async: use workqueue for worker pool

Replace private worker pool with system_unbound_wq.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Arjan van de Ven <arjan@infradead.org>

1 files changed, 22 insertions, 119 deletions

diff --git a/kernel/async.c b/kernel/async.c
index 15319d6c18fe..cd9dbb913c77 100644
--- a/kernel/async.c
+++ b/kernel/async.c
@@ -49,40 +49,33 @@ asynchronous and synchronous parts of the kernel.
 */
 
 #include <linux/async.h>
-#include <linux/bug.h>
 #include <linux/module.h>
 #include <linux/wait.h>
 #include <linux/sched.h>
-#include <linux/init.h>
-#include <linux/kthread.h>
-#include <linux/delay.h>
 #include <linux/slab.h>
+#include <linux/workqueue.h>
 #include <asm/atomic.h>
 
 static async_cookie_t next_cookie = 1;
 
-#define MAX_THREADS     256
 #define MAX_WORK        32768
 
 static LIST_HEAD(async_pending);
 static LIST_HEAD(async_running);
 static DEFINE_SPINLOCK(async_lock);
 
-static int async_enabled = 0;
-
 struct async_entry {
-        struct list_head list;
-        async_cookie_t   cookie;
-        async_func_ptr   *func;
-        void             *data;
-        struct list_head *running;
+        struct list_head        list;
+        struct work_struct      work;
+        async_cookie_t          cookie;
+        async_func_ptr          *func;
+        void                    *data;
+        struct list_head        *running;
 };
 
 static DECLARE_WAIT_QUEUE_HEAD(async_done);
-static DECLARE_WAIT_QUEUE_HEAD(async_new);
 
 static atomic_t entry_count;
-static atomic_t thread_count;
 
 extern int initcall_debug;
 
@@ -117,27 +110,23 @@ static async_cookie_t  lowest_in_progress(struct list_head *running)
         spin_unlock_irqrestore(&async_lock, flags);
         return ret;
 }
+
 /*
  * pick the first pending entry and run it
  */
-static void run_one_entry(void)
+static void async_run_entry_fn(struct work_struct *work)
 {
+        struct async_entry *entry =
+                container_of(work, struct async_entry, work);
         unsigned long flags;
-        struct async_entry *entry;
         ktime_t calltime, delta, rettime;
 
-        /* 1) pick one task from the pending queue */
-
+        /* 1) move self to the running queue */
         spin_lock_irqsave(&async_lock, flags);
-        if (list_empty(&async_pending))
-                goto out;
-        entry = list_first_entry(&async_pending, struct async_entry, list);
-
-        /* 2) move it to the running queue */
         list_move_tail(&entry->list, entry->running);
         spin_unlock_irqrestore(&async_lock, flags);
 
-        /* 3) run it (and print duration)*/
+        /* 2) run (and print duration) */
         if (initcall_debug && system_state == SYSTEM_BOOTING) {
                 printk("calling  %lli_%pF @ %i\n", (long long)entry->cookie,
                         entry->func, task_pid_nr(current));
@@ -153,31 +142,25 @@ static void run_one_entry(void)
                         (long long)ktime_to_ns(delta) >> 10);
         }
 
-        /* 4) remove it from the running queue */
+        /* 3) remove self from the running queue */
         spin_lock_irqsave(&async_lock, flags);
         list_del(&entry->list);
 
-        /* 5) free the entry  */
+        /* 4) free the entry */
         kfree(entry);
         atomic_dec(&entry_count);
 
         spin_unlock_irqrestore(&async_lock, flags);
 
-        /* 6) wake up any waiters. */
+        /* 5) wake up any waiters */
         wake_up(&async_done);
-        return;
-
-out:
-        spin_unlock_irqrestore(&async_lock, flags);
 }
 
-
 static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct list_head *running)
 {
         struct async_entry *entry;
         unsigned long flags;
         async_cookie_t newcookie;
-        
 
         /* allow irq-off callers */
         entry = kzalloc(sizeof(struct async_entry), GFP_ATOMIC);
@@ -186,7 +169,7 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct l
          * If we're out of memory or if there's too much work
          * pending already, we execute synchronously.
          */
-        if (!async_enabled || !entry || atomic_read(&entry_count) > MAX_WORK) {
+        if (!entry || atomic_read(&entry_count) > MAX_WORK) {
                 kfree(entry);
                 spin_lock_irqsave(&async_lock, flags);
                 newcookie = next_cookie++;
@@ -196,6 +179,7 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct l
                 ptr(data, newcookie);
                 return newcookie;
         }
+        INIT_WORK(&entry->work, async_run_entry_fn);
         entry->func = ptr;
         entry->data = data;
         entry->running = running;
@@ -205,7 +189,10 @@ static async_cookie_t __async_schedule(async_func_ptr *ptr, void *data, struct l
         list_add_tail(&entry->list, &async_pending);
         atomic_inc(&entry_count);
         spin_unlock_irqrestore(&async_lock, flags);
-        wake_up(&async_new);
+
+        /* schedule for execution */
+        queue_work(system_unbound_wq, &entry->work);
+
         return newcookie;
 }
 
@@ -312,87 +299,3 @@ void async_synchronize_cookie(async_cookie_t cookie)
         async_synchronize_cookie_domain(cookie, &async_running);
 }
 EXPORT_SYMBOL_GPL(async_synchronize_cookie);
-
-
-static int async_thread(void *unused)
-{
-        DECLARE_WAITQUEUE(wq, current);
-        add_wait_queue(&async_new, &wq);
-
-        while (!kthread_should_stop()) {
-                int ret = HZ;
-                set_current_state(TASK_INTERRUPTIBLE);
-                /*
-                 * check the list head without lock.. false positives
-                 * are dealt with inside run_one_entry() while holding
-                 * the lock.
-                 */
-                rmb();
-                if (!list_empty(&async_pending))
-                        run_one_entry();
-                else
-                        ret = schedule_timeout(HZ);
-
-                if (ret == 0) {
-                        /*
-                         * we timed out, this means we as thread are redundant.
-                         * we sign off and die, but we to avoid any races there
-                         * is a last-straw check to see if work snuck in.
-                         */
-                        atomic_dec(&thread_count);
-                        wmb(); /* manager must see our departure first */
-                        if (list_empty(&async_pending))
-                                break;
-                        /*
-                         * woops work came in between us timing out and us
-                         * signing off; we need to stay alive and keep working.
-                         */
-                        atomic_inc(&thread_count);
-                }
-        }
-        remove_wait_queue(&async_new, &wq);
-
-        return 0;
-}
-
-static int async_manager_thread(void *unused)
-{
-        DECLARE_WAITQUEUE(wq, current);
-        add_wait_queue(&async_new, &wq);
-
-        while (!kthread_should_stop()) {
-                int tc, ec;
-
-                set_current_state(TASK_INTERRUPTIBLE);
-
-                tc = atomic_read(&thread_count);
-                rmb();
-                ec = atomic_read(&entry_count);
-
-                while (tc < ec && tc < MAX_THREADS) {
-                        if (IS_ERR(kthread_run(async_thread, NULL, "async/%i",
-                                               tc))) {
-                                msleep(100);
-                                continue;
-                        }
-                        atomic_inc(&thread_count);
-                        tc++;
-                }
-
-                schedule();
-        }
-        remove_wait_queue(&async_new, &wq);
-
-        return 0;
-}
-
-static int __init async_init(void)
-{
-        async_enabled =
-                !IS_ERR(kthread_run(async_manager_thread, NULL, "async/mgr"));
-
-        WARN_ON(!async_enabled);
-        return 0;
-}
-
-core_initcall(async_init);