[RFC PATCH v2 07/10] kick_process(),cpu-hotplug: Prevent offlining of target CPU properly

From: Srivatsa S. Bhat
Date: Wed Dec 05 2012 - 13:45:36 EST

Once stop_machine() is gone from the CPU offline path, we won't be able to
depend on preempt_disable() to prevent CPUs from going offline from under us.

Use the get/put_online_cpus_atomic_light() APIs to prevent changes to the
cpu_online_mask, while invoking from atomic context.

Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>

kernel/sched/core.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c9a331e..84a8579 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1091,11 +1091,11 @@ void kick_process(struct task_struct *p)
int cpu;

- preempt_disable();
+ get_online_cpus_atomic_light();
cpu = task_cpu(p);
if ((cpu != smp_processor_id()) && task_curr(p))
- preempt_enable();
+ put_online_cpus_atomic_light();
#endif /* CONFIG_SMP */

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