KOSAKI Motohiro 7d6b46707f x86, NUMA: Fix fakenuma boot failure ... Currently, numa=fake boot parameter is broken. If it's used, kernel may panic due to devide by zero error depending on CPU configuration Call Trace: [<ffffffff8104ad4c>] find_busiest_group+0x38c/0xd30 [<ffffffff81086aff>] ? local_clock+0x6f/0x80 [<ffffffff81050533>] load_balance+0xa3/0x600 [<ffffffff81050f53>] idle_balance+0xf3/0x180 [<ffffffff81550092>] schedule+0x722/0x7d0 [<ffffffff81550538>] ? wait_for_common+0x128/0x190 [<ffffffff81550a65>] schedule_timeout+0x265/0x320 [<ffffffff81095815>] ? lock_release_holdtime+0x35/0x1a0 [<ffffffff81550538>] ? wait_for_common+0x128/0x190 [<ffffffff8109bb6c>] ? __lock_release+0x9c/0x1d0 [<ffffffff815534e0>] ? _raw_spin_unlock_irq+0x30/0x40 [<ffffffff815534e0>] ? _raw_spin_unlock_irq+0x30/0x40 [<ffffffff81550540>] wait_for_common+0x130/0x190 [<ffffffff81051920>] ? try_to_wake_up+0x510/0x510 [<ffffffff8155067d>] wait_for_completion+0x1d/0x20 [<ffffffff8107f36c>] kthread_create_on_node+0xac/0x150 [<ffffffff81077bb0>] ? process_scheduled_works+0x40/0x40 [<ffffffff8155045f>] ? wait_for_common+0x4f/0x190 [<ffffffff8107a283>] __alloc_workqueue_key+0x1a3/0x590 [<ffffffff81e0cce2>] cpuset_init_smp+0x6b/0x7b [<ffffffff81df3d07>] kernel_init+0xc3/0x182 [<ffffffff8155d5e4>] kernel_thread_helper+0x4/0x10 [<ffffffff81553cd4>] ? retint_restore_args+0x13/0x13 [<ffffffff81df3c44>] ? start_kernel+0x400/0x400 [<ffffffff8155d5e0>] ? gs_change+0x13/0x13 The divede by zero is caused by the following line, group->cpu_power==0: kernel/sched_fair.c::update_sg_lb_stats() /* Adjust by relative CPU power of the group */ sgs->avg_load = (sgs->group_load * SCHED_LOAD_SCALE) / group->cpu_power; This regression was caused by commit e23bba6044 ("x86-64, NUMA: Unify emulated distance mapping") because it changes cpu -> node mapping in the process of dropping fake_physnodes(). old) all cpus are assinged node 0 now) cpus are assigned round robin (the logic is implemented by numa_init_array()) Note: The change in behavior only happens if the system doesn't have neither ACPI SRAT table nor AMD northbridge NUMA information. Round robin assignment doesn't work because init_numa_sched_groups_power() assumes all logical cpus in the same physical cpu share the same node (then it only accounts for group_first_cpu()), and the simple round robin breaks the above assumption. Thus, this patch implements a reassignment of node-ids if buggy firmware or numa emulation makes wrong cpu node map. Tt enforce all logical cpus in the same physical cpu share the same node. Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Brian Gerst <brgerst@gmail.com> Cc: Cyrill Gorcunov <gorcunov@gmail.com> Cc: Shaohui Zheng <shaohui.zheng@intel.com> Cc: David Rientjes <rientjes@google.com> Cc: H. Peter Anvin <hpa@linux.intel.com> Link: http://lkml.kernel.org/r/20110415203928.1303.A69D9226@jp.fujitsu.com Signed-off-by: Ingo Molnar <mingo@elte.hu>		2011-04-15 20:28:19 +02:00
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