Merge branch 'sched/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched/for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: hrtick_enabled() should use cpu_active()
  sched, x86: clean up hrtick implementation
  sched: fix build error, provide partition_sched_domains() unconditionally
  sched: fix warning in inc_rt_tasks() to not declare variable 'rq' if it's not needed
  cpu hotplug: Make cpu_active_map synchronization dependency clear
  cpu hotplug, sched: Introduce cpu_active_map and redo sched domain managment (take 2)
  sched: rework of "prioritize non-migratable tasks over migratable ones"
  sched: reduce stack size in isolated_cpu_setup()
  Revert parts of "ftrace: do not trace scheduler functions"

Fixed up conflicts in include/asm-x86/thread_info.h (due to the
TIF_SINGLESTEP unification vs TIF_HRTICK_RESCHED removal) and
kernel/sched_fair.c (due to cpu_active_map vs for_each_cpu_mask_nr()
introduction).

1 files changed, 34 insertions, 6 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index d26d0b095b3..2cc409ce0a8 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -64,6 +64,8 @@ void __init cpu_hotplug_init(void)
 	cpu_hotplug.refcount = 0;
 }
 
+cpumask_t cpu_active_map;
+
 #ifdef CONFIG_HOTPLUG_CPU
 
 void get_online_cpus(void)
@@ -291,11 +293,30 @@ int __ref cpu_down(unsigned int cpu)
 	int err = 0;
 
 	cpu_maps_update_begin();
-	if (cpu_hotplug_disabled)
+
+	if (cpu_hotplug_disabled) {
 		err = -EBUSY;
-	else
-		err = _cpu_down(cpu, 0);
+		goto out;
+	}
+
+	cpu_clear(cpu, cpu_active_map);
+
+	/*
+	 * Make sure the all cpus did the reschedule and are not
+	 * using stale version of the cpu_active_map.
+	 * This is not strictly necessary becuase stop_machine()
+	 * that we run down the line already provides the required
+	 * synchronization. But it's really a side effect and we do not
+	 * want to depend on the innards of the stop_machine here.
+	 */
+	synchronize_sched();
+
+	err = _cpu_down(cpu, 0);
 
+	if (cpu_online(cpu))
+		cpu_set(cpu, cpu_active_map);
+
+out:
 	cpu_maps_update_done();
 	return err;
 }
@@ -355,11 +376,18 @@ int __cpuinit cpu_up(unsigned int cpu)
 	}
 
 	cpu_maps_update_begin();
-	if (cpu_hotplug_disabled)
+
+	if (cpu_hotplug_disabled) {
 		err = -EBUSY;
-	else
-		err = _cpu_up(cpu, 0);
+		goto out;
+	}
+
+	err = _cpu_up(cpu, 0);
 
+	if (cpu_online(cpu))
+		cpu_set(cpu, cpu_active_map);
+
+out:
 	cpu_maps_update_done();
 	return err;
 }