threadpool: drop global thread pool

Now that each AioContext has a ThreadPool and the main loop AioContext
can be fetched with bdrv_get_aio_context(), we can eliminate the concept
of a global thread pool from thread-pool.c.

The submit functions must take a ThreadPool* argument.

block/raw-posix.c and block/raw-win32.c use
aio_get_thread_pool(bdrv_get_aio_context(bs)) to fetch the main loop's
ThreadPool.

tests/test-thread-pool.c must be updated to reflect the new
thread_pool_submit() function prototypes.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

block/raw-posix.c

@@ -750,6 +750,7 @@ static BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
         BlockDriverCompletionFunc *cb, void *opaque, int type)
 {
     RawPosixAIOData *acb = g_slice_new(RawPosixAIOData);
+    ThreadPool *pool;
 
     acb->bs = bs;
     acb->aio_type = type;
@@ -763,7 +764,8 @@ static BlockDriverAIOCB *paio_submit(BlockDriverState *bs, int fd,
     acb->aio_offset = sector_num * 512;
 
     trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
-    return thread_pool_submit_aio(aio_worker, acb, cb, opaque);
+    pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
+    return thread_pool_submit_aio(pool, aio_worker, acb, cb, opaque);
 }
 
 static BlockDriverAIOCB *raw_aio_submit(BlockDriverState *bs,
@@ -1413,6 +1415,7 @@ static BlockDriverAIOCB *hdev_aio_ioctl(BlockDriverState *bs,
 {
     BDRVRawState *s = bs->opaque;
     RawPosixAIOData *acb;
+    ThreadPool *pool;
 
     if (fd_open(bs) < 0)
         return NULL;
@@ -1424,7 +1427,8 @@ static BlockDriverAIOCB *hdev_aio_ioctl(BlockDriverState *bs,
     acb->aio_offset = 0;
     acb->aio_ioctl_buf = buf;
     acb->aio_ioctl_cmd = req;
-    return thread_pool_submit_aio(aio_worker, acb, cb, opaque);
+    pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
+    return thread_pool_submit_aio(pool, aio_worker, acb, cb, opaque);
 }
 
 #elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__)

block/raw-win32.c

@@ -144,6 +144,7 @@ static BlockDriverAIOCB *paio_submit(BlockDriverState *bs, HANDLE hfile,
         BlockDriverCompletionFunc *cb, void *opaque, int type)
 {
     RawWin32AIOData *acb = g_slice_new(RawWin32AIOData);
+    ThreadPool *pool;
 
     acb->bs = bs;
     acb->hfile = hfile;
@@ -157,7 +158,8 @@ static BlockDriverAIOCB *paio_submit(BlockDriverState *bs, HANDLE hfile,
     acb->aio_offset = sector_num * 512;
 
     trace_paio_submit(acb, opaque, sector_num, nb_sectors, type);
-    return thread_pool_submit_aio(aio_worker, acb, cb, opaque);
+    pool = aio_get_thread_pool(bdrv_get_aio_context(bs));
+    return thread_pool_submit_aio(pool, aio_worker, acb, cb, opaque);
 }
 
 int qemu_ftruncate64(int fd, int64_t length)

include/block/thread-pool.h

@@ -31,9 +31,11 @@ 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,
+BlockDriverAIOCB *thread_pool_submit_aio(ThreadPool *pool,
-     BlockDriverCompletionFunc *cb, void *opaque);
+        ThreadPoolFunc *func, void *arg,
-int coroutine_fn thread_pool_submit_co(ThreadPoolFunc *func, void *arg);
+        BlockDriverCompletionFunc *cb, void *opaque);
-void thread_pool_submit(ThreadPoolFunc *func, void *arg);
+int coroutine_fn thread_pool_submit_co(ThreadPool *pool,
+        ThreadPoolFunc *func, void *arg);
+void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, void *arg);
 
 #endif

tests/test-thread-pool.c

@@ -4,6 +4,8 @@
 #include "block/thread-pool.h"
 #include "block/block.h"
 
+static AioContext *ctx;
+static ThreadPool *pool;
 static int active;
 
 typedef struct {
@@ -38,19 +40,10 @@ static void done_cb(void *opaque, int ret)
     active--;
 }
 
