Re: [Xen-devel] [PATCH] serialize suspend-resume process

[BVK Chaitanya <bayapuneni_chaitanya@xxxxxxxxxxxx>]

Keir Fraser wrote:
> On 31/7/08 14:04, "BVK Chaitanya" <bayapuneni_chaitanya@xxxxxxxxxxxx> wrote:
>
> > With suspend event channel in place, i see that suspend request doesn't
> > go through the shutdown_handler function when suspend is triggered over
> > event channel.
> Oh, I agree that the shutdown_handler() can be re-entered! But it will *not*
> trigger multiple invocations of xen_suspend() -- note it stores away the
> suspend request by performing xchg(&shutting_down, ...) but it does *not*
> immediately trigger a suspend unless old_state==SHUTDOWN_INVALID (in which
> case there is no active current invocation of xen_suspend()).
In my tree there are two shutdown_handler functions.

    shutdown_handler
    __shutdown_handler

First one is called through xenbus interface and ensures that 
xen_suspend is serialized.  I agree about this.
Second one is called through suspend_int (handler for suspend event 
channel) as below:

    static irqreturn_t suspend_int(int irq, void* dev_id,
                                   struct pt_regs *ptregs)
    {
        shutting_down = SHUTDOWN_SUSPEND;
        schedule_work(&shutdown_work);

        return IRQ_HANDLED;
    }



where shutdown_work & its callback are:



    static DECLARE_WORK(shutdown_work, __shutdown_handler, NULL);

    static void __shutdown_handler(void *unused)
    {
        int err;

        err = kernel_thread((shutting_down == SHUTDOWN_SUSPEND) ?
                            xen_suspend : shutdown_process,
                            NULL, CLONE_FS | CLONE_FILES);

        if (err < 0) {
                printk(KERN_WARNING "Error creating shutdown"
                       " process (%d): "
                       "retrying...\n", -err);
                schedule_delayed_work(&shutdown_work, HZ/2);
        }
    }



This second function creates a thread and calls xen_suspend without 
looking for shutting_down variable's value.
I will check my tree again and will get back to you.


--
bvk-chaitanya



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