Change loops controlled by 'for (i = 0; i < NR_CPUS; i++)' to use 'for_each_possible_cpu(i)' when there's a _remote possibility_ of dereferencing a non-allocated per_cpu variable involved. All files except mm/vmstat.c are x86 arch. Based on 2.6.24-rc3-mm1 . Thanks to pageexec@freemail.hu for pointing this out. Signed-off-by: Mike Travis --- arch/x86/kernel/smp_32.c | 4 ++-- arch/x86/kernel/smpboot_32.c | 4 ++-- arch/x86/xen/smp.c | 4 ++-- mm/vmstat.c | 4 ++-- 4 files changed, 8 insertions(+), 8 deletions(-) --- a/arch/x86/kernel/smp_32.c +++ b/arch/x86/kernel/smp_32.c @@ -223,7 +223,7 @@ void send_IPI_mask_sequence(cpumask_t ma */ local_irq_save(flags); - for (query_cpu = 0; query_cpu < NR_CPUS; ++query_cpu) { + for_each_possible_cpu(query_cpu) { if (cpu_isset(query_cpu, mask)) { __send_IPI_dest_field(cpu_to_logical_apicid(query_cpu), vector); @@ -675,7 +675,7 @@ static int convert_apicid_to_cpu(int api { int i; - for (i = 0; i < NR_CPUS; i++) { + for_each_possible_cpu(i) { if (per_cpu(x86_cpu_to_apicid, i) == apic_id) return i; } --- a/arch/x86/kernel/smpboot_32.c +++ b/arch/x86/kernel/smpboot_32.c @@ -1091,7 +1091,7 @@ static void __init smp_boot_cpus(unsigne * Allow the user to impress friends. */ Dprintk("Before bogomips.\n"); - for (cpu = 0; cpu < NR_CPUS; cpu++) + for_each_possible_cpu(cpu) if (cpu_isset(cpu, cpu_callout_map)) bogosum += cpu_data(cpu).loops_per_jiffy; printk(KERN_INFO @@ -1122,7 +1122,7 @@ static void __init smp_boot_cpus(unsigne * construct cpu_sibling_map, so that we can tell sibling CPUs * efficiently. */ - for (cpu = 0; cpu < NR_CPUS; cpu++) { + for_each_possible_cpu(cpu) { cpus_clear(per_cpu(cpu_sibling_map, cpu)); cpus_clear(per_cpu(cpu_core_map, cpu)); } --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -146,7 +146,7 @@ void __init xen_smp_prepare_boot_cpu(voi old memory can be recycled */ make_lowmem_page_readwrite(&per_cpu__gdt_page); - for (cpu = 0; cpu < NR_CPUS; cpu++) { + for_each_possible_cpu(cpu) { cpus_clear(per_cpu(cpu_sibling_map, cpu)); /* * cpu_core_map lives in a per cpu area that is cleared @@ -163,7 +163,7 @@ void __init xen_smp_prepare_cpus(unsigne { unsigned cpu; - for (cpu = 0; cpu < NR_CPUS; cpu++) { + for_each_possible_cpu(cpu) { cpus_clear(per_cpu(cpu_sibling_map, cpu)); /* * cpu_core_ map will be zeroed when the per --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -27,12 +27,12 @@ static void sum_vm_events(unsigned long memset(ret, 0, NR_VM_EVENT_ITEMS * sizeof(unsigned long)); cpu = first_cpu(*cpumask); - while (cpu < NR_CPUS) { + while (cpu < NR_CPUS && cpu_possible(cpu)) { struct vm_event_state *this = &per_cpu(vm_event_states, cpu); cpu = next_cpu(cpu, *cpumask); - if (cpu < NR_CPUS) + if (cpu < NR_CPUS && cpu_possible(cpu)) prefetch(&per_cpu(vm_event_states, cpu)); -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/