Simplify stop_machine

stop_machine creates a kthread which creates kernel threads.  We can
create those threads directly and simplify things a little.  Some care
must be taken with CPU hotunplug, which has special needs, but that code
seems more robust than it was in the past.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 3 insertions, 10 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 10ba5f1004a5..cf79bb911371 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -216,7 +216,6 @@ static int __ref take_cpu_down(void *_param)
 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 {
         int err, nr_calls = 0;
-        struct task_struct *p;
         cpumask_t old_allowed, tmp;
         void *hcpu = (void *)(long)cpu;
         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
@@ -250,19 +249,15 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
         cpu_clear(cpu, tmp);
         set_cpus_allowed_ptr(current, &tmp);
 
-        p = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
+        err = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
 
-        if (IS_ERR(p) || cpu_online(cpu)) {
+        if (err || cpu_online(cpu)) {
                 /* CPU didn't die: tell everyone.  Can't complain. */
                 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
                                             hcpu) == NOTIFY_BAD)
                         BUG();
 
-                if (IS_ERR(p)) {
-                        err = PTR_ERR(p);
-                        goto out_allowed;
-                }
-                goto out_thread;
+                goto out_allowed;
         }
 
         /* Wait for it to sleep (leaving idle task). */
@@ -279,8 +274,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 
         check_for_tasks(cpu);
 
-out_thread:
-        err = kthread_stop(p);
 out_allowed:
         set_cpus_allowed_ptr(current, &old_allowed);
 out_release: