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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 <yanmin_zhang@linux.intel.com> Tested-by: Vegard Nossum <vegard.nossum@gmail.com> Acked-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Ingo Molnar <mingo@elte.hu> |
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