From: Mikulas Patocka mpatocka@redhat.com
commit 6ba688364856ad083be537f08e86ba97f433d405 upstream.
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 mpatocka@redhat.com Cc: stable@vger.kernel.org # v5.18 Signed-off-by: Helge Deller deller@gmx.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/parisc/kernel/processor.c | 2 -- arch/parisc/kernel/topology.c | 16 +--------------- 2 files changed, 1 insertion(+), 17 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 */
diff --git a/arch/parisc/kernel/topology.c b/arch/parisc/kernel/topology.c index 9696e3cb6a2a..b9d845e314f8 100644 --- a/arch/parisc/kernel/topology.c +++ b/arch/parisc/kernel/topology.c @@ -20,8 +20,6 @@
static DEFINE_PER_CPU(struct cpu, cpu_devices);
-static int dualcores_found; - /* * store_cpu_topology is called at boot when only one cpu is running * and with the mutex cpu_hotplug.lock locked, when several cpus have booted, @@ -60,7 +58,6 @@ void store_cpu_topology(unsigned int cpuid) if (p->cpu_loc) { cpuid_topo->core_id++; cpuid_topo->package_id = cpu_topology[cpu].package_id; - dualcores_found = 1; continue; } } @@ -80,22 +77,11 @@ void store_cpu_topology(unsigned int cpuid) cpu_topology[cpuid].package_id); }
-static struct sched_domain_topology_level parisc_mc_topology[] = { -#ifdef CONFIG_SCHED_MC - { cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) }, -#endif - - { cpu_cpu_mask, SD_INIT_NAME(DIE) }, - { NULL, }, -}; - /* * init_cpu_topology is called at boot when only one cpu is running * which prevent simultaneous write access to cpu_topology array */ void __init init_cpu_topology(void) { - /* Set scheduler topology descriptor */ - if (dualcores_found) - set_sched_topology(parisc_mc_topology); + reset_cpu_topology(); }