Commit 301a5cba authored Sep 25, 2012 by Tang Chen Committed by Ingo Molnar Oct 05, 2012

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: Tang Chen <tangchen@cn.fujitsu.com>
Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
[ fixed compile warning ]
Signed-off-by: Peter 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: Ingo 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);

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