Re: bad patch in sched.c

Rusty Russell
2009-01-10T12:05:01Z

On Saturday 10 January 2009 05:00:28 Mike Travis wrote:
>
> It appears that
>
> commit 6c99e9ad47d9c082bd096f42fb49e397b05d58a8
> Author: Rusty Russell <rusty@rustcorp.com.au>
> Date: Tue Nov 25 02:35:04 2008 +1030
>
> sched: convert struct sched_group/sched_domain cpumask_ts to variable bitmaps
>
> Impact: (future) size reduction for large NR_CPUS.
>
> We move the 'cpumask' member of sched_group to the end, so when we
> kmalloc it we can do a minimal allocation: saves space for small
> nr_cpu_ids but big CONFIG_NR_CPUS. Similar trick for 'span' in
> sched_domain.
>
> This isn't quite as good as converting to a cpumask_var_t, as some
> sched_groups are actually static, but it's safer: we don't have to
> figure out where to call alloc_cpumask_var/free_cpumask_var.
>
> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
>
>
> causes a panic in ia64 with NR_CPUS=1024.

Thanks, that focussed me on the right place. Does this fix it?

cpumask: fix CONFIG_NUMA=y sched.c

struct sched_domain is now a dangling structure; where we really want
static ones, we need to use static_sched_domain.

(As the FIXME in this file says, cpumask_var_t would be better, but
this code is hairy enough without trying to add initialization code to
the right places).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/kernel/sched.c b/kernel/sched.c
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -7282,10 +7282,10 @@ cpu_to_phys_group(int cpu, const struct
* groups, so roll our own. Now each node has its own list of groups which
* gets dynamically allocated.
*/
-static DEFINE_PER_CPU(struct sched_domain, node_domains);
+static DEFINE_PER_CPU(struct static_sched_domain, node_domains);
static struct sched_group ***sched_group_nodes_bycpu;

-static DEFINE_PER_CPU(struct sched_domain, allnodes_domains);
+static DEFINE_PER_CPU(struct static_sched_domain, allnodes_domains);
static DEFINE_PER_CPU(struct static_sched_group, sched_group_allnodes);

static int cpu_to_allnodes_group(int cpu, const struct cpumask *cpu_map,
@@ -7560,7 +7560,7 @@ static int __build_sched_domains(const s
#ifdef CONFIG_NUMA
if (cpumask_weight(cpu_map) >
SD_NODES_PER_DOMAIN*cpumask_weight(nodemask)) {
- sd = &per_cpu(allnodes_domains, i);
+ sd = &per_cpu(allnodes_domains, i).sg;
SD_INIT(sd, ALLNODES);
set_domain_attribute(sd, attr);
cpumask_copy(sched_domain_span(sd), cpu_map);
@@ -7570,7 +7570,7 @@ static int __build_sched_domains(const s
} else
p = NULL;

- sd = &per_cpu(node_domains, i);
+ sd = &per_cpu(node_domains, i).sd;
SD_INIT(sd, NODE);
set_domain_attribute(sd, attr);
sched_domain_node_span(cpu_to_node(i), sched_domain_span(sd));
@@ -7688,7 +7688,7 @@ static int __build_sched_domains(const s
for_each_cpu(j, nodemask) {
struct sched_domain *sd;

- sd = &per_cpu(node_domains, j);
+ sd = &per_cpu(node_domains, j).sd;
sd->groups = sg;
}
sg->__cpu_power = 0;