From: Christoph Lameter ACPI uses NR_CPUS in various loops and in some it accesses per cpu data of processors that are not present(!) and that will never be present. The pointers to per cpu data are typically not initialized for processors that are not present. So we seem to be reading something here from offset 0 in memory. Make ACPI use nr_cpu_ids instead. That stops at the end of the possible processors. Convert one loop to NR_CPUS to use the cpu_possible map instead. That way ranges of processor that can never be brought online are skipped during the loop. Signed-off-by: Christoph Lameter Cc: Len Brown Signed-off-by: Andrew Morton --- drivers/acpi/processor_core.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff -puN drivers/acpi/processor_core.c~acpi-avoid-references-to-impossible-processors drivers/acpi/processor_core.c --- a/drivers/acpi/processor_core.c~acpi-avoid-references-to-impossible-processors +++ a/drivers/acpi/processor_core.c @@ -494,7 +494,7 @@ static int get_cpu_id(acpi_handle handle if (apic_id == -1) return apic_id; - for (i = 0; i < NR_CPUS; ++i) { + for_each_possible_cpu(i) { if (cpu_physical_id(i) == apic_id) return i; } @@ -632,7 +632,7 @@ static int __cpuinit acpi_processor_star return 0; } - BUG_ON((pr->id >= NR_CPUS) || (pr->id < 0)); + BUG_ON((pr->id >= nr_cpu_ids) || (pr->id < 0)); /* * Buggy BIOS check @@ -771,7 +771,7 @@ static int acpi_processor_remove(struct pr = acpi_driver_data(device); - if (pr->id >= NR_CPUS) { + if (pr->id >= nr_cpu_ids) { kfree(pr); return 0; } @@ -842,7 +842,7 @@ int acpi_processor_device_add(acpi_handl if (!pr) return -ENODEV; - if ((pr->id >= 0) && (pr->id < NR_CPUS)) { + if ((pr->id >= 0) && (pr->id < nr_cpu_ids)) { kobject_uevent(&(*device)->dev.kobj, KOBJ_ONLINE); } return 0; @@ -880,13 +880,13 @@ acpi_processor_hotplug_notify(acpi_handl break; } - if (pr->id >= 0 && (pr->id < NR_CPUS)) { + if (pr->id >= 0 && (pr->id < nr_cpu_ids)) { kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE); break; } result = acpi_processor_start(device); - if ((!result) && ((pr->id >= 0) && (pr->id < NR_CPUS))) { + if ((!result) && ((pr->id >= 0) && (pr->id < nr_cpu_ids))) { kobject_uevent(&device->dev.kobj, KOBJ_ONLINE); } else { printk(KERN_ERR PREFIX "Device [%s] failed to start\n", @@ -909,7 +909,7 @@ acpi_processor_hotplug_notify(acpi_handl return; } - if ((pr->id < NR_CPUS) && (cpu_present(pr->id))) + if ((pr->id < nr_cpu_ids) && (cpu_present(pr->id))) kobject_uevent(&device->dev.kobj, KOBJ_OFFLINE); break; default: _