workqueue: destroy worker directly in the idle timeout handler

Since destroy_worker() doesn't need to sleep nor require manager_mutex,
destroy_worker() can be directly called in the idle timeout
handler, it helps us remove POOL_MANAGE_WORKERS and
maybe_destroy_worker() and simplify the manage_workers()

After POOL_MANAGE_WORKERS is removed, worker_thread() doesn't
need to test whether it needs to manage after processed works.
So we can remove the test branch.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>

1 files changed, 5 insertions, 62 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c458d73022bb..938836bc6207 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -68,7 +68,6 @@ enum {
          * manager_mutex to avoid changing binding state while
          * create_worker() is in progress.
          */
-        POOL_MANAGE_WORKERS     = 1 << 0,       /* need to manage workers */
         POOL_DISASSOCIATED      = 1 << 2,       /* cpu can't serve workers */
         POOL_FREEZING           = 1 << 3,       /* freeze in progress */
 
@@ -752,13 +751,6 @@ static bool need_to_create_worker(struct worker_pool *pool)
         return need_more_worker(pool) && !may_start_working(pool);
 }
 
-/* Do I need to be the manager? */
-static bool need_to_manage_workers(struct worker_pool *pool)
-{
-        return need_to_create_worker(pool) ||
-                (pool->flags & POOL_MANAGE_WORKERS);
-}
-
 /* Do we have too many workers and should some go away? */
 static bool too_many_workers(struct worker_pool *pool)
 {
@@ -1868,7 +1860,7 @@ static void idle_worker_timeout(unsigned long __pool)
 
         spin_lock_irq(&pool->lock);
 
-        if (too_many_workers(pool)) {
+        while (too_many_workers(pool)) {
                 struct worker *worker;
                 unsigned long expires;
 
@@ -1876,13 +1868,12 @@ static void idle_worker_timeout(unsigned long __pool)
                 worker = list_entry(pool->idle_list.prev, struct worker, entry);
                 expires = worker->last_active + IDLE_WORKER_TIMEOUT;
 
-                if (time_before(jiffies, expires))
+                if (time_before(jiffies, expires)) {
                         mod_timer(&pool->idle_timer, expires);
-                else {
-                        /* it's been idle for too long, wake up manager */
-                        pool->flags |= POOL_MANAGE_WORKERS;
-                        wake_up_worker(pool);
+                        break;
                 }
+
+                destroy_worker(worker);
         }
 
         spin_unlock_irq(&pool->lock);
@@ -2001,44 +1992,6 @@ restart:
 }
 
 /**
- * maybe_destroy_worker - destroy workers which have been idle for a while
- * @pool: pool to destroy workers for
- *
- * Destroy @pool workers which have been idle for longer than
- * IDLE_WORKER_TIMEOUT.
- *
- * LOCKING:
- * spin_lock_irq(pool->lock) which may be released and regrabbed
- * multiple times.  Called only from manager.
- *
- * Return:
- * %false if no action was taken and pool->lock stayed locked, %true
- * otherwise.
- */
-static bool maybe_destroy_workers(struct worker_pool *pool)
-{
-        bool ret = false;
-
-        while (too_many_workers(pool)) {
-                struct worker *worker;
-                unsigned long expires;
-
-                worker = list_entry(pool->idle_list.prev, struct worker, entry);
-                expires = worker->last_active + IDLE_WORKER_TIMEOUT;
-
-                if (time_before(jiffies, expires)) {
-                        mod_timer(&pool->idle_timer, expires);
-                        break;
-                }
-
-                destroy_worker(worker);
-                ret = true;
-        }
-
-        return ret;
-}
-
-/**
  * manage_workers - manage worker pool
  * @worker: self
  *
@@ -2101,13 +2054,6 @@ static bool manage_workers(struct worker *worker)
                 ret = true;
         }
 
-        pool->flags &= ~POOL_MANAGE_WORKERS;
-
-        /*
-         * Destroy and then create so that may_start_working() is true
-         * on return.
-         */
-        ret |= maybe_destroy_workers(pool);
         ret |= maybe_create_worker(pool);
 
         mutex_unlock(&pool->manager_mutex);
@@ -2349,9 +2295,6 @@ recheck:
 
         worker_set_flags(worker, WORKER_PREP, false);
 sleep:
-        if (unlikely(need_to_manage_workers(pool)) && manage_workers(worker))
-                goto recheck;
-
         /*
          * pool->lock is held and there's no work to process and no need to
          * manage, sleep.  Workers are woken up only while holding