From 7d6b46707f2491a94f4bd3b4329d2d7f809e9368 Mon Sep 17 00:00:00 2001 From: KOSAKI Motohiro Date: Fri, 15 Apr 2011 20:39:01 +0900 Subject: [PATCH] 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: [] find_busiest_group+0x38c/0xd30 [] ? local_clock+0x6f/0x80 [] load_balance+0xa3/0x600 [] idle_balance+0xf3/0x180 [] schedule+0x722/0x7d0 [] ? wait_for_common+0x128/0x190 [] schedule_timeout+0x265/0x320 [] ? lock_release_holdtime+0x35/0x1a0 [] ? wait_for_common+0x128/0x190 [] ? __lock_release+0x9c/0x1d0 [] ? _raw_spin_unlock_irq+0x30/0x40 [] ? _raw_spin_unlock_irq+0x30/0x40 [] wait_for_common+0x130/0x190 [] ? try_to_wake_up+0x510/0x510 [] wait_for_completion+0x1d/0x20 [] kthread_create_on_node+0xac/0x150 [] ? process_scheduled_works+0x40/0x40 [] ? wait_for_common+0x4f/0x190 [] __alloc_workqueue_key+0x1a3/0x590 [] cpuset_init_smp+0x6b/0x7b [] kernel_init+0xc3/0x182 [] kernel_thread_helper+0x4/0x10 [] ? retint_restore_args+0x13/0x13 [] ? start_kernel+0x400/0x400 [] ? 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 Acked-by: Tejun Heo Cc: Yinghai Lu Cc: Brian Gerst Cc: Cyrill Gorcunov Cc: Shaohui Zheng Cc: David Rientjes Cc: H. Peter Anvin Link: http://lkml.kernel.org/r/20110415203928.1303.A69D9226@jp.fujitsu.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/smpboot.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index c2871d3c71b6..8ed8908cc9f7 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -312,6 +312,26 @@ void __cpuinit smp_store_cpu_info(int id) identify_secondary_cpu(c); } +static void __cpuinit check_cpu_siblings_on_same_node(int cpu1, int cpu2) +{ + int node1 = early_cpu_to_node(cpu1); + int node2 = early_cpu_to_node(cpu2); + + /* + * Our CPU scheduler assumes all logical cpus in the same physical cpu + * share the same node. But, buggy ACPI or NUMA emulation might assign + * them to different node. Fix it. + */ + if (node1 != node2) { + pr_warning("CPU %d in node %d and CPU %d in node %d are in the same physical CPU. forcing same node %d\n", + cpu1, node1, cpu2, node2, node2); + + numa_remove_cpu(cpu1); + numa_set_node(cpu1, node2); + numa_add_cpu(cpu1); + } +} + static void __cpuinit link_thread_siblings(int cpu1, int cpu2) { cpumask_set_cpu(cpu1, cpu_sibling_mask(cpu2)); @@ -320,6 +340,7 @@ static void __cpuinit link_thread_siblings(int cpu1, int cpu2) cpumask_set_cpu(cpu2, cpu_core_mask(cpu1)); cpumask_set_cpu(cpu1, cpu_llc_shared_mask(cpu2)); cpumask_set_cpu(cpu2, cpu_llc_shared_mask(cpu1)); + check_cpu_siblings_on_same_node(cpu1, cpu2); } @@ -361,10 +382,12 @@ void __cpuinit set_cpu_sibling_map(int cpu) per_cpu(cpu_llc_id, cpu) == per_cpu(cpu_llc_id, i)) { cpumask_set_cpu(i, cpu_llc_shared_mask(cpu)); cpumask_set_cpu(cpu, cpu_llc_shared_mask(i)); + check_cpu_siblings_on_same_node(cpu, i); } if (c->phys_proc_id == cpu_data(i).phys_proc_id) { cpumask_set_cpu(i, cpu_core_mask(cpu)); cpumask_set_cpu(cpu, cpu_core_mask(i)); + check_cpu_siblings_on_same_node(cpu, i); /* * Does this new cpu bringup a new core? */ -- 2.39.2