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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>
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1 changed files with 5 additions and 2 deletions
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@ -3765,19 +3765,22 @@ static void update_group_power(struct sched_domain *sd, int cpu)
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{
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{
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struct sched_domain *child = sd->child;
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struct sched_domain *child = sd->child;
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struct sched_group *group, *sdg = sd->groups;
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struct sched_group *group, *sdg = sd->groups;
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unsigned long power;
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if (!child) {
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if (!child) {
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update_cpu_power(sd, cpu);
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update_cpu_power(sd, cpu);
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return;
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return;
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}
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}
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sdg->cpu_power = 0;
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power = 0;
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group = child->groups;
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group = child->groups;
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do {
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do {
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sdg->cpu_power += group->cpu_power;
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power += group->cpu_power;
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group = group->next;
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group = group->next;
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} while (group != child->groups);
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} while (group != child->groups);
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sdg->cpu_power = power;
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}
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}
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/**
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/**
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