[PATCH v6 34/46] hexagon/smp: Use get/put_online_cpus_atomic() to prevent CPU offline

[Srivatsa S. Bhat]

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

Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
while invoking from atomic context.

Cc: Richard Kuo <rkuo at codeaurora.org>
Cc: linux-hexagon at vger.kernel.org
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat at linux.vnet.ibm.com>
---

 arch/hexagon/kernel/smp.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/hexagon/kernel/smp.c b/arch/hexagon/kernel/smp.c
index 8e095df..ec87de9 100644
--- a/arch/hexagon/kernel/smp.c
+++ b/arch/hexagon/kernel/smp.c
@@ -112,6 +112,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
 	unsigned long cpu;
 	unsigned long retval;
 
+	get_online_cpus_atomic();
 	local_irq_save(flags);
 
 	for_each_cpu(cpu, cpumask) {
@@ -128,6 +129,7 @@ void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
 	}
 
 	local_irq_restore(flags);
+	put_online_cpus_atomic();
 }
 
 static struct irqaction ipi_intdesc = {
@@ -241,9 +243,12 @@ void smp_send_reschedule(int cpu)
 void smp_send_stop(void)
 {
 	struct cpumask targets;
+
+	get_online_cpus_atomic();
 	cpumask_copy(&targets, cpu_online_mask);
 	cpumask_clear_cpu(smp_processor_id(), &targets);
 	send_ipi(&targets, IPI_CPU_STOP);
+	put_online_cpus_atomic();
 }
 
 void arch_send_call_function_single_ipi(int cpu)