[ARM SMP] Track CPU idle threads

Track the idle thread task_struct for each CPU.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

2 files changed, 14 insertions, 7 deletions

diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c
index 826164945747..45877f5d5717 100644
--- a/arch/arm/kernel/smp.c
+++ b/arch/arm/kernel/smp.c
@@ -80,19 +80,23 @@ static DEFINE_SPINLOCK(smp_call_function_lock);
 
 int __cpuinit __cpu_up(unsigned int cpu)
 {
-        struct task_struct *idle;
+        struct cpuinfo_arm *ci = &per_cpu(cpu_data, cpu);
+        struct task_struct *idle = ci->idle;
         pgd_t *pgd;
         pmd_t *pmd;
         int ret;
 
         /*
-         * Spawn a new process manually.  Grab a pointer to
-         * its task struct so we can mess with it
+         * Spawn a new process manually, if not already done.
+         * Grab a pointer to its task struct so we can mess with it
          */
-        idle = fork_idle(cpu);
-        if (IS_ERR(idle)) {
-                printk(KERN_ERR "CPU%u: fork() failed\n", cpu);
-                return PTR_ERR(idle);
+        if (!idle) {
+                idle = fork_idle(cpu);
+                if (IS_ERR(idle)) {
+                        printk(KERN_ERR "CPU%u: fork() failed\n", cpu);
+                        return PTR_ERR(idle);
+                }
+                ci->idle = idle;
         }
 
         /*
@@ -236,6 +240,8 @@ void __init smp_prepare_boot_cpu(void)
 {
         unsigned int cpu = smp_processor_id();
 
+        per_cpu(cpu_data, cpu).idle = current;
+
         cpu_set(cpu, cpu_possible_map);
         cpu_set(cpu, cpu_present_map);
         cpu_set(cpu, cpu_online_map);
diff --git a/include/asm-arm/cpu.h b/include/asm-arm/cpu.h
index fcbdd40cb667..751bc7462074 100644
--- a/include/asm-arm/cpu.h
+++ b/include/asm-arm/cpu.h
@@ -16,6 +16,7 @@
 struct cpuinfo_arm {
         struct cpu      cpu;
 #ifdef CONFIG_SMP
+        struct task_struct *idle;
         unsigned int    loops_per_jiffy;
 #endif
 };