vtime.c

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/*
 *    Virtual cpu timer based timer functions.
 *
 *    Copyright IBM Corp. 2004, 2012
 *    Author(s): Jan Glauber <[email protected]>
 */

#include <linux/kernel_stat.h>
#include <linux/notifier.h>
#include <linux/kprobes.h>
#include <linux/export.h>
#include <linux/kernel.h>
#include <linux/timex.h>
#include <linux/types.h>
#include <linux/time.h>
#include <linux/cpu.h>
#include <linux/smp.h>

#include <asm/irq_regs.h>
#include <asm/cputime.h>
#include <asm/vtimer.h>
#include <asm/irq.h>
#include "entry.h"

static void virt_timer_expire(void);

DEFINE_PER_CPU(struct s390_idle_data, s390_idle);

static LIST_HEAD(virt_timer_list);
static DEFINE_SPINLOCK(virt_timer_lock);
static atomic64_t virt_timer_current;
static atomic64_t virt_timer_elapsed;

static inline u64 get_vtimer(void)
{
    u64 timer;

    asm volatile("stpt %0" : "=m" (timer));
    return timer;
}

static inline void set_vtimer(u64 expires)
{
    u64 timer;

    asm volatile(
        "   stpt    %0\n"   /* Store current cpu timer value */
        "   spt %1" /* Set new value imm. afterwards */
        : "=m" (timer) : "m" (expires));
    S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
    S390_lowcore.last_update_timer = expires;
}

static inline int virt_timer_forward(u64 elapsed)
{
    BUG_ON(!irqs_disabled());

    if (list_empty(&virt_timer_list))
        return 0;
    elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
    return elapsed >= atomic64_read(&virt_timer_current);
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
static int do_account_vtime(struct task_struct *tsk, int hardirq_offset)
{
    struct thread_info *ti = task_thread_info(tsk);
    u64 timer, clock, user, system, steal;

    timer = S390_lowcore.last_update_timer;
    clock = S390_lowcore.last_update_clock;
    asm volatile(
        "   stpt    %0\n"   /* Store current cpu timer value */
        "   stck    %1" /* Store current tod clock value */
        : "=m" (S390_lowcore.last_update_timer),
          "=m" (S390_lowcore.last_update_clock));
    S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;
    S390_lowcore.steal_timer += S390_lowcore.last_update_clock - clock;

    user = S390_lowcore.user_timer - ti->user_timer;
    S390_lowcore.steal_timer -= user;
    ti->user_timer = S390_lowcore.user_timer;
    account_user_time(tsk, user, user);

    system = S390_lowcore.system_timer - ti->system_timer;
    S390_lowcore.steal_timer -= system;
    ti->system_timer = S390_lowcore.system_timer;
    account_system_time(tsk, hardirq_offset, system, system);

    steal = S390_lowcore.steal_timer;
    if ((s64) steal > 0) {
        S390_lowcore.steal_timer = 0;
        account_steal_time(steal);
    }

    return virt_timer_forward(user + system);
}

void vtime_task_switch(struct task_struct *prev)
{
    struct thread_info *ti;

    do_account_vtime(prev, 0);
    ti = task_thread_info(prev);
    ti->user_timer = S390_lowcore.user_timer;
    ti->system_timer = S390_lowcore.system_timer;
    ti = task_thread_info(current);
    S390_lowcore.user_timer = ti->user_timer;
    S390_lowcore.system_timer = ti->system_timer;
}

void account_process_tick(struct task_struct *tsk, int user_tick)
{
    if (do_account_vtime(tsk, HARDIRQ_OFFSET))
        virt_timer_expire();
}

