ARM: SMP: use a timing out completion for cpu hotplug

Rather than open-coding the jiffy-based wait, and polling for the
secondary CPU to come online, use a completion instead.  This
removes the need to poll, instead we will be notified when the
secondary CPU has initialized.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/smp.c

@@ -58,6 +58,8 @@ enum ipi_msg_type {
 	IPI_CPU_STOP,
 };
 
+static DECLARE_COMPLETION(cpu_running);
+
 int __cpuinit __cpu_up(unsigned int cpu)
 {
 	struct cpuinfo_arm *ci = &per_cpu(cpu_data, cpu);
@@ -98,20 +100,12 @@ int __cpuinit __cpu_up(unsigned int cpu)
 	 */
 	ret = boot_secondary(cpu, idle);
 	if (ret == 0) {
-		unsigned long timeout;
-
 		/*
 		 * CPU was successfully started, wait for it
 		 * to come online or time out.
 		 */
-		timeout = jiffies + HZ;
-		while (time_before(jiffies, timeout)) {
-			if (cpu_online(cpu))
-				break;
-
-			udelay(10);
-			barrier();
-		}
+		wait_for_completion_timeout(&cpu_running,
+						 msecs_to_jiffies(1000));
 
 		if (!cpu_online(cpu)) {
 			pr_crit("CPU%u: failed to come online\n", cpu);
@@ -300,9 +294,10 @@ asmlinkage void __cpuinit secondary_start_kernel(void)
 	/*
 	 * OK, now it's safe to let the boot CPU continue.  Wait for
 	 * the CPU migration code to notice that the CPU is online
-	 * before we continue.
+	 * before we continue - which happens after __cpu_up returns.
 	 */
 	set_cpu_online(cpu, true);
+	complete(&cpu_running);
 
 	/*
 	 * Setup the percpu timer for this CPU.