On Tue, 31 May 2022, Helge Deller wrote: > Mikulas noticed that the parisc kernel crashes in sd_init() if > CONFIG_SCHED_MC is enabled. > Multicore-scheduling is probably not very useful on parisc, so simply > drop this option. > > Signed-off-by: Helge Deller <deller@xxxxxx> > Noticed-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> # 5.18 Hi I think that we should fix the root cause instead of trying to treat the symptoms. Some more testing showed that: in sd_init: tl->mask(cpu) returns an empty mask tl->mask is cpu_coregroup_mask in cpu_coregroup_mask: cpu_topology[cpu].core_sibling is an empty mask, that gets returned to sd_init In arch/parisc/kernel/topology.c: init_cpu_topology is called before store_cpu_topology, but it depends on the variable dualcores_found being set by store_cpu_topology. Thus, it is not set. store_cpu_topology returns if cpuid_topo->core_id != -1, but during boot, store_cpu_topology is called before reset_cpu_topology, thus the member "core_id" is uninitialized zero and store_cpu_tolopogy does nothing. If these issues are addrssed, multicore scheduling will work. Mikulas
