From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Thu, 26 Feb 2009 17:26:38 +0100
Subject: [s390] iucv: failing cpu hot remove for inactive iucv
Message-id: 20090226162638.GA17830@redhat.com
O-Subject: [RHEL5 U4 PATCH 1/1] s390 - iucv: failing cpu hot remove for inactive iucv
Bugzilla: 485412
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>

Description
============

If the iucv module is compiled in/loaded but no user is registered cpu
hot remove doesn't work. Reason for that is that the iucv cpu hotplug
notifier on CPU_DOWN_PREPARE checks if the iucv_buffer_cpumask would
be empty after the corresponding bit would be cleared. However the bit
was never set since iucv wasn't enable. That causes all cpu hot unplug
operations to fail in this scenario.
To fix this use iucv_path_table as an indicator wether iucv is enabled
or not.

Bugzilla
=========

BZ 485412
https://bugzilla.redhat.com/show_bug.cgi?id=

Upstream status of the patch:
=============================

The patch is upstream as of git commit
f1d3e4dca3f8d4f55656477e83d0afe0ea7cbaed,

Test status:
============

The patch has been tested and fixes the problem.
The fix has been verified by the IBM test department.

Please ACK.

With best regards,

	--Hans

diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
index 8b44eb1..b6c76e5 100644
--- a/net/iucv/iucv.c
+++ b/net/iucv/iucv.c
@@ -526,12 +526,12 @@ static int iucv_enable(void)
 	preempt_enable();
 	if (cpus_empty(iucv_buffer_cpumask))
 		/* No cpu could declare an iucv buffer. */
-		goto out_path;
+		goto out;
 	return 0;
 
-out_path:
-	kfree(iucv_path_table);
 out:
+	kfree(iucv_path_table);
+	iucv_path_table = NULL;
 	return rc;
 }
 
@@ -546,6 +546,7 @@ static void iucv_disable(void)
 {
 	on_each_cpu(iucv_retrieve_cpu, NULL, 0, 1);
 	kfree(iucv_path_table);
+	iucv_path_table = NULL;
 }
 
 #ifdef CONFIG_SMP
@@ -689,9 +690,13 @@ static int __cpuinit iucv_cpu_notify(struct notifier_block *self,
 		break;
 	case CPU_ONLINE:
 	case CPU_DOWN_FAILED:
+		if (!iucv_path_table)
+			break;
 		smp_call_function_on(iucv_declare_cpu, NULL, 0, 1, cpu);
 		break;
 	case CPU_DOWN_PREPARE:
+		if (!iucv_path_table)
+			break;
 		cpumask = iucv_buffer_cpumask;
 		cpu_clear(cpu, cpumask);
 		if (cpus_empty(cpumask))