Why are you cc'ing x86 and numa folks but not a single scheduler person when you're patching scheduler stuff?
On Tue, 2012-09-18 at 18:12 +0800, Tang Chen wrote: > Once array sched_domains_numa_masks is defined, it is never updated. > When a new cpu on a new node is onlined, Hmm, so there's hardware where you can boot with smaller nr_node_ids than possible.. I guess that makes sense. > the coincident member in > sched_domains_numa_masks is not initialized, and all the masks are 0. > As a result, the build_overlap_sched_groups() will initialize a NULL > sched_group for the new cpu on the new node, which will lead to kernel panic. <snip> > This patch registers a new notifier for cpu hotplug notify chain, and > updates sched_domains_numa_masks every time a new cpu is onlined or offlined. Urgh, more hotplug notifiers.. a well. > Signed-off-by: Tang Chen <[email protected]> > --- > kernel/sched/core.c | 62 > +++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 62 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index fbf1fd0..66b36ab 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -6711,6 +6711,14 @@ static void sched_init_numa(void) > * numbers. > */ > > + /* > + * Since sched_domains_numa_levels is also used in other functions as > + * an index for sched_domains_numa_masks[][], we should reset it here in > + * case sched_domains_numa_masks[][] fails to be initialized. And set it > + * to 'level' when sched_domains_numa_masks[][] is fully initialized. > + */ > + sched_domains_numa_levels = 0; This isn't strictly needed for this patch right? I don't see anybody calling sched_init_numa() a second time (although they should).. > sched_domains_numa_masks = kzalloc(sizeof(void *) * level, GFP_KERNEL); > if (!sched_domains_numa_masks) > return; > @@ -6765,11 +6773,64 @@ static void sched_init_numa(void) > } > > sched_domain_topology = tl; > + > + sched_domains_numa_levels = level; > +} > + > +static void sched_domains_numa_masks_set(int cpu) > +{ > + int i, j; > + int node = cpu_to_node(cpu); > + > + for (i = 0; i < sched_domains_numa_levels; i++) > + for (j = 0; j < nr_node_ids; j++) > + if (node_distance(j, node) <= > sched_domains_numa_distance[i]) > + cpumask_set_cpu(cpu, > sched_domains_numa_masks[i][j]); > +} > + > +static void sched_domains_numa_masks_clear(int cpu) > +{ > + int i, j; > + for (i = 0; i < sched_domains_numa_levels; i++) > + for (j = 0; j < nr_node_ids; j++) > + cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]); > +} Aside from the coding style nit of wanting braces over multi-line statements even though not strictly required, I really don't see how this could possibly be right.. We do this because nr_node_ids changed, right? This means the entire distance table grew/shrunk, which means we should do the level scan again. > @@ -7218,6 +7279,7 @@ void __init sched_init_smp(void) > mutex_unlock(&sched_domains_mutex); > put_online_cpus(); > > + hotcpu_notifier(sched_domains_numa_masks_update, > CPU_PRI_SCHED_ACTIVE); > hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE); > hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE); OK, so you really want your notifier to run before cpuset_cpu_active because otherwise you get that crash, yet you fail with the whole order thing.. You should not _ever_ rely on registration order. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
