sched: re-add removed arch_update_cpu_topology call
cover sched: re-add removed arch_update_cpu_topology call
This fixes a regression introduced with e761b7725234276a802322549cee5255305a0930 ("cpu hotplug, sched:
Introduce cpu_active_map and redo sched domain managment (take 2)":
arch_reinit_sched_domains used to call arch_update_cpu_topology via arch_init_sched_domains. This call got lost with the above mentioned patch.
So we might end up with outdated and missing cpus in the cpu core maps (s390 used to call arch_reinit_sched_domains if cpu topology changed).
This patch set changes arch_update_cpu_topology so that it can indicate if the cpu topology changed and adds a call to arch_update_cpu_topology in partition_sched_domains which gets called whenever scheduling domains get updated.
So whenever architecture code detects that cpu topology changed it might force an update of the scheduling domains by calling arch_reinit_sched_domains or rebuild_sched_domains.
Besides that the first patch also adds a comment to arch_update_cpu_topology so that its purpose gets described, since most people seem to expect that cpu core mappings are stable which isn't necessarily the case.
PATCH 1/2 sched: let arch_update_cpu_topology indicate if topology changed
From: Heiko Carstens <[email protected]>
Change arch_update_cpu_topology so it returns 1 if the cpu topology changed and 0 if it didn't change. This will be useful for the next patch which adds a call to this function in partition_sched_domains.
--- arch/s390/kernel/topology.c | 5 +++-- include/linux/topology.h | 2 +- kernel/sched.c | 8 +++++++- 3 files changed, 11 insertions(+), 4 deletions(-)
kernel/sched.c +7 -1
@@ -7712,8 +7712,14 @@ static struct sched_domain_attr *dattr_c*/ static cpumask_t fallback_doms; -void __attribute__((weak))arch_update_cpu_topology (void ) +/* +* arch_update_cpu_topology lets virtualized architectures update the +* cpu core maps. It is supposed to return 1 if the topology changed +* or 0 if it stayed the same. +*/ +int __attribute__((weak))arch_update_cpu_topology (void ) { +return 0 ; }/*
arch/s390/kernel/topology.c +3 -2
@@ -212,7 +212,7 @@ static void update_cpu_core_map(void) cpu_core_map[cpu] =cpu_coregroup_map (cpu); } -void arch_update_cpu_topology (void ) +int arch_update_cpu_topology (void ) {struct tl_info *info = tl_info;struct sys_device *sysdev;
@@ -221,7 +221,7 @@ void arch_update_cpu_topology(void)if (!machine_has_topology) {update_cpu_core_map ();topology_update_polarization_simple (); -return ; +return 0 ; }stsi (info,15 ,1 ,2 );tl_to_cores (info);
@@ -230,6 +230,7 @@ void arch_update_cpu_topology(void) sysdev =get_cpu_sysdev (cpu);kobject_uevent (&sysdev->kobj,KOBJ_CHANGE ); } +return 1 ; }static void topology_work_fn (struct work_struct *work)
include/linux/topology.h +1 -1
@@ -49,7 +49,7 @@ for_each_online_node(node) \ if (nr_cpus_node(node)) -void arch_update_cpu_topology(void); +int arch_update_cpu_topology(void);/* Conform to ACPI 2.0 SLIT distance definitions */ #define LOCAL_DISTANCE 10
PATCH 2/2 sched: re-add missing arch_update_cpu_topology call
In reply to Heiko CarstensFrom: Heiko Carstens <[email protected]>
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.
--- kernel/sched.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
kernel/sched.c +6 -2
@@ -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;