stop_machine: Introduce __cpu_stop_queue_work() and cpu_stop_queue_two_works()

Preparation to simplify the review of the next change. Add two simple
helpers, __cpu_stop_queue_work() and cpu_stop_queue_two_works() which
simply take a bit of code from their callers.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151008145134.GA18146@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 26 insertions, 11 deletions

diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index 6a402098d4ab..688d6b37bb59 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -73,21 +73,24 @@ static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed)
         }
 }
 
+static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
+                                        struct cpu_stop_work *work)
+{
+        list_add_tail(&work->list, &stopper->works);
+        wake_up_process(stopper->thread);
+}
+
 /* queue @work to @stopper.  if offline, @work is completed immediately */
 static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
 {
         struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
-
         unsigned long flags;
 
         spin_lock_irqsave(&stopper->lock, flags);
-
-        if (stopper->enabled) {
-                list_add_tail(&work->list, &stopper->works);
-                wake_up_process(stopper->thread);
-        } else
+        if (stopper->enabled)
+                __cpu_stop_queue_work(stopper, work);
+        else
                 cpu_stop_signal_done(work->done, false);
-
         spin_unlock_irqrestore(&stopper->lock, flags);
 }
 
@@ -213,6 +216,16 @@ static int multi_cpu_stop(void *data)
         return err;
 }
 
+static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
+                                    int cpu2, struct cpu_stop_work *work2)
+{
+        lg_double_lock(&stop_cpus_lock, cpu1, cpu2);
+        cpu_stop_queue_work(cpu1, work1);
+        cpu_stop_queue_work(cpu2, work2);
+        lg_double_unlock(&stop_cpus_lock, cpu1, cpu2);
+
+        return 0;
+}
 /**
  * stop_two_cpus - stops two cpus
  * @cpu1: the cpu to stop
@@ -260,10 +273,12 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
                 return -ENOENT;
         }
 
-        lg_double_lock(&stop_cpus_lock, cpu1, cpu2);
-        cpu_stop_queue_work(cpu1, &work1);
-        cpu_stop_queue_work(cpu2, &work2);
-        lg_double_unlock(&stop_cpus_lock, cpu1, cpu2);
+        if (cpu1 > cpu2)
+                swap(cpu1, cpu2);
+        if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) {
+                preempt_enable();
+                return -ENOENT;
+        }
 
         preempt_enable();