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

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>
ougdata · Aug 19, 2012 · a1a50d6 · a1a50d6
1 parent 73e79f4
commit a1a50d6
Showing 1 changed file with 6 additions and 11 deletions.
diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
@@ -59,6 +59,8 @@ enum ipi_msg_type {
 	IPI_CPU_BACKTRACE,
 };
 
+static DECLARE_COMPLETION(cpu_running);
+
 int __cpuinit __cpu_up(unsigned int cpu)
 {
 	struct cpuinfo_arm *ci = &per_cpu(cpu_data, cpu);
@@ -118,20 +120,12 @@ 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);
@@ -331,9 +325,10 @@ 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.