/*
 * Update process times based on virtual cpu times stored by entry.S
 * to the lowcore fields user_timer, system_timer & steal_clock.
 */
void vtime_account(struct task_struct *tsk)
{
    struct thread_info *ti = task_thread_info(tsk);
    u64 timer, system;

    timer = S390_lowcore.last_update_timer;
    S390_lowcore.last_update_timer = get_vtimer();
    S390_lowcore.system_timer += timer - S390_lowcore.last_update_timer;

    system = S390_lowcore.system_timer - ti->system_timer;
    S390_lowcore.steal_timer -= system;
    ti->system_timer = S390_lowcore.system_timer;
    account_system_time(tsk, 0, system, system);

    virt_timer_forward(system);
}
EXPORT_SYMBOL_GPL(vtime_account);

void __kprobes vtime_stop_cpu(void)
{
    struct s390_idle_data *idle = &__get_cpu_var(s390_idle);
    unsigned long long idle_time;
    unsigned long psw_mask;

    trace_hardirqs_on();
    /* Don't trace preempt off for idle. */
    stop_critical_timings();

    /* Wait for external, I/O or machine check interrupt. */
    psw_mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_DAT |
        PSW_MASK_IO | PSW_MASK_EXT | PSW_MASK_MCHECK;
    idle->nohz_delay = 0;

    /* Call the assembler magic in entry.S */
    psw_idle(idle, psw_mask);

    /* Reenable preemption tracer. */
    start_critical_timings();

    /* Account time spent with enabled wait psw loaded as idle time. */
    idle->sequence++;
    smp_wmb();
    idle_time = idle->clock_idle_exit - idle->clock_idle_enter;
    idle->clock_idle_enter = idle->clock_idle_exit = 0ULL;
    idle->idle_time += idle_time;
    idle->idle_count++;
    account_idle_time(idle_time);
    smp_wmb();
    idle->sequence++;
}

cputime64_t s390_get_idle_time(int cpu)
{
    struct s390_idle_data *idle = &per_cpu(s390_idle, cpu);
    unsigned long long now, idle_enter, idle_exit;
    unsigned int sequence;

    do {
        now = get_clock();
        sequence = ACCESS_ONCE(idle->sequence);
        idle_enter = ACCESS_ONCE(idle->clock_idle_enter);
        idle_exit = ACCESS_ONCE(idle->clock_idle_exit);
    } while ((sequence & 1) || (idle->sequence != sequence));
    return idle_enter ? ((idle_exit ?: now) - idle_enter) : 0;
}

/*
 * Sorted add to a list. List is linear searched until first bigger
 * element is found.
 */
static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
{
    struct vtimer_list *tmp;

    list_for_each_entry(tmp, head, entry) {
        if (tmp->expires > timer->expires) {
            list_add_tail(&timer->entry, &tmp->entry);
            return;
        }
    }
    list_add_tail(&timer->entry, head);
}

/*
 * Handler for expired virtual CPU timer.
 */
static void virt_timer_expire(void)
{
    struct vtimer_list *timer, *tmp;
    unsigned long elapsed;
    LIST_HEAD(cb_list);

    /* walk timer list, fire all expired timers */
    spin_lock(&virt_timer_lock);
    elapsed = atomic64_read(&virt_timer_elapsed);
    list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
        if (timer->expires < elapsed)
            /* move expired timer to the callback queue */
            list_move_tail(&timer->entry, &cb_list);
        else
            timer->expires -= elapsed;
    }
    if (!list_empty(&virt_timer_list)) {
        timer = list_first_entry(&virt_timer_list,
                     struct vtimer_list, entry);
        atomic64_set(&virt_timer_current, timer->expires);
    }
    atomic64_sub(elapsed, &virt_timer_elapsed);
    spin_unlock(&virt_timer_lock);

    /* Do callbacks and recharge periodic timers */
    list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
        list_del_init(&timer->entry);
        timer->function(timer->data);
        if (timer->interval) {
            /* Recharge interval timer */
            timer->expires = timer->interval +
                atomic64_read(&virt_timer_elapsed);
            spin_lock(&virt_timer_lock);
            list_add_sorted(timer, &virt_timer_list);
            spin_unlock(&virt_timer_lock);
        }
    }
}

void init_virt_timer(struct vtimer_list *timer)
{
    timer->function = NULL;
    INIT_LIST_HEAD(&timer->entry);
}
EXPORT_SYMBOL(init_virt_timer);

static inline int vtimer_pending(struct vtimer_list *timer)
{
    return !list_empty(&timer->entry);
}

