workqueue: introduce cpu_singlethread_map

The code like

	if (is_single_threaded(wq))
		do_something(singlethread_cpu);
	else {
		for_each_cpu_mask(cpu, cpu_populated_map)
			do_something(cpu);
	}

looks very annoying. We can add "static cpumask_t cpu_singlethread_map" and
simplify the code. Lessens .text a bit, and imho makes the code more readable.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 30 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index ce72d45c7f..6308a4bc6a 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -69,6 +69,7 @@ static DEFINE_MUTEX(workqueue_mutex);
 static LIST_HEAD(workqueues);
 
 static int singlethread_cpu __read_mostly;
+static cpumask_t cpu_singlethread_map __read_mostly;
 /* optimization, we could use cpu_possible_map */
 static cpumask_t cpu_populated_map __read_mostly;
 
@@ -78,6 +79,12 @@ static inline int is_single_threaded(struct workqueue_struct *wq)
         return list_empty(&wq->list);
 }
 
+static const cpumask_t *wq_cpu_map(struct workqueue_struct *wq)
+{
+        return is_single_threaded(wq)
+                ? &cpu_singlethread_map : &cpu_populated_map;
+}
+
 /*
  * Set the workqueue on which a work item is to be run
  * - Must *only* be called if the pending flag is set
@@ -393,16 +400,12 @@ static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
  */
 void fastcall flush_workqueue(struct workqueue_struct *wq)
 {
-        might_sleep();
-
-        if (is_single_threaded(wq))
-                flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, singlethread_cpu));
-        else {
-                int cpu;
+        const cpumask_t *cpu_map = wq_cpu_map(wq);
+        int cpu
 
-                for_each_cpu_mask(cpu, cpu_populated_map)
-                        flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
-        }
+        might_sleep();
+        for_each_cpu_mask(cpu, *cpu_map)
+                flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));
 }
 EXPORT_SYMBOL_GPL(flush_workqueue);
 
@@ -439,7 +442,9 @@ static void wait_on_work(struct cpu_workqueue_struct *cwq,
  */
 void flush_work(struct workqueue_struct *wq, struct work_struct *work)
 {
+        const cpumask_t *cpu_map = wq_cpu_map(wq);
         struct cpu_workqueue_struct *cwq;
+        int cpu;
 
         might_sleep();
 
@@ -457,14 +462,8 @@ void flush_work(struct workqueue_struct *wq, struct work_struct *work)
         work_release(work);
         spin_unlock_irq(&cwq->lock);
 
-        if (is_single_threaded(wq))
-                wait_on_work(per_cpu_ptr(wq->cpu_wq, singlethread_cpu), work);
-        else {
-                int cpu;
-
-                for_each_cpu_mask(cpu, cpu_populated_map)
-                        wait_on_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
-        }
+        for_each_cpu_mask(cpu, *cpu_map)
+                wait_on_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
 }
 EXPORT_SYMBOL_GPL(flush_work);
 
@@ -757,22 +756,17 @@ static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
  */
 void destroy_workqueue(struct workqueue_struct *wq)
 {
+        const cpumask_t *cpu_map = wq_cpu_map(wq);
         struct cpu_workqueue_struct *cwq;
+        int cpu;
 
-        if (is_single_threaded(wq)) {
-                cwq = per_cpu_ptr(wq->cpu_wq, singlethread_cpu);
-                cleanup_workqueue_thread(cwq, singlethread_cpu);
-        } else {
-                int cpu;
+        mutex_lock(&workqueue_mutex);
+        list_del(&wq->list);
+        mutex_unlock(&workqueue_mutex);
 
-                mutex_lock(&workqueue_mutex);
-                list_del(&wq->list);
-                mutex_unlock(&workqueue_mutex);
-
-                for_each_cpu_mask(cpu, cpu_populated_map) {
-                        cwq = per_cpu_ptr(wq->cpu_wq, cpu);
-                        cleanup_workqueue_thread(cwq, cpu);
-                }
+        for_each_cpu_mask(cpu, *cpu_map) {
+                cwq = per_cpu_ptr(wq->cpu_wq, cpu);
+                cleanup_workqueue_thread(cwq, cpu);
         }
 
         free_percpu(wq->cpu_wq);
@@ -831,6 +825,7 @@ void init_workqueues(void)
 {
         cpu_populated_map = cpu_online_map;
         singlethread_cpu = first_cpu(cpu_possible_map);
+        cpu_singlethread_map = cpumask_of_cpu(singlethread_cpu);
         hotcpu_notifier(workqueue_cpu_callback, 0);
         keventd_wq = create_workqueue("events");
         BUG_ON(!keventd_wq);