lkml.org 
[lkml]   [2011]   [Mar]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC PATCH 1/2] genirq: Add chip hooks for taking CPUs on/off line.
    On 03/19/2011 01:51 PM, Thomas Gleixner wrote:
    > On Fri, 18 Mar 2011, David Daney wrote:
    >> --- a/include/linux/irqdesc.h
    >> +++ b/include/linux/irqdesc.h
    >> @@ -178,6 +178,12 @@ static inline int irq_has_action(unsigned int irq)
    >> return desc->action != NULL;
    >> }
    >>
    >> +/* Test to see if the irq is currently enabled */
    >> +static inline int irq_desc_is_enabled(struct irq_desc *desc)
    >> +{
    >> + return desc->depth == 0;
    >> +}
    >
    > That want's to go into kernel/irq/internal.h

    I think I need to use this in my irq_chip.irq_unmask method.

    Consider this:


    CPU0 CPU1
    handle_level_irq
    lock
    mask
    handle_irq_event
    unlock
    .
    . disable_irq
    .
    lock
    unmask
    unlock


    I need to know in my .unmask method if the interrupt has been disabled.
    If it has, I will not re-enable (unmask)it.

    >
    >> #ifndef CONFIG_GENERIC_HARDIRQS_NO_COMPAT
    >> static inline int irq_balancing_disabled(unsigned int irq)
    >> {
    >> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
    >> index c9c0601..40736f7 100644
    >> --- a/kernel/irq/chip.c
    >> +++ b/kernel/irq/chip.c
    >> @@ -689,3 +689,38 @@ void irq_modify_status(unsigned int irq, unsigned long clr, unsigned long set)
    >>
    >> irq_put_desc_unlock(desc, flags);
    >> }
    >> +
    >> +void irq_cpu_online(unsigned int irq)
    >
    > Odd function name. It does not reflect that this is for per cpu
    > interrupts. So something like irq_xxx_per_cpu_irq(irq)
    > might be a bit more descriptive.

    I am using it for per cpu interrupts, but I didn't want to impose that
    policy on others.



    >
    >> +{
    >
    > So that's called on the cpu which goes online, right?
    >

    Yes.

    > I wonder whether we can add any sanity check to verify this.
    >
    > Though I would not worry too much about it. Calling that from a cpu
    > which is not going offline should have enough nasty side effects that
    > it's noticed during development. :)
    >
    >> + unsigned long flags;
    >> + struct irq_chip *chip;
    >> + struct irq_desc *desc = irq_to_desc(irq);
    >
    > Needs to check !desc

    OK.

    >
    >> + raw_spin_lock_irqsave(&desc->lock, flags);
    >> +
    >> + chip = irq_data_get_irq_chip(&desc->irq_data);
    >> +
    >> + if (chip&& chip->irq_cpu_online)
    >> + chip->irq_cpu_online(&desc->irq_data,
    >> + irq_desc_is_enabled(desc));
    >> +
    >> + raw_spin_unlock_irqrestore(&desc->lock, flags);
    >> +}
    >> +
    >> +void irq_cpu_offline(unsigned int irq)
    >> +{
    >> + unsigned long flags;
    >> + struct irq_chip *chip;
    >> + struct irq_desc *desc = irq_to_desc(irq);
    >
    > See above.
    >
    > Style nit: I prefer ordering:
    >
    > + struct irq_desc *desc = irq_to_desc(irq);
    > + struct irq_chip *chip;
    > + unsigned long flags;
    >
    > For some reason, probably because I'm used to it, that's easier to
    > parse. But don't worry about that, I'll turn it around before sticking
    > it into git. :)
    >
    > Otherwise I'm fine with the approach itself.
    >
    > Though one question remains: should we just iterate over the irq space
    > and call the online/offline callbacks when available instead of having
    > the arch code do the iteration.
    >

    That would be good I think, especially for sparse irqs.

    In the case of the CPU going offline, the .irq_cpu_offline() may need to
    adjust the affinity so that the irq no longer has affinity for the
    off-lined CPU.

    This is something needed even for non-per-cpu interrupts. Also I would
    need a way to call irq_set_affinity() while holding the desc->lock.

    David Daney



    \
     
     \ /
      Last update: 2011-03-21 19:29    [W:0.035 / U:0.188 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site