130,26 @@
raw_spin_lock(&jiffies_lock);
write_seqcount_begin(&jiffies_seq);
/* Did we start the jiffies update yet ? */
- if (last_jiffies_update == 0)
+ if (last_jiffies_update == 0) {
+ u32 rem;
+
+ /*
+ * Ensure that the tick is aligned to a multiple of
+ * TICK_NSEC.
+ */
+ div_u64_rem(tick_next_period, TICK_NSEC, &rem);
+ if (rem)
+ tick_next_period += TICK_NSEC - rem;
+
last_jiffies_update = tick_next_period;
+ }
period = last_jiffies_update;
write_seqcount_end(&jiffies_seq);
raw_spin_unlock(&jiffies_lock);
return period;
}
+
+#define MAX_STALLED_JIFFIES 5
static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
{
@@ -147,6 +178,21 @@
if (tick_do_timer_cpu == cpu) {
tick_do_update_jiffies64(now);
trace_android_vh_jiffies_update(NULL);
+ }
+
+ /*
+ * 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)
@@ -213,6 +259,11 @@
if (val & TICK_DEP_MASK_RCU) {
trace_tick_stop(0, TICK_DEP_MASK_RCU);
+ return true;
+ }
+
+ if (val & TICK_DEP_MASK_RCU_EXP) {
+ trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP);
return true;
}
@@ -429,7 +480,7 @@
tick_nohz_full_running = true;
}
-static int tick_nohz_cpu_down(unsigned int cpu)
+bool tick_nohz_cpu_hotpluggable(unsigned int cpu)
{
/*
* The tick_do_timer_cpu CPU handles housekeeping duty (unbound
@@ -437,8 +488,13 @@
* CPUs. It must remain online when nohz full is enabled.
*/
if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
- return -EBUSY;
- return 0;
+ return false;
+ return true;
+}
+
+static int tick_nohz_cpu_down(unsigned int cpu)
+{
+ return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY;
}
void __init tick_nohz_init(void)
@@ -663,7 +719,7 @@
hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
/* Forward the time to expire in the future */
- hrtimer_forward(&ts->sched_timer, now, tick_period);
+ hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
hrtimer_start_expires(&ts->sched_timer,
@@ -831,6 +887,8 @@
if (unlikely(expires == KTIME_MAX)) {
if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
hrtimer_cancel(&ts->sched_timer);
+ else
+ tick_program_event(KTIME_MAX, 1);
return;
}
@@ -1223,11 +1281,17 @@
tick_sched_do_timer(ts, now);
tick_sched_handle(ts, regs);
- /* No need to reprogram if we are running tickless */
- if (unlikely(ts->tick_stopped))
+ if (unlikely(ts->tick_stopped)) {
+ /*
+ * The clockevent device is not reprogrammed, so change the
+ * clock event device to ONESHOT_STOPPED to avoid spurious
+ * interrupts on devices which might not be truly one shot.
+ */
+ tick_program_event(KTIME_MAX, 1);
return;
+ }
- hrtimer_forward(&ts->sched_timer, now, tick_period);
+ hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
}
@@ -1264,7 +1328,7 @@
next = tick_init_jiffy_update();
hrtimer_set_expires(&ts->sched_timer, next);
- hrtimer_forward_now(&ts->sched_timer, tick_period);
+ hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
}
@@ -1330,7 +1394,7 @@
if (unlikely(ts->tick_stopped))
return HRTIMER_NORESTART;
- hrtimer_forward(timer, now, tick_period);
+ hrtimer_forward(timer, now, TICK_NSEC);
return HRTIMER_RESTART;
}
@@ -1364,13 +1428,13 @@
/* Offset the tick to avert jiffies_lock contention. */
if (sched_skew_tick) {
- u64 offset = ktime_to_ns(tick_period) >> 1;
+ u64 offset = TICK_NSEC >> 1;
do_div(offset, num_possible_cpus());
offset *= smp_processor_id();
hrtimer_add_expires_ns(&ts->sched_timer, offset);
}
- hrtimer_forward(&ts->sched_timer, now, tick_period);
+ hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
}
--
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