linux-kernel - [PATCH 4/4] drivers/xen/xenbus/xenbus_client.c: Improve the failure processing for __xenbus_switch

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Message-ID: <5415737D.2030209@gmail.com>
Date:	Sun, 14 Sep 2014 18:52:45 +0800
From:	Chen Gang <gang.chen.5i5j@...il.com>
To:	konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
	David Vrabel <david.vrabel@...rix.com>,
	stefano.stabellini@...citrix.com, mukesh.rathor@...cle.com
CC:	xen-devel@...ts.xenproject.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 4/4] drivers/xen/xenbus/xenbus_client.c: Improve the failure
 processing for __xenbus_switch_state()

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@...il.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

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