On 11/16/2017 11:28 AM, Michael Bringmann wrote: > 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 <m...@linux.vnet.ibm.com> > --- > Changes in V7: > -- Make function find_cpu_nid() externally visible/usable so that > it may be used from hotplug-cpu.c > --- > arch/powerpc/mm/numa.c | 3 ++- > arch/powerpc/platforms/pseries/hotplug-cpu.c | 3 +++ > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c > index 163f4cc..d6d4f7c 100644 > --- a/arch/powerpc/mm/numa.c > +++ b/arch/powerpc/mm/numa.c > @@ -1310,7 +1310,7 @@ static long vphn_get_associativity(unsigned long cpu, > return rc; > } > > -static inline int find_cpu_nid(int cpu) > +int find_cpu_nid(int cpu) > { > __be32 associativity[VPHN_ASSOC_BUFSIZE] = {0}; > int new_nid; > @@ -1343,6 +1343,7 @@ static inline int find_cpu_nid(int cpu) > #endif > } > > + printk(KERN_INFO "%s:%d cpu %d nid %d\n", __FUNCTION__, __LINE__, cpu, > new_nid);
This seems like a more likely pr_debug statement. > return new_nid; > } > > diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c > b/arch/powerpc/platforms/pseries/hotplug-cpu.c > index a7d14aa7..df8c732 100644 > --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c > +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c > @@ -340,6 +340,8 @@ static void pseries_remove_processor(struct device_node > *np) > cpu_maps_update_done(); > } > > +extern int find_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_cpu_nid(cpu); We don't use the returned node from this call, so I'm not sure why it gets called. Perhaps its the possible call to try_online_node() that may get called in find_cpu_nid(), if so perhpas naming the routine something slightly different would be good, like find_and_online_cpu_nid? -Nathan > rc = device_online(get_cpu_device(cpu)); > if (rc) > goto out; >