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Subject[PATCH/RESEND 2/2] sched: re-add missing arch_update_cpu_topology call
From: Heiko Carstens <heiko.carstens@de.ibm.com>

arch_reinit_sched_domains used to call arch_update_cpu_topology
via arch_init_sched_domains. This call got lost with
e761b7725234276a802322549cee5255305a0930 ("cpu hotplug, sched: Introduce
cpu_active_map and redo sched domain managment (take 2)".

So we might end up with outdated and missing cpus in the cpu core
maps (architecture used to call arch_reinit_sched_domains if cpu
topology changed).

This adds a call to arch_update_cpu_topology in partition_sched_domains
which gets called whenever scheduling domains get updated. Which is
what is supposed to happen when cpu topology changes.

Since arch_update_cpu_topology returns 0 if the cpu topology didn't
change this is a NOP for all architectures but s390 (currently).

If arch_update_cpu_topology returns 1 this causes all scheduling domains
to be destroyed and rebuilt.

Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
---
kernel/sched.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -7813,17 +7813,21 @@ void partition_sched_domains(int ndoms_n
struct sched_domain_attr *dattr_new)
{
int i, j, n;
+ int top_changed;

mutex_lock(&sched_domains_mutex);

/* always unregister in case we don't destroy any domains */
unregister_sched_domain_sysctl();

+ /* Let architecture update cpu core mappings. */
+ top_changed = arch_update_cpu_topology();
+
n = doms_new ? ndoms_new : 0;

/* Destroy deleted domains */
for (i = 0; i < ndoms_cur; i++) {
- for (j = 0; j < n; j++) {
+ for (j = 0; j < n && !top_changed; j++) {
if (cpus_equal(doms_cur[i], doms_new[j])
&& dattrs_equal(dattr_cur, i, dattr_new, j))
goto match1;
@@ -7843,7 +7847,7 @@ match1:

/* Build new domains */
for (i = 0; i < ndoms_new; i++) {
- for (j = 0; j < ndoms_cur; j++) {
+ for (j = 0; j < ndoms_cur && !top_changed; j++) {
if (cpus_equal(doms_new[i], doms_cur[j])
&& dattrs_equal(dattr_new, i, dattr_cur, j))
goto match2;
--


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