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Koen Kooi
6203cbca5c
Signed-off-by: Koen Kooi <koen@dominion.thruhere.net> Signed-off-by: Denys Dmytriyenko <denys@ti.com>
126 lines
4.4 KiB
Diff
126 lines
4.4 KiB
Diff
From 532c526ac9349430b41f6a16f32fc808c4270647 Mon Sep 17 00:00:00 2001
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From: John Stultz <johnstul@us.ibm.com>
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Date: Tue, 10 Jul 2012 18:43:25 -0400
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Subject: [PATCH 083/109] hrtimer: Update hrtimer base offsets each
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hrtimer_interrupt
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commit 5baefd6d84163443215f4a99f6a20f054ef11236 upstream.
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The update of the hrtimer base offsets on all cpus cannot be made
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atomically from the timekeeper.lock held and interrupt disabled region
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as smp function calls are not allowed there.
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clock_was_set(), which enforces the update on all cpus, is called
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either from preemptible process context in case of do_settimeofday()
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or from the softirq context when the offset modification happened in
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the timer interrupt itself due to a leap second.
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In both cases there is a race window for an hrtimer interrupt between
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dropping timekeeper lock, enabling interrupts and clock_was_set()
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issuing the updates. Any interrupt which arrives in that window will
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see the new time but operate on stale offsets.
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So we need to make sure that an hrtimer interrupt always sees a
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consistent state of time and offsets.
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ktime_get_update_offsets() allows us to get the current monotonic time
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and update the per cpu hrtimer base offsets from hrtimer_interrupt()
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to capture a consistent state of monotonic time and the offsets. The
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function replaces the existing ktime_get() calls in hrtimer_interrupt().
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The overhead of the new function vs. ktime_get() is minimal as it just
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adds two store operations.
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This ensures that any changes to realtime or boottime offsets are
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noticed and stored into the per-cpu hrtimer base structures, prior to
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any hrtimer expiration and guarantees that timers are not expired early.
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Signed-off-by: John Stultz <johnstul@us.ibm.com>
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Reviewed-by: Ingo Molnar <mingo@kernel.org>
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Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Acked-by: Prarit Bhargava <prarit@redhat.com>
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Link: http://lkml.kernel.org/r/1341960205-56738-8-git-send-email-johnstul@us.ibm.com
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
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---
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kernel/hrtimer.c | 28 ++++++++++++++--------------
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1 files changed, 14 insertions(+), 14 deletions(-)
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diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
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index 8f320af..6db7a5e 100644
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--- a/kernel/hrtimer.c
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+++ b/kernel/hrtimer.c
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@@ -657,6 +657,14 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
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return 0;
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}
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+static inline ktime_t hrtimer_update_base(struct hrtimer_cpu_base *base)
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+{
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+ ktime_t *offs_real = &base->clock_base[HRTIMER_BASE_REALTIME].offset;
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+ ktime_t *offs_boot = &base->clock_base[HRTIMER_BASE_BOOTTIME].offset;
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+
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+ return ktime_get_update_offsets(offs_real, offs_boot);
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+}
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+
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/*
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* Retrigger next event is called after clock was set
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*
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@@ -665,22 +673,12 @@ static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
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static void retrigger_next_event(void *arg)
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{
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struct hrtimer_cpu_base *base = &__get_cpu_var(hrtimer_bases);
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- struct timespec realtime_offset, xtim, wtm, sleep;
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if (!hrtimer_hres_active())
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return;
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- /* Optimized out for !HIGH_RES */
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- get_xtime_and_monotonic_and_sleep_offset(&xtim, &wtm, &sleep);
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- set_normalized_timespec(&realtime_offset, -wtm.tv_sec, -wtm.tv_nsec);
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-
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- /* Adjust CLOCK_REALTIME offset */
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raw_spin_lock(&base->lock);
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- base->clock_base[HRTIMER_BASE_REALTIME].offset =
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- timespec_to_ktime(realtime_offset);
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- base->clock_base[HRTIMER_BASE_BOOTTIME].offset =
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- timespec_to_ktime(sleep);
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-
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+ hrtimer_update_base(base);
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hrtimer_force_reprogram(base, 0);
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raw_spin_unlock(&base->lock);
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}
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@@ -710,7 +708,6 @@ static int hrtimer_switch_to_hres(void)
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base->clock_base[i].resolution = KTIME_HIGH_RES;
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tick_setup_sched_timer();
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-
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/* "Retrigger" the interrupt to get things going */
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retrigger_next_event(NULL);
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local_irq_restore(flags);
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@@ -1264,7 +1261,7 @@ void hrtimer_interrupt(struct clock_event_device *dev)
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dev->next_event.tv64 = KTIME_MAX;
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raw_spin_lock(&cpu_base->lock);
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- entry_time = now = ktime_get();
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+ entry_time = now = hrtimer_update_base(cpu_base);
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retry:
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expires_next.tv64 = KTIME_MAX;
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/*
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@@ -1342,9 +1339,12 @@ retry:
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* We need to prevent that we loop forever in the hrtimer
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* interrupt routine. We give it 3 attempts to avoid
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* overreacting on some spurious event.
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+ *
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+ * Acquire base lock for updating the offsets and retrieving
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+ * the current time.
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*/
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raw_spin_lock(&cpu_base->lock);
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- now = ktime_get();
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+ now = hrtimer_update_base(cpu_base);
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cpu_base->nr_retries++;
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if (++retries < 3)
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goto retry;
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--
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1.7.7.6
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