849401b66d
The hrtimer mode of broadcast is supported only when GENERIC_CLOCKEVENTS_BROADCAST and TICK_ONESHOT config options are enabled. Hence compile in the functions for hrtimer mode of broadcast only when these options are selected. Also fix max_delta_ticks value for the pseudo clock device. Reported-by: Fengguang Wu <fengguang.wu@intel.com> Reported-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Link: http://lkml.kernel.org/r/52F719EE.9010304@linux.vnet.ibm.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
106 lines
2.7 KiB
C
106 lines
2.7 KiB
C
/*
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* linux/kernel/time/tick-broadcast-hrtimer.c
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* This file emulates a local clock event device
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* via a pseudo clock device.
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*/
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#include <linux/cpu.h>
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#include <linux/err.h>
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#include <linux/hrtimer.h>
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#include <linux/interrupt.h>
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#include <linux/percpu.h>
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#include <linux/profile.h>
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#include <linux/clockchips.h>
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#include <linux/sched.h>
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#include <linux/smp.h>
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#include <linux/module.h>
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#include "tick-internal.h"
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static struct hrtimer bctimer;
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static void bc_set_mode(enum clock_event_mode mode,
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struct clock_event_device *bc)
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{
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switch (mode) {
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case CLOCK_EVT_MODE_SHUTDOWN:
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/*
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* Note, we cannot cancel the timer here as we might
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* run into the following live lock scenario:
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*
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* cpu 0 cpu1
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* lock(broadcast_lock);
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* hrtimer_interrupt()
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* bc_handler()
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* tick_handle_oneshot_broadcast();
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* lock(broadcast_lock);
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* hrtimer_cancel()
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* wait_for_callback()
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*/
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hrtimer_try_to_cancel(&bctimer);
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break;
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default:
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break;
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}
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}
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/*
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* This is called from the guts of the broadcast code when the cpu
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* which is about to enter idle has the earliest broadcast timer event.
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*/
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static int bc_set_next(ktime_t expires, struct clock_event_device *bc)
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{
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/*
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* We try to cancel the timer first. If the callback is on
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* flight on some other cpu then we let it handle it. If we
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* were able to cancel the timer nothing can rearm it as we
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* own broadcast_lock.
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*
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* However we can also be called from the event handler of
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* ce_broadcast_hrtimer itself when it expires. We cannot
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* restart the timer because we are in the callback, but we
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* can set the expiry time and let the callback return
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* HRTIMER_RESTART.
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*/
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if (hrtimer_try_to_cancel(&bctimer) >= 0) {
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hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED);
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/* Bind the "device" to the cpu */
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bc->bound_on = smp_processor_id();
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} else if (bc->bound_on == smp_processor_id()) {
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hrtimer_set_expires(&bctimer, expires);
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}
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return 0;
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}
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static struct clock_event_device ce_broadcast_hrtimer = {
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.set_mode = bc_set_mode,
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.set_next_ktime = bc_set_next,
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.features = CLOCK_EVT_FEAT_ONESHOT |
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CLOCK_EVT_FEAT_KTIME |
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CLOCK_EVT_FEAT_HRTIMER,
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.rating = 0,
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.bound_on = -1,
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.min_delta_ns = 1,
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.max_delta_ns = KTIME_MAX,
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.min_delta_ticks = 1,
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.max_delta_ticks = ULONG_MAX,
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.mult = 1,
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.shift = 0,
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.cpumask = cpu_all_mask,
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};
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static enum hrtimer_restart bc_handler(struct hrtimer *t)
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{
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ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer);
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if (ce_broadcast_hrtimer.next_event.tv64 == KTIME_MAX)
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return HRTIMER_NORESTART;
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return HRTIMER_RESTART;
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}
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void tick_setup_hrtimer_broadcast(void)
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{
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hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
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bctimer.function = bc_handler;
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clockevents_register_device(&ce_broadcast_hrtimer);
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}
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