Re: [PATCH] [10/23] SCHED: Only allocate per cpu cpu mask buffer with offstack cpumasks

[Peter Zijlstra <peterz@infradead.org>]

On Thu, 2010-06-10 at 16:52 +0200, Andi Kleen wrote:
> > This patch will actually break things.. please read the code.
> > 
> > I guess we could move the unsigned long into that block, but I really
> > don't see the point.
> 
> How does it break things? 
> 
> ptr is not used for anything unless that define is set. gcc doesn't
> lie on this.

        if (alloc_size) {
                ptr = (unsigned long)kzalloc(alloc_size, GFP_NOWAIT);

#ifdef CONFIG_FAIR_GROUP_SCHED
                init_task_group.se = (struct sched_entity **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

                init_task_group.cfs_rq = (struct cfs_rq **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

#endif /* CONFIG_FAIR_GROUP_SCHED */
#ifdef CONFIG_RT_GROUP_SCHED
                init_task_group.rt_se = (struct sched_rt_entity **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

                init_task_group.rt_rq = (struct rt_rq **)ptr;
                ptr += nr_cpu_ids * sizeof(void **);

#endif /* CONFIG_RT_GROUP_SCHED */
#ifdef CONFIG_CPUMASK_OFFSTACK
                for_each_possible_cpu(i) {
                        per_cpu(load_balance_tmpmask, i) = (void *)ptr;
                        ptr += cpumask_size();
                }
#endif /* CONFIG_CPUMASK_OFFSTACK */
        }