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authorIngo Molnar <mingo@elte.hu>2009-09-04 05:49:25 -0400
committerIngo Molnar <mingo@elte.hu>2009-09-04 05:52:52 -0400
commitd7ea17a76916e456fcc78e45142c66f7fb875e3d (patch)
treebe8422a0c60216991ccd98923fe13547738ab354 /kernel/sched.c
parent18a3885fc1ffa92c2212ff0afdf033403d5b0fa0 (diff)
sched: Fix dynamic power-balancing crash
This crash: [ 1774.088275] divide error: 0000 [#1] SMP [ 1774.100355] CPU 13 [ 1774.102498] Modules linked in: [ 1774.105631] Pid: 30881, comm: hackbench Not tainted 2.6.31-rc8-tip-01308-g484d664-dirty #1629 X8DTN [ 1774.114807] RIP: 0010:[<ffffffff81041c38>] [<ffffffff81041c38>] sched_balance_self+0x19b/0x2d4 Triggers because update_group_power() modifies the sd tree and does temporary calculations there - not considering that other CPUs could observe intermediate values, such as the zero initial value. Calculate it in a temporary variable instead. (we need no memory barrier as these are all statistical values anyway) Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Mike Galbraith <efault@gmx.de> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> LKML-Reference: <20090904092742.GA11014@elte.hu> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched.c')
-rw-r--r--kernel/sched.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index b53785346850..796baf731976 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3765,19 +3765,22 @@ static void update_group_power(struct sched_domain *sd, int cpu)
3765{ 3765{
3766 struct sched_domain *child = sd->child; 3766 struct sched_domain *child = sd->child;
3767 struct sched_group *group, *sdg = sd->groups; 3767 struct sched_group *group, *sdg = sd->groups;
3768 unsigned long power;
3768 3769
3769 if (!child) { 3770 if (!child) {
3770 update_cpu_power(sd, cpu); 3771 update_cpu_power(sd, cpu);
3771 return; 3772 return;
3772 } 3773 }
3773 3774
3774 sdg->cpu_power = 0; 3775 power = 0;
3775 3776
3776 group = child->groups; 3777 group = child->groups;
3777 do { 3778 do {
3778 sdg->cpu_power += group->cpu_power; 3779 power += group->cpu_power;
3779 group = group->next; 3780 group = group->next;
3780 } while (group != child->groups); 3781 } while (group != child->groups);
3782
3783 sdg->cpu_power = power;
3781} 3784}
3782 3785
3783/** 3786/**