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Date: Tue, 6 Oct 2009 22:07:53 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: Remy Bohmer <linux@bohmer.net>
cc: LKML <linux-kernel@vger.kernel.org>,
       rt-users <linux-rt-users@vger.kernel.org>
Subject: Re: [ANNOUNCE] 2.6.31.2-rt13
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On Tue, 6 Oct 2009, Thomas Gleixner wrote:

> On Tue, 6 Oct 2009, Remy Bohmer wrote:
> > But I was wondering if you missed this one:
> > http://patchwork.kernel.org/patch/50044/
> 
> Yup, slipped through. Queued for the next release.

Correction. I dropped the patch as it is just a sloppy work around. 
Why creating the thread in the first place ? Real fix below.

Thanks,

	tglx
---
diff --git a/kernel/softirq.c b/kernel/softirq.c
index aae8d45..3526976 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -1161,6 +1161,8 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb,
 			per_cpu(ksoftirqd, hotcpu)[i].tsk = NULL;
 		}
 		for (i = 0; i < NR_SOFTIRQS; i++) {
+			if (!softirq_names[i])
+				continue;
 			p = kthread_create(ksoftirqd,
 					   &per_cpu(ksoftirqd, hotcpu)[i],
 					   "sirq-%s/%d", softirq_names[i],
@@ -1177,8 +1179,11 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb,
 	break;
 	case CPU_ONLINE:
 	case CPU_ONLINE_FROZEN:
-		for (i = 0; i < NR_SOFTIRQS; i++)
-			wake_up_process(per_cpu(ksoftirqd, hotcpu)[i].tsk);
+		for (i = 0; i < NR_SOFTIRQS; i++) {
+			p = per_cpu(ksoftirqd, hotcpu)[i].tsk;
+			if (p)
+				wake_up_process(p);
+		}
 		break;
 #ifdef CONFIG_HOTPLUG_CPU
 	case CPU_UP_CANCELED:
@@ -1192,9 +1197,11 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb,
 		for (i = 0; i < NR_SOFTIRQS; i++) {
 			param.sched_priority = MAX_RT_PRIO-1;
 			p = per_cpu(ksoftirqd, hotcpu)[i].tsk;
-			sched_setscheduler(p, SCHED_FIFO, &param);
-			per_cpu(ksoftirqd, hotcpu)[i].tsk = NULL;
-			kthread_stop(p);
+			if (p) {
+				sched_setscheduler(p, SCHED_FIFO, &param);
+				per_cpu(ksoftirqd, hotcpu)[i].tsk = NULL;
+				kthread_stop(p);
+			}
 		}
 		takeover_tasklets(hotcpu);
 		break;