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	Diff line number	Diff line
		@@ -1198,7 +1198,7 @@ static long vphn_get_associativity(unsigned long cpu,
		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};
		int new_nid;
		@@ -1229,6 +1229,8 @@ static inline int find_and_online_cpu_nid(int cpu)
		#endif
		}

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

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

+3 −0

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

		extern int find_and_online_cpu_nid(int cpu);

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

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