parisc: fix a crash with multicore scheduler

With the kernel 5.18, the system will hang on boot if it is compiled with
CONFIG_SCHED_MC. The last printed message is "Brought up 1 node, 1 CPU".

The crash happens in sd_init
tl->mask (which is cpu_coregroup_mask) returns an empty mask. This happens
	because cpu_topology[0].core_sibling is empty.
Consequently, sd_span is set to an empty mask
sd_id = cpumask_first(sd_span) sets sd_id == NR_CPUS (because the mask is
	empty)
sd->shared = *per_cpu_ptr(sdd->sds, sd_id); sets sd->shared to NULL
	because sd_id is out of range
atomic_inc(&sd->shared->ref); crashes without printing anything

We can fix it by calling reset_cpu_topology() from init_cpu_topology() -
this will initialize the sibling masks on CPUs, so that they're not empty.

This patch also removes the variable "dualcores_found", it is useless,
because during boot, init_cpu_topology is called before
store_cpu_topology. Thus, set_sched_topology(parisc_mc_topology) is never
called. We don't need to call it at all because default_topology in
kernel/sched/topology.c contains the same items as parisc_mc_topology.

Note that we should not call store_cpu_topology() from init_per_cpu()
because it is called too early in the kernel initialization process and it
results in the message "Failure to register CPU0 device". Before this
patch, store_cpu_topology() would exit immediatelly because
cpuid_topo->core id was uninitialized and it was 0.

Signed-off-by: Mikulas Patocka <[email protected]>
Cc: [email protected]	# v5.18
Signed-off-by: Helge Deller <[email protected]>

1 files changed, 0 insertions, 2 deletions

diff --git a/arch/parisc/kernel/processor.c b/arch/parisc/kernel/processor.c
index 26eb568f8b96..dddaaa6e7a82 100644
--- a/arch/parisc/kernel/processor.c
+++ b/arch/parisc/kernel/processor.c
@@ -327,8 +327,6 @@ int init_per_cpu(int cpunum)
 	set_firmware_width();
 	ret = pdc_coproc_cfg(&coproc_cfg);
 
-	store_cpu_topology(cpunum);
-
 	if(ret >= 0 && coproc_cfg.ccr_functional) {
 		mtctl(coproc_cfg.ccr_functional, 10);  /* 10 == Coprocessor Control Reg */