2.6.25-stable review patch. If anyone has any objections, please let us know. ------------------ From: Yanmin Zhang Commit fcb43042ef55d2f46b0efa5d7746967cef38f056 upstream x86: fix cpu hotplug crash Vegard Nossum reported crashes during cpu hotplug tests: http://marc.info/?l=linux-kernel&m=121413950227884&w=4 In function _cpu_up, the panic happens when calling __raw_notifier_call_chain at the second time. Kernel doesn't panic when calling it at the first time. If just say because of nr_cpu_ids, that's not right. By checking the source code, I found that function do_boot_cpu is the culprit. Consider below call chain: _cpu_up=>__cpu_up=>smp_ops.cpu_up=>native_cpu_up=>do_boot_cpu. So do_boot_cpu is called in the end. In do_boot_cpu, if boot_error==true, cpu_clear(cpu, cpu_possible_map) is executed. So later on, when _cpu_up calls __raw_notifier_call_chain at the second time to report CPU_UP_CANCELED, because this cpu is already cleared from cpu_possible_map, get_cpu_sysdev returns NULL. Many resources are related to cpu_possible_map, so it's better not to change it. Below patch against 2.6.26-rc7 fixes it by removing the bit clearing in cpu_possible_map. Signed-off-by: Zhang Yanmin Tested-by: Vegard Nossum Acked-by: Rusty Russell Signed-off-by: Ingo Molnar Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/smpboot_64.c | 1 - 1 file changed, 1 deletion(-) --- a/arch/x86/kernel/smpboot_64.c +++ b/arch/x86/kernel/smpboot_64.c @@ -704,7 +704,6 @@ do_rest: clear_bit(cpu, (unsigned long *)&cpu_initialized); /* was set by cpu_init() */ clear_node_cpumask(cpu); /* was set by numa_add_cpu */ cpu_clear(cpu, cpu_present_map); - cpu_clear(cpu, cpu_possible_map); per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID; return -EIO; } -- -- 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/