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

[Chen Gang <gang.chen.5i5j@gmail.com>]

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@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);
 			goto again;
+		}
 		xenbus_switch_fatal(dev, depth, err, "ending transaction");
 	} else
 		dev->state = state;
 
-	return 0;
+	return err;
 }
 
 /**
-- 
1.9.3