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    Subject[PATCH 06/12] irq: implement irq_schedule_poll()
    Date
    Implement and use irq_schedule_poll() to schedule desc->poll_timer
    instead of calling mod_timer directly. irq_schedule_poll() is called
    with desc->lock held and schedules the timer iff necessary - ie. if
    the timer is offline or scheduled to expire later than requested.
    This will be used to share desc->poll_timer.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    kernel/irq/spurious.c | 47 +++++++++++++++++++++++++++++++++++++++++------
    1 files changed, 41 insertions(+), 6 deletions(-)

    diff --git a/kernel/irq/spurious.c b/kernel/irq/spurious.c
    index 0bce0e3..0b8fd0a 100644
    --- a/kernel/irq/spurious.c
    +++ b/kernel/irq/spurious.c
    @@ -23,6 +23,8 @@ enum {

    /* IRQ polling common parameters */
    IRQ_POLL_INTV = HZ / 100, /* from the good ol' 100HZ tick */
    +
    + IRQ_POLL_SLACK = HZ / 1000, /* 10% slack */
    };

    int noirqdebug __read_mostly;
    @@ -43,6 +45,38 @@ static void print_irq_handlers(struct irq_desc *desc)
    }
    }

    +static unsigned long irq_poll_slack(unsigned long intv)
    +{
    + return IRQ_POLL_SLACK;
    +}
    +
    +/**
    + * irq_schedule_poll - schedule IRQ poll
    + * @desc: IRQ desc to schedule poll for
    + * @intv: poll interval
    + *
    + * Schedules @desc->poll_timer. If the timer is already scheduled,
    + * it's modified iff jiffies + @intv + slack is before the timer's
    + * expires. poll_timers aren't taken offline behind this function's
    + * back and the users of this function are guaranteed that poll_irq()
    + * will be called at or before jiffies + @intv + slack.
    + *
    + * CONTEXT:
    + * desc->lock
    + */
    +static void irq_schedule_poll(struct irq_desc *desc, unsigned long intv)
    +{
    + unsigned long expires = jiffies + intv;
    + int slack = irq_poll_slack(intv);
    +
    + if (timer_pending(&desc->poll_timer) &&
    + time_before_eq(desc->poll_timer.expires, expires + slack))
    + return;
    +
    + set_timer_slack(&desc->poll_timer, slack);
    + mod_timer(&desc->poll_timer, expires);
    +}
    +
    /*
    * Recovery handler for misrouted interrupts.
    */
    @@ -207,7 +241,9 @@ void __note_interrupt(unsigned int irq, struct irq_desc *desc,
    desc->depth++;
    desc->chip->disable(irq);

    - mod_timer(&desc->poll_timer, jiffies + IRQ_POLL_INTV);
    + raw_spin_lock(&desc->lock);
    + irq_schedule_poll(desc, IRQ_POLL_INTV);
    + raw_spin_unlock(&desc->lock);
    }
    desc->irqs_unhandled = 0;
    }
    @@ -221,9 +257,8 @@ void poll_irq(unsigned long arg)

    raw_spin_lock_irq(&desc->lock);
    try_one_irq(desc->irq, desc);
    + irq_schedule_poll(desc, IRQ_POLL_INTV);
    raw_spin_unlock_irq(&desc->lock);
    -
    - mod_timer(&desc->poll_timer, jiffies + IRQ_POLL_INTV);
    }

    void irq_poll_action_added(struct irq_desc *desc, struct irqaction *action)
    @@ -238,10 +273,10 @@ void irq_poll_action_added(struct irq_desc *desc, struct irqaction *action)
    __enable_irq(desc, desc->irq, false);
    }

    - raw_spin_unlock_irqrestore(&desc->lock, flags);
    -
    if ((action->flags & IRQF_SHARED) && irqfixup >= IRQFIXUP_POLL)
    - mod_timer(&desc->poll_timer, jiffies + IRQ_POLL_INTV);
    + irq_schedule_poll(desc, IRQ_POLL_INTV);
    +
    + raw_spin_unlock_irqrestore(&desc->lock, flags);
    }

    void irq_poll_action_removed(struct irq_desc *desc, struct irqaction *action)
    --
    1.6.4.2


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