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Date: Fri, 24 Oct 2014 17:36:56 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Li, Aubrey" <aubrey.li@...ux.intel.com>
Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>,
"Brown, Len" <len.brown@...el.com>,
"alan@...ux.intel.com" <alan@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
"linux-pm@...r.kernel.org >> Linux PM list"
<linux-pm@...r.kernel.org>
Subject: Re: [RFC/PATCH] PM / Sleep: Timer quiesce in freeze state
On Tue, Oct 21, 2014 at 11:15:10PM +0800, Li, Aubrey wrote:
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -917,6 +917,14 @@ static void local_apic_timer_interrupt(void)
> */
> inc_irq_stat(apic_timer_irqs);
>
> + /*
> + * if timekeeping is suspended, the clock event device will be
> + * suspended as well, so we are not supposed to invoke the event
> + * handler of clock event device.
> + */
> + if (unlikely(timekeeping_suspended))
> + return;
> +
> evt->event_handler(evt);
> }
>
How would this even happen? Didn't we just suspend the lapic?
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 4ca9a33..e58d880 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -28,16 +28,20 @@
> #include <linux/ftrace.h>
> #include <trace/events/power.h>
> #include <linux/compiler.h>
> +#include <linux/stop_machine.h>
> +#include <linux/clockchips.h>
> +#include <linux/hrtimer.h>
>
> #include "power.h"
> +#include "../time/tick-internal.h"
> +#include "../time/timekeeping_internal.h"
>
> const char *pm_labels[] = { "mem", "standby", "freeze", NULL };
> const char *pm_states[PM_SUSPEND_MAX];
>
> static const struct platform_suspend_ops *suspend_ops;
> static const struct platform_freeze_ops *freeze_ops;
> -static DECLARE_WAIT_QUEUE_HEAD(suspend_freeze_wait_head);
> -static bool suspend_freeze_wake;
> +static int suspend_freeze_wake;
>
> void freeze_set_ops(const struct platform_freeze_ops *ops)
> {
> @@ -48,22 +52,179 @@ void freeze_set_ops(const struct platform_freeze_ops *ops)
>
> static void freeze_begin(void)
> {
> - suspend_freeze_wake = false;
> + suspend_freeze_wake = -1;
> }
>
> -static void freeze_enter(void)
> +enum freezer_state {
> + FREEZER_NONE,
> + FREEZER_PICK_TK,
> + FREEZER_SUSPEND_CLKEVT,
> + FREEZER_SUSPEND_TK,
> + FREEZER_IDLE,
> + FREEZER_RESUME_TK,
> + FREEZER_RESUME_CLKEVT,
> + FREEZER_EXIT,
> +};
> +
> +struct freezer_data {
> + int thread_num;
> + atomic_t thread_ack;
> + enum freezer_state state;
> +};
> +
> +static void set_state(struct freezer_data *fd, enum freezer_state state)
> +{
> + /* set ack counter */
> + atomic_set(&fd->thread_ack, fd->thread_num);
> + /* guarantee the write ordering between ack counter and state */
> + smp_wmb();
> + fd->state = state;
> +}
> +
> +static void ack_state(struct freezer_data *fd)
> +{
> + if (atomic_dec_and_test(&fd->thread_ack))
> + set_state(fd, fd->state + 1);
> +}
> +
> +static void freezer_pick_tk(int cpu)
> +{
> + if (tick_do_timer_cpu == TICK_DO_TIMER_NONE) {
> + static DEFINE_SPINLOCK(lock);
> +
> + spin_lock(&lock);
> + if (tick_do_timer_cpu == TICK_DO_TIMER_NONE)
> + tick_do_timer_cpu = cpu;
> + spin_unlock(&lock);
> + }
> +}
> +
> +static void freezer_suspend_clkevt(int cpu)
> +{
> + if (tick_do_timer_cpu == cpu)
> + return;
> +
> + clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
> +}
> +
> +static void freezer_suspend_tk(int cpu)
> {
> + if (tick_do_timer_cpu != cpu)
> + return;
> +
I had a note here that this might be broken for clocksource drivers that
have suspend/resume methods. You seem to have 'lost' that note, is that
because you found it isn't a problem?
> + timekeeping_suspend();
> +
> cpuidle_use_deepest_state(true);
> cpuidle_resume();
> - wait_event(suspend_freeze_wait_head, suspend_freeze_wake);
> +}
> +
> +static void freezer_idle(int cpu)
> +{
> + struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
> + struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
> +
> + stop_critical_timings();
> +
> + while (suspend_freeze_wake == -1) {
> + int next_state;
> +
> + /*
> + * interrupt must be disabled before cpu enters idle
> + */
> + local_irq_disable();
> +
> + next_state = cpuidle_select(drv, dev);
> + if (next_state < 0) {
> + arch_cpu_idle();
> + continue;
> + }
> + /*
> + * cpuidle_enter will return with interrupt enabled
> + */
> + cpuidle_enter(drv, dev, next_state);
> + }
> +
> + if (suspend_freeze_wake == cpu)
> + kick_all_cpus_sync();
> +
So I disabled IRQs here
> + start_critical_timings();
> +}
> +
> +static void freezer_resume_tk(int cpu)
> +{
> + if (tick_do_timer_cpu != cpu)
> + return;
> +
> cpuidle_pause();
> cpuidle_use_deepest_state(false);
> +
Such that they would still be disabled here
> + local_irq_disable();
> + timekeeping_resume();
> + local_irq_enable();
> +}
> +
> +static void freezer_resume_clkevt(int cpu)
> +{
> + if (tick_do_timer_cpu == cpu)
> + return;
> +
> + touch_softlockup_watchdog();
> + clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
And here.
> + local_irq_disable();
> + hrtimers_resume();
> + local_irq_enable();
> +}
> +
> +typedef void (*freezer_fn)(int);
> +
> +static freezer_fn freezer_func[FREEZER_EXIT] = {
> + NULL,
> + freezer_pick_tk,
> + freezer_suspend_clkevt,
> + freezer_suspend_tk,
> + freezer_idle,
> + freezer_resume_tk,
> + freezer_resume_clkevt,
> +};
Because this is a stop_machine callback, which are nominally run with
IRQs disabled.
> +static int freezer_stopper_fn(void *arg)
> +{
> + struct freezer_data *fd = arg;
> + enum freezer_state state = FREEZER_NONE;
> + int cpu = smp_processor_id();
> +
> + do {
> + cpu_relax();
> + if (fd->state != state) {
> + state = fd->state;
> + if (freezer_func[state])
> + (*freezer_func[state])(cpu);
> + ack_state(fd);
> + }
> + } while (fd->state != FREEZER_EXIT);
> + return 0;
> +}
Now I suppose the problem is with cpu_pause() which needs IPIs to
complete? Do we really need cpuidle_pause() there?
cpuidle_uninstall_handlers() seems like a daft thing to call just about
there.
--
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