From 6ba688364856ad083be537f08e86ba97f433d405 Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Wed, 1 Jun 2022 13:18:22 -0400 Subject: 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 Cc: stable@vger.kernel.org # v5.18 Signed-off-by: Helge Deller --- arch/parisc/kernel/processor.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'arch/parisc/kernel/processor.c') 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 */ -- cgit v1.2.3