148 lines
4.6 KiB
Diff
148 lines
4.6 KiB
Diff
From 68c147023af2485ad55e27ce69ebe33d126941b8 Mon Sep 17 00:00:00 2001
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 28 Jan 2015 14:10:02 +0100
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Subject: [PATCH] Revert "timers: do not raise softirq unconditionally"
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.0/patches-4.0.4-rt1.tar.xz
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The patch I revert here triggers the HRtimer switch from hardirq instead
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of from softirq. As a result we get a periodic interrupt before the
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switch is complete (that is a hrtimer has been programmed) and so the
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tick still programms periodic mode. Since the timer has been shutdown,
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dev->next_event is set to max and the next increment makes it negative.
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And now we wait…
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/hrtimer.h | 3 ++-
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kernel/time/hrtimer.c | 31 ++++++++++++++++++++++++-------
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kernel/time/timer.c | 46 ++--------------------------------------------
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3 files changed, 28 insertions(+), 52 deletions(-)
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--- a/include/linux/hrtimer.h
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+++ b/include/linux/hrtimer.h
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@@ -457,8 +457,9 @@ extern int schedule_hrtimeout_range_cloc
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unsigned long delta, const enum hrtimer_mode mode, int clock);
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extern int schedule_hrtimeout(ktime_t *expires, const enum hrtimer_mode mode);
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-/* Called from the periodic timer tick */
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+/* Soft interrupt function to run the hrtimer queues: */
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extern void hrtimer_run_queues(void);
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+extern void hrtimer_run_pending(void);
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/* Bootup initialization: */
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extern void __init hrtimers_init(void);
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--- a/kernel/time/hrtimer.c
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+++ b/kernel/time/hrtimer.c
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@@ -1652,6 +1652,30 @@ static void run_hrtimer_softirq(struct s
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}
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/*
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+ * Called from timer softirq every jiffy, expire hrtimers:
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+ *
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+ * For HRT its the fall back code to run the softirq in the timer
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+ * softirq context in case the hrtimer initialization failed or has
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+ * not been done yet.
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+ */
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+void hrtimer_run_pending(void)
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+{
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+ if (hrtimer_hres_active())
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+ return;
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+
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+ /*
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+ * This _is_ ugly: We have to check in the softirq context,
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+ * whether we can switch to highres and / or nohz mode. The
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+ * clocksource switch happens in the timer interrupt with
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+ * xtime_lock held. Notification from there only sets the
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+ * check bit in the tick_oneshot code, otherwise we might
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+ * deadlock vs. xtime_lock.
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+ */
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+ if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
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+ hrtimer_switch_to_hres();
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+}
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+
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+/*
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* Called from hardirq context every jiffy
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*/
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void hrtimer_run_queues(void)
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@@ -1664,13 +1688,6 @@ void hrtimer_run_queues(void)
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if (hrtimer_hres_active())
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return;
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- /*
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- * Check whether we can switch to highres mode.
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- */
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- if (tick_check_oneshot_change(!hrtimer_is_hres_enabled())
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- && hrtimer_switch_to_hres())
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- return;
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-
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for (index = 0; index < HRTIMER_MAX_CLOCK_BASES; index++) {
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base = &cpu_base->clock_base[index];
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if (!timerqueue_getnext(&base->active))
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--- a/kernel/time/timer.c
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+++ b/kernel/time/timer.c
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@@ -1463,6 +1463,8 @@ static void run_timer_softirq(struct sof
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{
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struct tvec_base *base = __this_cpu_read(tvec_bases);
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+ hrtimer_run_pending();
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+
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if (time_after_eq(jiffies, base->timer_jiffies))
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__run_timers(base);
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}
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@@ -1472,52 +1474,8 @@ static void run_timer_softirq(struct sof
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*/
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void run_local_timers(void)
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{
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- struct tvec_base *base = __this_cpu_read(tvec_bases);
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-
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hrtimer_run_queues();
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- /*
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- * We can access this lockless as we are in the timer
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- * interrupt. If there are no timers queued, nothing to do in
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- * the timer softirq.
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- */
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-#ifdef CONFIG_PREEMPT_RT_FULL
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-
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-#ifndef CONFIG_SMP
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- /*
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- * The spin_do_trylock() later may fail as the lock may be hold before
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- * the interrupt arrived. The spin-lock debugging code will raise a
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- * warning if the try_lock fails on UP. Since this is only an
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- * optimization for the FULL_NO_HZ case (not to run the timer softirq on
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- * an nohz_full CPU) we don't really care and shedule the softirq.
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- */
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raise_softirq(TIMER_SOFTIRQ);
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- return;
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-#endif
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-
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- /* On RT, irq work runs from softirq */
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- if (irq_work_needs_cpu()) {
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- raise_softirq(TIMER_SOFTIRQ);
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- return;
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- }
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-
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- if (!spin_do_trylock(&base->lock)) {
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- raise_softirq(TIMER_SOFTIRQ);
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- return;
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- }
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-#endif
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-
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- if (!base->active_timers)
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- goto out;
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-
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- /* Check whether the next pending timer has expired */
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- if (time_before_eq(base->next_timer, jiffies))
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- raise_softirq(TIMER_SOFTIRQ);
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-out:
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-#ifdef CONFIG_PREEMPT_RT_FULL
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- rt_spin_unlock_after_trylock_in_irq(&base->lock);
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-#endif
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- /* The ; ensures that gcc won't complain in the !RT case */
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- ;
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}
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#ifdef __ARCH_WANT_SYS_ALARM
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