forked from rrcarlosr/Jetpack
168 lines
4.5 KiB
Diff
168 lines
4.5 KiB
Diff
From 160b8852d4b9b1f26e7341c16490f47ea7a6a180 Mon Sep 17 00:00:00 2001
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From: Ingo Molnar <mingo@elte.hu>
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Date: Fri, 3 Jul 2009 08:29:34 -0500
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Subject: [PATCH 119/352] timers: Prepare for full preemption
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When softirqs can be preempted we need to make sure that cancelling
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the timer from the active thread can not deadlock vs. a running timer
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callback. Add a waitqueue to resolve that.
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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include/linux/timer.h | 2 +-
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kernel/sched/core.c | 9 +++++++--
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kernel/time/timer.c | 44 ++++++++++++++++++++++++++++++++++++++++----
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3 files changed, 48 insertions(+), 7 deletions(-)
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diff --git a/include/linux/timer.h b/include/linux/timer.h
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index ec86e4e..8e5b680 100644
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--- a/include/linux/timer.h
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+++ b/include/linux/timer.h
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@@ -241,7 +241,7 @@ extern void add_timer(struct timer_list *timer);
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extern int try_to_del_timer_sync(struct timer_list *timer);
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-#ifdef CONFIG_SMP
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+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
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extern int del_timer_sync(struct timer_list *timer);
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#else
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# define del_timer_sync(t) del_timer(t)
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diff --git a/kernel/sched/core.c b/kernel/sched/core.c
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index e0b1697..d8fffe3 100644
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--- a/kernel/sched/core.c
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+++ b/kernel/sched/core.c
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@@ -540,11 +540,14 @@ void resched_cpu(int cpu)
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*/
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int get_nohz_timer_target(void)
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{
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- int i, cpu = smp_processor_id();
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+ int i, cpu;
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struct sched_domain *sd;
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+ preempt_disable_rt();
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+ cpu = smp_processor_id();
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+
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if (!idle_cpu(cpu) && is_housekeeping_cpu(cpu))
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- return cpu;
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+ goto preempt_en_rt;
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rcu_read_lock();
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for_each_domain(cpu, sd) {
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@@ -563,6 +566,8 @@ int get_nohz_timer_target(void)
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cpu = housekeeping_any_cpu();
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unlock:
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rcu_read_unlock();
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+preempt_en_rt:
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+ preempt_enable_rt();
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return cpu;
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}
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/*
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diff --git a/kernel/time/timer.c b/kernel/time/timer.c
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index f14e352..a0cb1a2 100644
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--- a/kernel/time/timer.c
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+++ b/kernel/time/timer.c
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@@ -195,6 +195,9 @@ EXPORT_SYMBOL(jiffies_64);
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struct timer_base {
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raw_spinlock_t lock;
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struct timer_list *running_timer;
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ struct swait_queue_head wait_for_running_timer;
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+#endif
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unsigned long clk;
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unsigned long next_expiry;
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unsigned int cpu;
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@@ -1168,6 +1171,33 @@ void add_timer_on(struct timer_list *timer, int cpu)
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}
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EXPORT_SYMBOL_GPL(add_timer_on);
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+/*
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+ * Wait for a running timer
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+ */
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+static void wait_for_running_timer(struct timer_list *timer)
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+{
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+ struct timer_base *base;
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+ u32 tf = timer->flags;
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+
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+ if (tf & TIMER_MIGRATING)
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+ return;
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+
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+ base = get_timer_base(tf);
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+ swait_event(base->wait_for_running_timer,
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+ base->running_timer != timer);
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+}
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+
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+# define wakeup_timer_waiters(b) swake_up_all(&(b)->wait_for_running_timer)
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+#else
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+static inline void wait_for_running_timer(struct timer_list *timer)
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+{
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+ cpu_relax();
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+}
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+
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+# define wakeup_timer_waiters(b) do { } while (0)
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+#endif
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+
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/**
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* del_timer - deactive a timer.
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* @timer: the timer to be deactivated
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@@ -1225,7 +1255,7 @@ int try_to_del_timer_sync(struct timer_list *timer)
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}
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EXPORT_SYMBOL(try_to_del_timer_sync);
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-#ifdef CONFIG_SMP
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+#if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RT_FULL)
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/**
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* del_timer_sync - deactivate a timer and wait for the handler to finish.
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* @timer: the timer to be deactivated
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@@ -1285,7 +1315,7 @@ int del_timer_sync(struct timer_list *timer)
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int ret = try_to_del_timer_sync(timer);
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if (ret >= 0)
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return ret;
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- cpu_relax();
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+ wait_for_running_timer(timer);
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}
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}
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EXPORT_SYMBOL(del_timer_sync);
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@@ -1350,13 +1380,16 @@ static void expire_timers(struct timer_base *base, struct hlist_head *head)
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fn = timer->function;
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data = timer->data;
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- if (timer->flags & TIMER_IRQSAFE) {
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+ if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL) &&
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+ timer->flags & TIMER_IRQSAFE) {
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raw_spin_unlock(&base->lock);
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call_timer_fn(timer, fn, data);
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+ base->running_timer = NULL;
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raw_spin_lock(&base->lock);
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} else {
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raw_spin_unlock_irq(&base->lock);
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call_timer_fn(timer, fn, data);
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+ base->running_timer = NULL;
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raw_spin_lock_irq(&base->lock);
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}
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}
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@@ -1673,8 +1706,8 @@ static inline void __run_timers(struct timer_base *base)
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while (levels--)
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expire_timers(base, heads + levels);
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}
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- base->running_timer = NULL;
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raw_spin_unlock_irq(&base->lock);
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+ wakeup_timer_waiters(base);
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}
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/*
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@@ -1917,6 +1950,9 @@ static void __init init_timer_cpu(int cpu)
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base->cpu = cpu;
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raw_spin_lock_init(&base->lock);
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base->clk = jiffies;
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+#ifdef CONFIG_PREEMPT_RT_FULL
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+ init_swait_queue_head(&base->wait_for_running_timer);
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+#endif
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}
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}
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--
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2.7.4
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