sched: Fix hotplug vs. set_cpus_allowed_ptr()

Lai found that:

  WARNING: CPU: 1 PID: 13 at arch/x86/kernel/smp.c:124 native_smp_send_reschedule+0x2d/0x4b()
  ...
  migration_cpu_stop+0x1d/0x22

was caused by set_cpus_allowed_ptr() assuming that cpu_active_mask is
always a sub-set of cpu_online_mask.

This isn't true since 5fbd036 ("sched: Cleanup cpu_active madness").

So set active and online at the same time to avoid this particular
problem.

Fixes: 5fbd036 ("sched: Cleanup cpu_active madness")
Signed-off-by: Lai Jiangshan <[email protected]>
Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Gautham R. Shenoy <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Michael wang <[email protected]>
Cc: Paul Gortmaker <[email protected]>
Cc: Rafael J. Wysocki <[email protected]>
Cc: Srivatsa S. Bhat <[email protected]>
Cc: Toshi Kani <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: Lai Jiangshan

kernel/cpu.c

@@ -726,10 +726,12 @@ void set_cpu_present(unsigned int cpu, bool present)
 
 void set_cpu_online(unsigned int cpu, bool online)
 {
-	if (online)
+	if (online) {
 		cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
-	else
+		cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
+	} else {
 		cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
+	}
 }
 
 void set_cpu_active(unsigned int cpu, bool active)

kernel/sched/core.c

@@ -5076,7 +5076,6 @@ static int sched_cpu_active(struct notifier_block *nfb,
 				      unsigned long action, void *hcpu)
 {
 	switch (action & ~CPU_TASKS_FROZEN) {
-	case CPU_STARTING:
 	case CPU_DOWN_FAILED:
 		set_cpu_active((long)hcpu, true);
 		return NOTIFY_OK;