The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From a052096bdd6809eeab809202726634d1ac975aa1 Mon Sep 17 00:00:00 2001
From: Sven Schnelle svens@linux.ibm.com Date: Fri, 27 Aug 2021 20:21:05 +0200 Subject: [PATCH] s390/topology: fix topology information when calling cpu hotplug notifiers
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
diff --git a/arch/s390/include/asm/smp.h b/arch/s390/include/asm/smp.h index e317fd4866c1..f16f4d054ae2 100644 --- 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);
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c index 2a991e43ead3..1a04e5bdf655 100644 --- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -95,6 +95,7 @@ __vector128 __initdata boot_cpu_vector_save_area[__NUM_VXRS]; #endif
static unsigned int smp_max_threads __initdata = -1U; +cpumask_t cpu_setup_mask;
static int __init early_nosmt(char *s) { @@ -902,13 +903,14 @@ static void smp_start_secondary(void *cpuvoid) 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); @@ -950,10 +952,13 @@ early_param("possible_cpus", _setup_possible_cpus); 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(); diff --git a/arch/s390/kernel/topology.c b/arch/s390/kernel/topology.c index d2458a29618f..58f8291950cb 100644 --- a/arch/s390/kernel/topology.c +++ b/arch/s390/kernel/topology.c @@ -67,7 +67,7 @@ static void cpu_group_map(cpumask_t *dst, struct mask_info *info, unsigned int c 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, struct mask_info *info, unsigned int c 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 *dst, unsigned int cpu) 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); }