From patchwork series 435232

https://patchwork.ozlabs.org//project/linuxppc-dev/list/?series=435232

Author: Fox Snowpatch

arch/s390/include/asm/topology.h

@@ -99,6 +99,9 @@ static inline int numa_node_id(void)
 
 #endif /* CONFIG_NUMA */
 
+#define arch_cpu_parked cpu_parked
+int cpu_parked(int cpu);
+
 #include <asm-generic/topology.h>
 
 #endif /* _ASM_S390_TOPOLOGY_H */

arch/s390/kernel/topology.c

@@ -299,6 +299,11 @@ void store_topology(struct sysinfo_15_1_x *info)
 	stsi(info, 15, 1, topology_mnest_limit());
 }
 
+int cpu_parked(int cpu)
+{
+	return smp_cpu_get_polarization(cpu) == POLARIZATION_VL;
+}
+
 static void __arch_update_dedicated_flag(void *arg)
 {
 	if (topology_cpu_dedicated(smp_processor_id()))

include/linux/sched/topology.h

@@ -270,6 +270,26 @@ unsigned long arch_scale_cpu_capacity(int cpu)
 }
 #endif
 
+#ifndef arch_cpu_parked
+/**
+ * arch_cpu_parked - Check if a given CPU is currently parked.
+ *
+ * A parked CPU cannot run any kind of workload since underlying
+ * physical CPU should not be used at the moment .
+ *
+ * @cpu: the CPU in question.
+ *
+ * By default assume CPU is not parked
+ *
+ * Return: Parked state of CPU
+ */
+static __always_inline
+unsigned long arch_cpu_parked(int cpu)
+{
+	return false;
+}
+#endif
+
 #ifndef arch_scale_hw_pressure
 static __always_inline
 unsigned long arch_scale_hw_pressure(int cpu)

kernel/sched/core.c

@@ -2435,7 +2435,7 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
 
 	/* Non kernel threads are not allowed during either online or offline. */
 	if (!(p->flags & PF_KTHREAD))
-		return cpu_active(cpu);
+		return !arch_cpu_parked(cpu) && cpu_active(cpu);
 
 	/* KTHREAD_IS_PER_CPU is always allowed. */
 	if (kthread_is_per_cpu(p))
@@ -2445,6 +2445,10 @@ static inline bool is_cpu_allowed(struct task_struct *p, int cpu)
 	if (cpu_dying(cpu))
 		return false;
 
+	/* CPU should be avoided at the moment */
+	if (arch_cpu_parked(cpu))
+		return false;
+
 	/* But are allowed during online. */
 	return cpu_online(cpu);
 }
@@ -3922,6 +3926,10 @@ static inline bool ttwu_queue_cond(struct task_struct *p, int cpu)
 	if (task_on_scx(p))
 		return false;
 
+	/* The task should not be queued onto a parked CPU. */
+	if (arch_cpu_parked(cpu))
+		return false;
+
 	/*
 	 * Do not complicate things with the async wake_list while the CPU is
 	 * in hotplug state.