Re: [PATCH] serialize suspend-resume process

[BVK Chaitanya <bayapuneni_chaitanya@symantec.com>]

Keir Fraser wrote:
> 
> On 31/7/08 14:04, "BVK Chaitanya" <bayapuneni_chaitanya@symantec.com> 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