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Commit a4c4af7c authored by Heiko Carstens's avatar Heiko Carstens Committed by Linus Torvalds
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[PATCH] cpu hoptlug: avoid usage of smp_processor_id() in preemptible code 



Replace smp_processor_id() with any_online_cpu(cpu_online_map) in order to
avoid lots of "BUG: using smp_processor_id() in preemptible [00000001]
code:..." messages in case taking a cpu online fails.

All the traces start at the last notifier_call_chain(...) in kernel/cpu.c.
Since we hold the cpu_control semaphore it shouldn't be any problem to access
cpu_online_map.

The reason why cpu_up failed is simply that the cpu that was supposed to be
taken online wasn't even there.  That is because on s390 we never know when a
new cpu comes and therefore cpu_possible_map consists of only ones and doesn't
reflect reality.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent cc658cfe

kernel/sched.c

+2 −1
Original line number Diff line number Diff line
@@ -4680,7 +4680,8 @@ static int migration_call(struct notifier_block *nfb, unsigned long action, 
#ifdef CONFIG_HOTPLUG_CPU

	case CPU_UP_CANCELED:

		/* Unbind it from offline cpu so it can run.  Fall thru. */

		kthread_bind(cpu_rq(cpu)->migration_thread,smp_processor_id());

		kthread_bind(cpu_rq(cpu)->migration_thread,

			     any_online_cpu(cpu_online_map));

		kthread_stop(cpu_rq(cpu)->migration_thread);

		cpu_rq(cpu)->migration_thread = NULL;

		break;

kernel/softirq.c

+2 −1
Original line number Diff line number Diff line
@@ -470,7 +470,8 @@ static int __devinit cpu_callback(struct notifier_block *nfb, 
#ifdef CONFIG_HOTPLUG_CPU

	case CPU_UP_CANCELED:

		/* Unbind so it can run.  Fall thru. */

		kthread_bind(per_cpu(ksoftirqd, hotcpu), smp_processor_id());

		kthread_bind(per_cpu(ksoftirqd, hotcpu),

			     any_online_cpu(cpu_online_map));

	case CPU_DEAD:

		p = per_cpu(ksoftirqd, hotcpu);

		per_cpu(ksoftirqd, hotcpu) = NULL;

kernel/softlockup.c

+2 −1
Original line number Diff line number Diff line
@@ -123,7 +123,8 @@ cpu_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) 
#ifdef CONFIG_HOTPLUG_CPU

	case CPU_UP_CANCELED:

		/* Unbind so it can run.  Fall thru. */

		kthread_bind(per_cpu(watchdog_task, hotcpu), smp_processor_id());

		kthread_bind(per_cpu(watchdog_task, hotcpu),

			     any_online_cpu(cpu_online_map));

	case CPU_DEAD:

		p = per_cpu(watchdog_task, hotcpu);

		per_cpu(watchdog_task, hotcpu) = NULL;

kernel/workqueue.c

+1 −1
Original line number Diff line number Diff line
@@ -524,7 +524,7 @@ static int __devinit workqueue_cpu_callback(struct notifier_block *nfb, 
		list_for_each_entry(wq, &workqueues, list) {

			/* Unbind so it can run. */

			kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,

				     smp_processor_id());

				     any_online_cpu(cpu_online_map));

			cleanup_workqueue_thread(wq, hotcpu);

		}

		break;