From 30b4e9eb783d94e9f5d503b15eb31720679ae1c7 Mon Sep 17 00:00:00 2001 From: Igor Mammedov Date: Wed, 9 May 2012 12:38:28 +0200 Subject: [PATCH] sched: Fix KVM and ia64 boot crash due to sched_groups circular linked list assumption If we have one cpu that failed to boot and boot cpu gave up on waiting for it and then another cpu is being booted, kernel might crash with following OOPS: BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 IP: [] __bitmap_weight+0x30/0x80 Call Trace: [] build_sched_domains+0x7b6/0xa50 The crash happens in init_sched_groups_power() that expects sched_groups to be circular linked list. However it is not always true, since sched_groups preallocated in __sdt_alloc are initialized in build_sched_groups and it may exit early if (cpu != cpumask_first(sched_domain_span(sd))) return 0; without initializing sd->groups->next field. Fix bug by initializing next field right after sched_group was allocated. Also-Reported-by: Jiang Liu Signed-off-by: Igor Mammedov Cc: a.p.zijlstra@chello.nl Cc: pjt@google.com Cc: seto.hidetoshi@jp.fujitsu.com Link: http://lkml.kernel.org/r/1336559908-32533-1-git-send-email-imammedo@redhat.com Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0533a688ce22..e5212ae294f6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6382,6 +6382,8 @@ static int __sdt_alloc(const struct cpumask *cpu_map) if (!sg) return -ENOMEM; + sg->next = sg; + *per_cpu_ptr(sdd->sg, j) = sg; sgp = kzalloc_node(sizeof(struct sched_group_power),