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powerpc: VPHN topology change updates all siblings

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When an associativity level change is found for one thread, the
siblings threads need to be updated as well.  This is done today
for PRRN in stage_topology_update() but is missing for VPHN in
update_cpu_associativity_changes_mask().  This patch will correctly
update all thread siblings during a topology change.

Without this patch a topology update can result in a CPU in
init_sched_groups_power() getting stuck indefinitely in a loop.

This loop is built in build_sched_groups(). As a result of the thread
moving to a node separate from its siblings the struct sched_group will
have its next pointer set to point to itself rather than the sched_group
struct of the next thread.  This happens because we have a domain without
the SD_OVERLAP flag, which is correct, and a topology that doesn't conform
with reality (threads on the same core assigned to different numa nodes).
When this list is traversed by init_sched_groups_power() it will reach
the thread's sched_group structure and loop indefinitely; the cpu will
be stuck at this point.

The bug was exposed when VPHN was enabled in commit b7abef0 (v3.9).

Cc: <stable@vger.kernel.org> [v3.9+]
Reported-by: Jan Stancek <jstancek@redhat.com>
Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Robert Jennings 2013-07-24 20:13:21 -05:00 committed by Benjamin Herrenschmidt
parent 8d7c55d01e
commit 3be7db6ab4
2 changed files with 47 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/include/asm/smp.h
View File

@ -145,6 +145,10 @@ extern void __cpu_die(unsigned int cpu);
#define smp_setup_cpu_maps() #define smp_setup_cpu_maps()
static inline void inhibit_secondary_onlining(void) {} static inline void inhibit_secondary_onlining(void) {}
static inline void uninhibit_secondary_onlining(void) {} static inline void uninhibit_secondary_onlining(void) {}
static inline const struct cpumask *cpu_sibling_mask(int cpu)
{
return cpumask_of(cpu);
}
#endif /* CONFIG_SMP */ #endif /* CONFIG_SMP */

53
arch/powerpc/mm/numa.c
View File

@ -27,6 +27,7 @@
#include <linux/seq_file.h> #include <linux/seq_file.h>
#include <linux/uaccess.h> #include <linux/uaccess.h>
#include <linux/slab.h> #include <linux/slab.h>
#include <asm/cputhreads.h>
#include <asm/sparsemem.h> #include <asm/sparsemem.h>
#include <asm/prom.h> #include <asm/prom.h>
#include <asm/smp.h> #include <asm/smp.h>
@ -1318,7 +1319,8 @@ static int update_cpu_associativity_changes_mask(void)
} }
} }
if (changed) { if (changed) {
cpumask_set_cpu(cpu, changes); cpumask_or(changes, changes, cpu_sibling_mask(cpu));
cpu = cpu_last_thread_sibling(cpu);
} }
} }
@ -1426,7 +1428,7 @@ static int update_cpu_topology(void *data)
if (!data) if (!data)
return -EINVAL; return -EINVAL;
cpu = get_cpu(); cpu = smp_processor_id();
for (update = data; update; update = update->next) { for (update = data; update; update = update->next) {
if (cpu != update->cpu) if (cpu != update->cpu)
@ -1446,12 +1448,12 @@ static int update_cpu_topology(void *data)
*/ */
int arch_update_cpu_topology(void) int arch_update_cpu_topology(void)
{ {
unsigned int cpu, changed = 0; unsigned int cpu, sibling, changed = 0;
struct topology_update_data *updates, *ud; struct topology_update_data *updates, *ud;
unsigned int associativity[VPHN_ASSOC_BUFSIZE] = {0}; unsigned int associativity[VPHN_ASSOC_BUFSIZE] = {0};
cpumask_t updated_cpus; cpumask_t updated_cpus;
struct device *dev; struct device *dev;
int weight, i = 0; int weight, new_nid, i = 0;
weight = cpumask_weight(&cpu_associativity_changes_mask); weight = cpumask_weight(&cpu_associativity_changes_mask);
if (!weight) if (!weight)
@ -1464,20 +1466,47 @@ int arch_update_cpu_topology(void)
cpumask_clear(&updated_cpus); cpumask_clear(&updated_cpus);
for_each_cpu(cpu, &cpu_associativity_changes_mask) { for_each_cpu(cpu, &cpu_associativity_changes_mask) {
ud = &updates[i++]; /*
ud->cpu = cpu; * If siblings aren't flagged for changes, updates list
* will be too short. Skip on this update and set for next
* update.
*/
if (!cpumask_subset(cpu_sibling_mask(cpu),
&cpu_associativity_changes_mask)) {
pr_info("Sibling bits not set for associativity "
"change, cpu%d\n", cpu);
cpumask_or(&cpu_associativity_changes_mask,
&cpu_associativity_changes_mask,
cpu_sibling_mask(cpu));
cpu = cpu_last_thread_sibling(cpu);
continue;
}
/* Use associativity from first thread for all siblings */
vphn_get_associativity(cpu, associativity); vphn_get_associativity(cpu, associativity);
ud->new_nid = associativity_to_nid(associativity); new_nid = associativity_to_nid(associativity);
if (new_nid < 0 || !node_online(new_nid))
new_nid = first_online_node;
if (ud->new_nid < 0 || !node_online(ud->new_nid)) if (new_nid == numa_cpu_lookup_table[cpu]) {
ud->new_nid = first_online_node; cpumask_andnot(&cpu_associativity_changes_mask,
&cpu_associativity_changes_mask,
ud->old_nid = numa_cpu_lookup_table[cpu]; cpu_sibling_mask(cpu));
cpumask_set_cpu(cpu, &updated_cpus); cpu = cpu_last_thread_sibling(cpu);
continue;
}
for_each_cpu(sibling, cpu_sibling_mask(cpu)) {
ud = &updates[i++];
ud->cpu = sibling;
ud->new_nid = new_nid;
ud->old_nid = numa_cpu_lookup_table[sibling];
cpumask_set_cpu(sibling, &updated_cpus);
if (i < weight) if (i < weight)
ud->next = &updates[i]; ud->next = &updates[i];
} }
cpu = cpu_last_thread_sibling(cpu);
}
stop_machine(update_cpu_topology, &updates[0], &updated_cpus); stop_machine(update_cpu_topology, &updates[0], &updated_cpus);