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![Thomas Gleixner](/assets/img/avatar_default.png)
Remove the pointless filenames in the top level comments. They have no value at all and just occupy space. While at it tidy up some of the comments and remove a stale one. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Nicolas Pitre <nico@linaro.org> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Ingo Molnar <mingo@kernel.org> Acked-by: John Stultz <john.stultz@linaro.org> Acked-by: Corey Minyard <cminyard@mvista.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Kate Stewart <kstewart@linuxfoundation.org> Cc: Philippe Ombredanne <pombredanne@nexb.com> Cc: Peter Anvin <hpa@zytor.com> Cc: Russell King <rmk+kernel@armlinux.org.uk> Cc: Richard Cochran <richardcochran@gmail.com> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: David Riley <davidriley@chromium.org> Cc: Colin Cross <ccross@android.com> Cc: Mark Brown <broonie@kernel.org> Link: https://lkml.kernel.org/r/20181031182252.794898238@linutronix.de
110 lines
3 KiB
C
110 lines
3 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Emulate a local clock event device 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 int bc_shutdown(struct clock_event_device *evt)
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{
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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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return 0;
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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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int bc_moved;
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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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* Since we are in the idle loop at this point and because
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* hrtimer_{start/cancel} functions call into tracing,
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* calls to these functions must be bound within RCU_NONIDLE.
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*/
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RCU_NONIDLE({
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bc_moved = hrtimer_try_to_cancel(&bctimer) >= 0;
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if (bc_moved)
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hrtimer_start(&bctimer, expires,
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HRTIMER_MODE_ABS_PINNED);});
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if (bc_moved) {
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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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.name = "bc_hrtimer",
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.set_state_shutdown = bc_shutdown,
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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_possible_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 (clockevent_state_oneshot(&ce_broadcast_hrtimer))
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if (ce_broadcast_hrtimer.next_event != KTIME_MAX)
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return HRTIMER_RESTART;
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return HRTIMER_NORESTART;
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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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