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    Subject[patch 05/14] extend virtual timer interface by mod_virt_timer_periodic
    From: Jan Glauber <jang@linux.vnet.ibm.com>

    In case mod_virt_timer is used to add a non pending timer the timer
    is always added as a one-shot timer. If mod_virt_timer is used for
    periodic timers they may therfore be degraded to one-shot timers.

    Add mod_virt_timer_periodic to the interface to allow safe re-programming
    of the interval value.

    Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
    Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
    ---

    arch/s390/include/asm/timer.h | 1
    arch/s390/kernel/vtime.c | 57 ++++++++++++++++++++++++------------------
    2 files changed, 34 insertions(+), 24 deletions(-)

    Index: quilt-2.6/arch/s390/include/asm/timer.h
    ===================================================================
    --- quilt-2.6.orig/arch/s390/include/asm/timer.h
    +++ quilt-2.6/arch/s390/include/asm/timer.h
    @@ -41,6 +41,7 @@ extern void init_virt_timer(struct vtime
    extern void add_virt_timer(void *new);
    extern void add_virt_timer_periodic(void *new);
    extern int mod_virt_timer(struct vtimer_list *timer, __u64 expires);
    +extern int mod_virt_timer_periodic(struct vtimer_list *timer, __u64 expires);
    extern int del_virt_timer(struct vtimer_list *timer);

    extern void init_cpu_vtimer(void);
    Index: quilt-2.6/arch/s390/kernel/vtime.c
    ===================================================================
    --- quilt-2.6.orig/arch/s390/kernel/vtime.c
    +++ quilt-2.6/arch/s390/kernel/vtime.c
    @@ -425,17 +425,7 @@ void add_virt_timer_periodic(void *new)
    }
    EXPORT_SYMBOL(add_virt_timer_periodic);

    -/*
    - * If we change a pending timer the function must be called on the CPU
    - * where the timer is running on, e.g. by smp_call_function_single()
    - *
    - * The original mod_timer adds the timer if it is not pending. For
    - * compatibility we do the same. The timer will be added on the current
    - * CPU as a oneshot timer.
    - *
    - * returns whether it has modified a pending timer (1) or not (0)
    - */
    -int mod_virt_timer(struct vtimer_list *timer, __u64 expires)
    +int __mod_vtimer(struct vtimer_list *timer, __u64 expires, int periodic)
    {
    struct vtimer_queue *vq;
    unsigned long flags;
    @@ -444,39 +434,35 @@ int mod_virt_timer(struct vtimer_list *t
    BUG_ON(!timer->function);
    BUG_ON(!expires || expires > VTIMER_MAX_SLICE);

    - /*
    - * This is a common optimization triggered by the
    - * networking code - if the timer is re-modified
    - * to be the same thing then just return:
    - */
    if (timer->expires == expires && vtimer_pending(timer))
    return 1;

    cpu = get_cpu();
    vq = &per_cpu(virt_cpu_timer, cpu);

    - /* check if we run on the right CPU */
    - BUG_ON(timer->cpu != cpu);
    -
    /* disable interrupts before test if timer is pending */
    spin_lock_irqsave(&vq->lock, flags);

    /* if timer isn't pending add it on the current CPU */
    if (!vtimer_pending(timer)) {
    spin_unlock_irqrestore(&vq->lock, flags);
    - /* we do not activate an interval timer with mod_virt_timer */
    - timer->interval = 0;
    +
    + if (periodic)
    + timer->interval = expires;
    + else
    + timer->interval = 0;
    timer->expires = expires;
    timer->cpu = cpu;
    internal_add_vtimer(timer);
    return 0;
    }

    + /* check if we run on the right CPU */
    + BUG_ON(timer->cpu != cpu);
    +
    list_del_init(&timer->entry);
    timer->expires = expires;
    -
    - /* also change the interval if we have an interval timer */
    - if (timer->interval)
    + if (periodic)
    timer->interval = expires;

    /* the timer can't expire anymore so we can release the lock */
    @@ -484,9 +470,32 @@ int mod_virt_timer(struct vtimer_list *t
    internal_add_vtimer(timer);
    return 1;
    }
    +
    +/*
    + * If we change a pending timer the function must be called on the CPU
    + * where the timer is running on.
    + *
    + * 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);

    /*
    + * If we change a pending timer the function must be called on the CPU
    + * where the timer is running on.
    + *
    + * 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)
    --
    blue skies,
    Martin.

    "Reality continues to ruin my life." - Calvin.



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