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

[Boris Ostrovsky]

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.5...@gmail.com>
---
  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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