127 lines
3.6 KiB
Diff
127 lines
3.6 KiB
Diff
From 414e79a775070c557fd7de089d2f4a2e41da15ea 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 126/287] 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/timer.c | 35 ++++++++++++++++++++++++++++++++---
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2 files changed, 33 insertions(+), 4 deletions(-)
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diff --git a/include/linux/timer.h b/include/linux/timer.h
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index 6abd913..b703477 100644
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--- a/include/linux/timer.h
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+++ b/include/linux/timer.h
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@@ -276,7 +276,7 @@ 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/timer.c b/kernel/timer.c
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index 9c3c62b..e4b2373 100644
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--- a/kernel/timer.c
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+++ b/kernel/timer.c
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@@ -75,6 +75,7 @@ struct tvec_root {
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struct tvec_base {
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spinlock_t lock;
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struct timer_list *running_timer;
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+ wait_queue_head_t wait_for_running_timer;
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unsigned long timer_jiffies;
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unsigned long next_timer;
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struct tvec_root tv1;
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@@ -679,12 +680,15 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
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debug_activate(timer, expires);
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+ preempt_disable_rt();
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cpu = smp_processor_id();
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#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
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if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
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cpu = get_nohz_timer_target();
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#endif
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+ preempt_enable_rt();
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+
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new_base = per_cpu(tvec_bases, cpu);
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if (base != new_base) {
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@@ -885,6 +889,29 @@ 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 tvec_base *base = timer->base;
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+
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+ if (base->running_timer == timer)
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+ wait_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) wake_up(&(b)->wait_for_tunning_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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@@ -953,7 +980,7 @@ out:
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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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@@ -1013,7 +1040,7 @@ 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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@@ -1124,10 +1151,11 @@ static inline void __run_timers(struct tvec_base *base)
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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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spin_lock_irq(&base->lock);
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}
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}
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- base->running_timer = NULL;
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+ wake_up(&base->wait_for_running_timer);
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spin_unlock_irq(&base->lock);
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}
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@@ -1634,6 +1662,7 @@ static int __cpuinit init_timers_cpu(int cpu)
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}
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spin_lock_init(&base->lock);
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+ init_waitqueue_head(&base->wait_for_running_timer);
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for (j = 0; j < TVN_SIZE; j++) {
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INIT_LIST_HEAD(base->tv5.vec + j);
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