wait for devices before continuing

PATCH New Rik van Riel 1 participant 1 message Aug 11, 2006 Xen hypervisor interface

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Rik van Riel

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2006-08-11 20:11 UTC #0 lore raw

PATCH 1/1 wait for devices before continuing

This patch fixes the "could not found the root filesystem after the blkfront driver was loaded" race condition, which can occur if blkfront does not get the disk hooked up before mount, or the lvm tools, have already run.

It does this by simply waiting for all xenbus devices (which have drivers loaded) to be attached to the driver before continuing after the module initialization.

I have test booted this a number of times and the bootup race condition appears to be gone.

Signed-off-by Rik van Riel <[email protected]>

Signature · 3 lines

"Debugging is twice as hard as writing the code in the first place.
Therefore, if you write the code as cleverly as possible, you are,
by definition, not smart enough to debug it." - Brian W. Kernighan

drivers/xen/blkfront/blkfront.c renamed from drivers/xen/blkfront/blkfront.c.waitforme +8 -1

@@ -824,10 +824,17 @@ static struct xenbus_driver blkfront = {
 
 static int __init xlblk_init(void)
 {
+	int ret;
+
 	if (!is_running_on_xen())
 		return -ENODEV;
 
-	return xenbus_register_frontend(&blkfront);
+	ret = xenbus_register_frontend(&blkfront);
+	if (ret)
+		return ret;
+
+	xenbus_wait_for_devices();
+	return 0;
 }
 module_init(xlblk_init);

drivers/xen/netfront/netfront.c renamed from drivers/xen/netfront/netfront.c.waitforme +8 -1

@@ -1579,6 +1579,8 @@ static struct notifier_block notifier_in
 
 static int __init netif_init(void)
 {
+	int ret;
+
 	if (!is_running_on_xen())
 		return -ENODEV;

@@ -1589,7 +1591,12 @@ static int __init netif_init(void)
 
 	(void)register_inetaddr_notifier(&notifier_inetdev);
 
-	return xenbus_register_frontend(&netfront);
+	ret = xenbus_register_frontend(&netfront);
+	if (ret)
+		return ret;
+
+	xenbus_wait_for_devices();
+	return 0;
 }
 module_init(netif_init);

drivers/xen/xenbus/xenbus_probe.c renamed from drivers/xen/xenbus/xenbus_probe.c.waitforme +3 -2

@@ -1067,7 +1067,7 @@ static int print_device_status(struct de
  * boot slightly, but of course needs tools or manual intervention to set up
  * those flags correctly.
  */
-static int __init wait_for_devices(void)
+int xenbus_wait_for_devices(void)
 {
 	unsigned long timeout = jiffies + 10*HZ;

@@ -1083,4 +1083,5 @@ static int __init wait_for_devices(void)
 	return 0;
 }
 
-late_initcall(wait_for_devices);
+EXPORT_SYMBOL(xenbus_wait_for_devices);
+late_initcall(xenbus_wait_for_devices);

include/xen/xenbus.h renamed from include/xen/xenbus.h.waitforme +1 -0

@@ -157,6 +157,7 @@ int register_xenbus_watch(struct xenbus_
 void unregister_xenbus_watch(struct xenbus_watch *watch);
 void xs_suspend(void);
 void xs_resume(void);
+int xenbus_wait_for_devices(void);
 
 /* Used by xenbus_dev to borrow kernel's store connection. */
 void *xenbus_dev_request_and_reply(struct xsd_sockmsg *msg);

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