[20/28] threadpool: add thread_pool_new() and thread_pool_free()

diff --git a/include/block/thread-pool.h b/include/block/thread-pool.h
index 200703e..e1453c6 100644
--- a/include/block/thread-pool.h
+++ b/include/block/thread-pool.h
@@ -26,6 +26,11 @@ 
 
 typedef int ThreadPoolFunc(void *opaque);
 
+typedef struct ThreadPool ThreadPool;
+
+ThreadPool *thread_pool_new(struct AioContext *ctx);
+void thread_pool_free(ThreadPool *pool);
+
 BlockDriverAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg,
      BlockDriverCompletionFunc *cb, void *opaque);
 int coroutine_fn thread_pool_submit_co(ThreadPoolFunc *func, void *arg);
diff --git a/thread-pool.c b/thread-pool.c
index a0aecd0..d1e4570 100644
--- a/thread-pool.c
+++ b/thread-pool.c
@@ -24,8 +24,6 @@ 
 #include "qemu/event_notifier.h"
 #include "block/thread-pool.h"
 
-typedef struct ThreadPool ThreadPool;
-
 static void do_spawn_thread(ThreadPool *pool);
 
 typedef struct ThreadPoolElement ThreadPoolElement;
@@ -59,8 +57,10 @@  struct ThreadPoolElement {
 
 struct ThreadPool {
     EventNotifier notifier;
+    AioContext *ctx;
     QemuMutex lock;
     QemuCond check_cancel;
+    QemuCond worker_stopped;
     QemuSemaphore sem;
     int max_threads;
     QEMUBH *new_thread_bh;
@@ -75,6 +75,7 @@  struct ThreadPool {
     int new_threads;     /* backlog of threads we need to create */
     int pending_threads; /* threads created but not running yet */
     int pending_cancellations; /* whether we need a cond_broadcast */
+    bool stopping;
 };
 
 /* Currently there is only one thread pool instance. */
@@ -88,7 +89,7 @@  static void *worker_thread(void *opaque)
     pool->pending_threads--;
     do_spawn_thread(pool);
 
-    while (1) {
+    while (!pool->stopping) {
         ThreadPoolElement *req;
         int ret;
 
@@ -99,7 +100,7 @@  static void *worker_thread(void *opaque)
             qemu_mutex_lock(&pool->lock);
             pool->idle_threads--;
         } while (ret == -1 && !QTAILQ_EMPTY(&pool->request_list));
-        if (ret == -1) {
+        if (ret == -1 || pool->stopping) {
             break;
         }
 
@@ -124,6 +125,7 @@  static void *worker_thread(void *opaque)
     }
 
     pool->cur_threads--;
+    qemu_cond_signal(&pool->worker_stopped);
     qemu_mutex_unlock(&pool->lock);
     return NULL;
 }
@@ -298,8 +300,10 @@  static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
 
     memset(pool, 0, sizeof(*pool));
     event_notifier_init(&pool->notifier, false);
+    pool->ctx = ctx;
     qemu_mutex_init(&pool->lock);
     qemu_cond_init(&pool->check_cancel);
+    qemu_cond_init(&pool->worker_stopped);
     qemu_sem_init(&pool->sem, 0);
     pool->max_threads = 64;
     pool->new_thread_bh = aio_bh_new(ctx, spawn_thread_bh_fn, pool);
@@ -311,6 +315,46 @@  static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
                            thread_pool_active);
 }
 
+ThreadPool *thread_pool_new(AioContext *ctx)
+{
+    ThreadPool *pool = g_new(ThreadPool, 1);
+    thread_pool_init_one(pool, ctx);
+    return pool;
+}
+
+void thread_pool_free(ThreadPool *pool)
+{
+    if (!pool) {
+        return;
+    }
+
+    assert(QLIST_EMPTY(&pool->head));
+
+    qemu_mutex_lock(&pool->lock);
+
+    /* Stop new threads from spawning */
+    qemu_bh_delete(pool->new_thread_bh);
+    pool->cur_threads -= pool->new_threads;
+    pool->new_threads = 0;
+
+    /* Wait for worker threads to terminate */
+    pool->stopping = true;
+    while (pool->cur_threads > 0) {
+        qemu_sem_post(&pool->sem);
+        qemu_cond_wait(&pool->worker_stopped, &pool->lock);
+    }
+
+    qemu_mutex_unlock(&pool->lock);
+
+    aio_set_event_notifier(pool->ctx, &pool->notifier, NULL, NULL);
+    qemu_sem_destroy(&pool->sem);
+    qemu_cond_destroy(&pool->check_cancel);
+    qemu_cond_destroy(&pool->worker_stopped);
+    qemu_mutex_destroy(&pool->lock);
+    event_notifier_cleanup(&pool->notifier);
+    g_free(pool);
+}
+
 static void thread_pool_init(void)
 {
     thread_pool_init_one(&global_pool, NULL);