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Commit 301a5cba authored by Tang Chen's avatar Tang Chen Committed by Ingo Molnar
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sched: Update sched_domains_numa_masks[][] when new cpus are onlined 



Once array sched_domains_numa_masks[] []is defined, it is never updated.

When a new cpu on a new node is onlined, the coincident member in
sched_domains_numa_masks[][] is not initialized, and all the masks are 0.
As a result, the build_overlap_sched_groups() will initialize a NULL
sched_group for the new cpu on the new node, which will lead to kernel panic:

[ 3189.403280] Call Trace:
[ 3189.403286]  [<ffffffff8106c36f>] warn_slowpath_common+0x7f/0xc0
[ 3189.403289]  [<ffffffff8106c3ca>] warn_slowpath_null+0x1a/0x20
[ 3189.403292]  [<ffffffff810b1d57>] build_sched_domains+0x467/0x470
[ 3189.403296]  [<ffffffff810b2067>] partition_sched_domains+0x307/0x510
[ 3189.403299]  [<ffffffff810b1ea2>] ? partition_sched_domains+0x142/0x510
[ 3189.403305]  [<ffffffff810fcc93>] cpuset_update_active_cpus+0x83/0x90
[ 3189.403308]  [<ffffffff810b22a8>] cpuset_cpu_active+0x38/0x70
[ 3189.403316]  [<ffffffff81674b87>] notifier_call_chain+0x67/0x150
[ 3189.403320]  [<ffffffff81664647>] ? native_cpu_up+0x18a/0x1b5
[ 3189.403328]  [<ffffffff810a044e>] __raw_notifier_call_chain+0xe/0x10
[ 3189.403333]  [<ffffffff81070470>] __cpu_notify+0x20/0x40
[ 3189.403337]  [<ffffffff8166663e>] _cpu_up+0xe9/0x131
[ 3189.403340]  [<ffffffff81666761>] cpu_up+0xdb/0xee
[ 3189.403348]  [<ffffffff8165667c>] store_online+0x9c/0xd0
[ 3189.403355]  [<ffffffff81437640>] dev_attr_store+0x20/0x30
[ 3189.403361]  [<ffffffff8124aa63>] sysfs_write_file+0xa3/0x100
[ 3189.403368]  [<ffffffff811ccbe0>] vfs_write+0xd0/0x1a0
[ 3189.403371]  [<ffffffff811ccdb4>] sys_write+0x54/0xa0
[ 3189.403375]  [<ffffffff81679c69>] system_call_fastpath+0x16/0x1b
[ 3189.403377] ---[ end trace 1e6cf85d0859c941 ]---
[ 3189.403398] BUG: unable to handle kernel NULL pointer dereference at 0000000000000018

This patch registers a new notifier for cpu hotplug notify chain, and
updates sched_domains_numa_masks every time a new cpu is onlined or offlined.

Signed-off-by: default avatarTang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: default avatarWen Congyang <wency@cn.fujitsu.com>
[ fixed compile warning ]
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1348578751-16904-3-git-send-email-tangchen@cn.fujitsu.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 5f7865f3

kernel/sched/core.c

+56 −0
Original line number Diff line number Diff line
@@ -6190,10 +6190,65 @@ static void sched_init_numa(void) 


	sched_domains_numa_levels = level;

}



static void sched_domains_numa_masks_set(int cpu)

{

	int i, j;

	int node = cpu_to_node(cpu);



	for (i = 0; i < sched_domains_numa_levels; i++) {

		for (j = 0; j < nr_node_ids; j++) {

			if (node_distance(j, node) <= sched_domains_numa_distance[i])

				cpumask_set_cpu(cpu, sched_domains_numa_masks[i][j]);

		}

	}

}



static void sched_domains_numa_masks_clear(int cpu)

{

	int i, j;

	for (i = 0; i < sched_domains_numa_levels; i++) {

		for (j = 0; j < nr_node_ids; j++)

			cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]);

	}

}



/*

 * Update sched_domains_numa_masks[level][node] array when new cpus

 * are onlined.

 */

static int sched_domains_numa_masks_update(struct notifier_block *nfb,

					   unsigned long action,

					   void *hcpu)

{

	int cpu = (long)hcpu;



	switch (action & ~CPU_TASKS_FROZEN) {

	case CPU_ONLINE:

		sched_domains_numa_masks_set(cpu);

		break;



	case CPU_DEAD:

		sched_domains_numa_masks_clear(cpu);

		break;



	default:

		return NOTIFY_DONE;

	}



	return NOTIFY_OK;

}

#else

static inline void sched_init_numa(void)

{

}



static int sched_domains_numa_masks_update(struct notifier_block *nfb,

					   unsigned long action,

					   void *hcpu)

{

	return 0;

}

#endif /* CONFIG_NUMA */



static int __sdt_alloc(const struct cpumask *cpu_map)
@@ -6642,6 +6697,7 @@ void __init sched_init_smp(void) 
	mutex_unlock(&sched_domains_mutex);

	put_online_cpus();



	hotcpu_notifier(sched_domains_numa_masks_update, CPU_PRI_SCHED_ACTIVE);

	hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);

	hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);