Re: [Xen-devel] [PATCH V2 2/2] xenbus: defer xenbus frontend resume if xenstored is not running

[Aurelien Chartier <aurelien.chartier@xxxxxxxxxx>]

On 08/05/13 15:32, Aurelien Chartier wrote:
> If the xenbus frontend is running in a domain running xenstored, the device
> resume is hanging because it is happening before the process resume. This
> patch adds extra logic to the resume code to check if we are the domain
> running xenstored and delay the resume if needed.
>
> Signed-off-by: Aurelien Chartier <aurelien.chartier@xxxxxxxxxx>
>
> Changes in v2:
> - Instead of bypassing the resume, process it in a workqueue
> ---
>  drivers/xen/xenbus/xenbus_probe.h          |    5 ++++
>  drivers/xen/xenbus/xenbus_probe_frontend.c |   34 
> +++++++++++++++++++++++++++-
>  2 files changed, 38 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/xen/xenbus/xenbus_probe.h 
> b/drivers/xen/xenbus/xenbus_probe.h
> index 146f857..46b384c 100644
> --- a/drivers/xen/xenbus/xenbus_probe.h
> +++ b/drivers/xen/xenbus/xenbus_probe.h
> @@ -47,6 +47,11 @@ struct xen_bus_type {
>       struct bus_type bus;
>  };
>  
> +struct xenbus_resume_work {
> +     struct work_struct w;
> +     struct device *dev;
> +};
> +
>  enum xenstore_init {
>       XS_UNKNOWN,
>       XS_PV,
> diff --git a/drivers/xen/xenbus/xenbus_probe_frontend.c 
> b/drivers/xen/xenbus/xenbus_probe_frontend.c
> index 3159a37..83b83d0 100644
> --- a/drivers/xen/xenbus/xenbus_probe_frontend.c
> +++ b/drivers/xen/xenbus/xenbus_probe_frontend.c
> @@ -28,6 +28,7 @@
>  #include "xenbus_comms.h"
>  #include "xenbus_probe.h"
>  
> +static struct workqueue_struct *xenbus_frontend_resume_wq;
>  
>  /* device/<type>/<id> => <type>-<id> */
>  static int frontend_bus_id(char bus_id[XEN_BUS_ID_SIZE], const char 
> *nodename)
> @@ -89,9 +90,38 @@ static void backend_changed(struct xenbus_watch *watch,
>       xenbus_otherend_changed(watch, vec, len, 1);
>  }
>  
> +static void xenbus_frontend_delayed_resume(struct work_struct *w)
> +{
> +     struct xenbus_resume_work *resume_work = (struct xenbus_resume_work *) 
> w;
> +
> +     xenbus_dev_resume(dev);
> +
> +     kfree(w);
> +}
> +
> +static int xenbus_frontend_dev_resume(struct device *dev)
> +{
> +     /* 
> +      * If xenstored is running in that domain, we cannot access the backend
> +      * state at the moment, so we need to defer xenbus_dev_resume
> +      */
> +     if (xen_store_domain == XS_LOCAL) {
> +             struct xenbus_resume_work *work =
> +                     kmalloc(sizeof(struct xenbus_resume), GFP_KERNEL);
> +
> +             INIT_WORK((struct work_struct *) work, 
> xenbus_frontend_delayed_resume);
> +             resume_work->dev = dev;
> +             queue_work(xenbus_frontend_resume_wq, (struct work_struct *) 
> work)
Missing a semicolon here.

I should have read that patch once more, apologies for that.

> +
> +             return 0;
> +     }
> +
> +     return xenbus_dev_resume(dev);
> +}
> +
>  static const struct dev_pm_ops xenbus_pm_ops = {
>       .suspend        = xenbus_dev_suspend,
> -     .resume         = xenbus_dev_resume,
> +     .resume         = xenbus_frontend_dev_resume,
>       .freeze         = xenbus_dev_suspend,
>       .thaw           = xenbus_dev_cancel,
>       .restore        = xenbus_dev_resume,
> @@ -440,6 +470,8 @@ static int __init xenbus_probe_frontend_init(void)
>  
>       register_xenstore_notifier(&xenstore_notifier);
>  
> +     xenbus_frontend_resume_wq = create_workqueue("xenbus_frontend_resume");
> +
>       return 0;
>  }
>  subsys_initcall(xenbus_probe_frontend_init);


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