static void internal_add_vtimer(struct vtimer_list *timer)
{
    if (list_empty(&virt_timer_list)) {
        /* First timer, just program it. */
        atomic64_set(&virt_timer_current, timer->expires);
        atomic64_set(&virt_timer_elapsed, 0);
        list_add(&timer->entry, &virt_timer_list);
    } else {
        /* Update timer against current base. */
        timer->expires += atomic64_read(&virt_timer_elapsed);
        if (likely((s64) timer->expires <
               (s64) atomic64_read(&virt_timer_current)))
            /* The new timer expires before the current timer. */
            atomic64_set(&virt_timer_current, timer->expires);
        /* Insert new timer into the list. */
        list_add_sorted(timer, &virt_timer_list);
    }
}

static void __add_vtimer(struct vtimer_list *timer, int periodic)
{
    unsigned long flags;

    timer->interval = periodic ? timer->expires : 0;
    spin_lock_irqsave(&virt_timer_lock, flags);
    internal_add_vtimer(timer);
    spin_unlock_irqrestore(&virt_timer_lock, flags);
}

/*
 * add_virt_timer - add an oneshot virtual CPU timer
 */
void add_virt_timer(struct vtimer_list *timer)
{
    __add_vtimer(timer, 0);
}
EXPORT_SYMBOL(add_virt_timer);

/*
 * add_virt_timer_int - add an interval virtual CPU timer
 */
void add_virt_timer_periodic(struct vtimer_list *timer)
{
    __add_vtimer(timer, 1);
}
EXPORT_SYMBOL(add_virt_timer_periodic);

static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
{
    unsigned long flags;
    int rc;

    BUG_ON(!timer->function);

    if (timer->expires == expires && vtimer_pending(timer))
        return 1;
    spin_lock_irqsave(&virt_timer_lock, flags);
    rc = vtimer_pending(timer);
    if (rc)
        list_del_init(&timer->entry);
    timer->interval = periodic ? expires : 0;
    timer->expires = expires;
    internal_add_vtimer(timer);
    spin_unlock_irqrestore(&virt_timer_lock, flags);
    return rc;
}

/*
 * returns whether it has modified a pending timer (1) or not (0)
 */
int mod_virt_timer(struct vtimer_list *timer, u64 expires)
{
    return __mod_vtimer(timer, expires, 0);
}
EXPORT_SYMBOL(mod_virt_timer);

/*
 * returns whether it has modified a pending timer (1) or not (0)
 */
int mod_virt_timer_periodic(struct vtimer_list *timer, u64 expires)
{
    return __mod_vtimer(timer, expires, 1);
}
EXPORT_SYMBOL(mod_virt_timer_periodic);

/*
 * Delete a virtual timer.
 *
 * returns whether the deleted timer was pending (1) or not (0)
 */
int del_virt_timer(struct vtimer_list *timer)
{
    unsigned long flags;

    if (!vtimer_pending(timer))
        return 0;
    spin_lock_irqsave(&virt_timer_lock, flags);
    list_del_init(&timer->entry);
    spin_unlock_irqrestore(&virt_timer_lock, flags);
    return 1;
}
EXPORT_SYMBOL(del_virt_timer);

/*
 * Start the virtual CPU timer on the current CPU.
 */
void __cpuinit init_cpu_vtimer(void)
{
    /* set initial cpu timer */
    set_vtimer(VTIMER_MAX_SLICE);
}

static int __cpuinit s390_nohz_notify(struct notifier_block *self,
                      unsigned long action, void *hcpu)
{
    struct s390_idle_data *idle;
    long cpu = (long) hcpu;

    idle = &per_cpu(s390_idle, cpu);
    switch (action & ~CPU_TASKS_FROZEN) {
    case CPU_DYING:
        idle->nohz_delay = 0;
    default:
        break;
    }
    return NOTIFY_OK;
}

void __init vtime_init(void)
{
    /* Enable cpu timer interrupts on the boot cpu. */
    init_cpu_vtimer();
    cpu_notifier(s390_nohz_notify, 0);
}