[PATCH 5.14 401/432] s390/topology: fix topology information when calling cpu hotplug notifiers

Greg Kroah-Hartman
2021-09-16T17:52:05Z

From: Sven Schnelle <svens@linux.ibm.com>

commit a052096bdd6809eeab809202726634d1ac975aa1 upstream.

The cpu hotplug notifiers are called without updating the core/thread
masks when a new CPU is added. This causes problems with code setting
up data structures in a cpu hotplug notifier, and relying on that later
in normal code.

This caused a crash in the new core scheduling code (SCHED_CORE),
where rq->core was set up in a notifier depending on cpu masks.

To fix this, add a cpu_setup_mask which is used in update_cpu_masks()
instead of the cpu_online_mask to determine whether the cpu masks should
be set for a certain cpu. Also move update_cpu_masks() to update the
masks before calling notify_cpu_starting() so that the notifiers are
seeing the updated masks.

Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Cc: <stable@vger.kernel.org>
[hca@linux.ibm.com: get rid of cpu_online_mask handling]
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/s390/include/asm/smp.h | 1 +
arch/s390/kernel/smp.c | 9 +++++++--
arch/s390/kernel/topology.c | 13 +++++++------
3 files changed, 15 insertions(+), 8 deletions(-)

--- a/arch/s390/include/asm/smp.h
+++ b/arch/s390/include/asm/smp.h
@@ -18,6 +18,7 @@ extern struct mutex smp_cpu_state_mutex;
extern unsigned int smp_cpu_mt_shift;
extern unsigned int smp_cpu_mtid;
extern __vector128 __initdata boot_cpu_vector_save_area[__NUM_VXRS];
+extern cpumask_t cpu_setup_mask;

extern int __cpu_up(unsigned int cpu, struct task_struct *tidle);

--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -95,6 +95,7 @@ __vector128 __initdata boot_cpu_vector_s
#endif

static unsigned int smp_max_threads __initdata = -1U;
+cpumask_t cpu_setup_mask;

static int __init early_nosmt(char *s)
{
@@ -894,13 +895,14 @@ static void smp_init_secondary(void)
vtime_init();
vdso_getcpu_init();
pfault_init();
+ cpumask_set_cpu(cpu, &cpu_setup_mask);
+ update_cpu_masks();
notify_cpu_starting(cpu);
if (topology_cpu_dedicated(cpu))
set_cpu_flag(CIF_DEDICATED_CPU);
else
clear_cpu_flag(CIF_DEDICATED_CPU);
set_cpu_online(cpu, true);
- update_cpu_masks();
inc_irq_stat(CPU_RST);
local_irq_enable();
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
@@ -955,10 +957,13 @@ early_param("possible_cpus", _setup_poss
int __cpu_disable(void)
{
unsigned long cregs[16];
+ int cpu;

/* Handle possible pending IPIs */
smp_handle_ext_call();
- set_cpu_online(smp_processor_id(), false);
+ cpu = smp_processor_id();
+ set_cpu_online(cpu, false);
+ cpumask_clear_cpu(cpu, &cpu_setup_mask);
update_cpu_masks();
/* Disable pseudo page faults on this cpu. */
pfault_fini();
--- a/arch/s390/kernel/topology.c
+++ b/arch/s390/kernel/topology.c
@@ -67,7 +67,7 @@ static void cpu_group_map(cpumask_t *dst
static cpumask_t mask;

cpumask_clear(&mask);
- if (!cpu_online(cpu))
+ if (!cpumask_test_cpu(cpu, &cpu_setup_mask))
goto out;
cpumask_set_cpu(cpu, &mask);
switch (topology_mode) {
@@ -88,7 +88,7 @@ static void cpu_group_map(cpumask_t *dst
case TOPOLOGY_MODE_SINGLE:
break;
}
- cpumask_and(&mask, &mask, cpu_online_mask);
+ cpumask_and(&mask, &mask, &cpu_setup_mask);
out:
cpumask_copy(dst, &mask);
}
@@ -99,16 +99,16 @@ static void cpu_thread_map(cpumask_t *ds
int i;

cpumask_clear(&mask);
- if (!cpu_online(cpu))
+ if (!cpumask_test_cpu(cpu, &cpu_setup_mask))
goto out;
cpumask_set_cpu(cpu, &mask);
if (topology_mode != TOPOLOGY_MODE_HW)
goto out;
cpu -= cpu % (smp_cpu_mtid + 1);
- for (i = 0; i <= smp_cpu_mtid; i++)
- if (cpu_present(cpu + i))
+ for (i = 0; i <= smp_cpu_mtid; i++) {
+ if (cpumask_test_cpu(cpu + i, &cpu_setup_mask))
cpumask_set_cpu(cpu + i, &mask);
- cpumask_and(&mask, &mask, cpu_online_mask);
+ }
out:
cpumask_copy(dst, &mask);
}
@@ -569,6 +569,7 @@ void __init topology_init_early(void)
alloc_masks(info, &book_info, 2);
alloc_masks(info, &drawer_info, 3);
out:
+ cpumask_set_cpu(0, &cpu_setup_mask);
__arch_update_cpu_topology();
__arch_update_dedicated_flag(NULL);
}