Re: [Xen-devel] [PATCH 4/4] drivers/xen/xenbus/xenbus_client.c: Improve the failure processing for __xenbus_switch_state()

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 09/14/2014 06:52 AM, Chen Gang wrote:
> When failure occurs, need return failure code instead of 0, or the upper
> caller will misunderstand.
>
> Also when retry for EAGAIN reason, better to schedule out for a while,
> so can let others have chance to continue their tasks (especially,
> their tasks are related EAGAIN under UP kernel).
>
> Signed-off-by: Chen Gang <gang.chen.5i5j@xxxxxxxxx>
> ---
>   drivers/xen/xenbus/xenbus_client.c | 9 ++++++---
>   1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/xen/xenbus/xenbus_client.c 
> b/drivers/xen/xenbus/xenbus_client.c
> index 620ffd2..fc8699b 100644
> --- a/drivers/xen/xenbus/xenbus_client.c
> +++ b/drivers/xen/xenbus/xenbus_client.c
> @@ -36,6 +36,7 @@
>   #include <linux/spinlock.h>
>   #include <linux/vmalloc.h>
>   #include <linux/export.h>
> +#include <linux/delay.h>
>   #include <asm/xen/hypervisor.h>
>   #include <asm/xen/page.h>
>   #include <xen/interface/xen.h>
> @@ -196,7 +197,7 @@ again:
>         err = xenbus_transaction_start(&xbt);
>         if (err) {
>                 xenbus_switch_fatal(dev, depth, err, "starting transaction");
> -               return 0;
> +               return err;
>         }
>   
>   	err = xenbus_scanf(xbt, dev->nodename, "state", "%d", &current_state);
> @@ -213,13 +214,15 @@ again:
>   abort:
>         err = xenbus_transaction_end(xbt, abort);
>         if (err) {
> -               if (err == -EAGAIN && !abort)
> +               if (err == -EAGAIN && !abort) {
> +                       msleep(20);
I'd suggest you use schedule() here.

-boris

>                         goto again;
> +               }
>                 xenbus_switch_fatal(dev, depth, err, "ending transaction");
>         } else
>                 dev->state = state;
>   
> -	return 0;
> +       return err;
>   }
>   
>   /**

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