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Commit e67e02a5 authored Nov 28, 2017 by Michael Bringmann Committed by Michael Ellerman Jan 27, 2018

powerpc/pseries: Fix cpu hotplug crash with memoryless nodes



On powerpc systems with shared configurations of CPUs and memory and
memoryless nodes at boot, an event ordering problem was observed on a
SLES12 build platforms with the hot-add of CPUs to the memoryless
nodes.

* The most common error occurred when the memory SLAB driver attempted
  to reference the memoryless node to which a CPU was being added
  before the kernel had finished initializing all of the data
  structures for the CPU and exited 'device_online' under
  DLPAR/hot-add.

  Normally the memoryless node would be initialized through the call
  path device_online ... arch_update_cpu_topology ... find_cpu_nid ...
  try_online_node. This patch ensures that the powerpc node will be
  initialized as early as possible, even if it was memoryless and
  CPU-less at the point when we are trying to hot-add a new CPU to it.

Signed-off-by: Michael Bringmann <mwb@linux.vnet.ibm.com>
Reviewed-by: Nathan Fontenot <nfont@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

parent ea05ba7c

arch/powerpc/mm/numa.c

+3 −1

Original line number	Original line	Diff line number	Diff line
	@@ -1198,7 +1198,7 @@ static long vphn_get_associativity(unsigned long cpu,
	return rc;		return rc;
	}		}

	static inline int find_and_online_cpu_nid(int cpu)		int find_and_online_cpu_nid(int cpu)
	{		{
	__be32 associativity[VPHN_ASSOC_BUFSIZE] = {0};		__be32 associativity[VPHN_ASSOC_BUFSIZE] = {0};
	int new_nid;		int new_nid;
	@@ -1229,6 +1229,8 @@ static inline int find_and_online_cpu_nid(int cpu)
	#endif		#endif
	}		}

			pr_debug("%s:%d cpu %d nid %d\n", __FUNCTION__, __LINE__,
			cpu, new_nid);
	return new_nid;		return new_nid;
	}		}

arch/powerpc/platforms/pseries/hotplug-cpu.c

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -340,6 +340,8 @@ static void pseries_remove_processor(struct device_node *np)
	cpu_maps_update_done();		cpu_maps_update_done();
	}		}

			extern int find_and_online_cpu_nid(int cpu);

	static int dlpar_online_cpu(struct device_node *dn)		static int dlpar_online_cpu(struct device_node *dn)
	{		{
	int rc = 0;		int rc = 0;
	@@ -364,6 +366,7 @@ static int dlpar_online_cpu(struct device_node *dn)
	!= CPU_STATE_OFFLINE);		!= CPU_STATE_OFFLINE);
	cpu_maps_update_done();		cpu_maps_update_done();
	timed_topology_update(1);		timed_topology_update(1);
			find_and_online_cpu_nid(cpu);
	rc = device_online(get_cpu_device(cpu));		rc = device_online(get_cpu_device(cpu));
	if (rc)		if (rc)
	goto out;		goto out;