-/* A non-blocking poll of the main AIO context (we cannot use aio_poll
- * because we do not know the AioContext).
- */
-static void qemu_aio_wait_nonblocking(void)
-{
-    qemu_notify_event();
-    qemu_aio_wait();
-}
-
 /* Wait until all aio and bh activity has finished */
 static void qemu_aio_wait_all(void)
 {
-    while (qemu_aio_wait()) {
+    while (aio_poll(ctx, true)) {
         /* Do nothing */
     }
 }
@@ -58,7 +51,7 @@ static void qemu_aio_wait_all(void)
 static void test_submit(void)
 {
     WorkerTestData data = { .n = 0 };
-    thread_pool_submit(worker_cb, &data);
+    thread_pool_submit(pool, worker_cb, &data);
     qemu_aio_wait_all();
     g_assert_cmpint(data.n, ==, 1);
 }
@@ -66,7 +59,8 @@ static void test_submit(void)
 static void test_submit_aio(void)
 {
     WorkerTestData data = { .n = 0, .ret = -EINPROGRESS };
-    data.aiocb = thread_pool_submit_aio(worker_cb, &data, done_cb, &data);
+    data.aiocb = thread_pool_submit_aio(pool, worker_cb, &data,
+                                        done_cb, &data);
 
     /* The callbacks are not called until after the first wait.  */
     active = 1;
@@ -84,7 +78,7 @@ static void co_test_cb(void *opaque)
     active = 1;
     data->n = 0;
     data->ret = -EINPROGRESS;
-    thread_pool_submit_co(worker_cb, data);
+    thread_pool_submit_co(pool, worker_cb, data);
 
     /* The test continues in test_submit_co, after qemu_coroutine_enter... */
 
@@ -126,12 +120,12 @@ static void test_submit_many(void)
     for (i = 0; i < 100; i++) {
         data[i].n = 0;
         data[i].ret = -EINPROGRESS;
-        thread_pool_submit_aio(worker_cb, &data[i], done_cb, &data[i]);
+        thread_pool_submit_aio(pool, worker_cb, &data[i], done_cb, &data[i]);
     }
 
     active = 100;
     while (active > 0) {
-        qemu_aio_wait();
+        aio_poll(ctx, true);
     }
     for (i = 0; i < 100; i++) {
         g_assert_cmpint(data[i].n, ==, 1);
@@ -154,7 +148,7 @@ static void test_cancel(void)
     for (i = 0; i < 100; i++) {
         data[i].n = 0;
         data[i].ret = -EINPROGRESS;
-        data[i].aiocb = thread_pool_submit_aio(long_cb, &data[i],
+        data[i].aiocb = thread_pool_submit_aio(pool, long_cb, &data[i],
                                                done_cb, &data[i]);
     }
 
@@ -162,7 +156,8 @@ static void test_cancel(void)
      * run, but do not waste too much time...
      */
     active = 100;
-    qemu_aio_wait_nonblocking();
+    aio_notify(ctx);
+    aio_poll(ctx, false);
 
     /* Wait some time for the threads to start, with some sanity
      * testing on the behavior of the scheduler...
@@ -208,11 +203,10 @@ static void test_cancel(void)
 
 int main(int argc, char **argv)
 {
-    /* These should be removed once each AioContext has its thread pool.
+    int ret;
-     * The test should create its own AioContext.
+
-     */
+    ctx = aio_context_new();
-    qemu_init_main_loop();
+    pool = aio_get_thread_pool(ctx);
-    bdrv_init();
 
     g_test_init(&argc, &argv, NULL);
     g_test_add_func("/thread-pool/submit", test_submit);
@@ -220,5 +214,9 @@ int main(int argc, char **argv)
     g_test_add_func("/thread-pool/submit-co", test_submit_co);
     g_test_add_func("/thread-pool/submit-many", test_submit_many);
     g_test_add_func("/thread-pool/cancel", test_cancel);
-    return g_test_run();
+
+    ret = g_test_run();
+
+    aio_context_unref(ctx);
+    return ret;
 }

thread-pool.c

@@ -78,9 +78,6 @@ struct ThreadPool {
     bool stopping;
 };
 
-/* Currently there is only one thread pool instance. */
-static ThreadPool global_pool;
-
 static void *worker_thread(void *opaque)
 {
     ThreadPool *pool = opaque;
@@ -239,10 +236,10 @@ static const AIOCBInfo thread_pool_aiocb_info = {
     .cancel             = thread_pool_cancel,
 };
 
-BlockDriverAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg,
+BlockDriverAIOCB *thread_pool_submit_aio(ThreadPool *pool,
+        ThreadPoolFunc *func, void *arg,
         BlockDriverCompletionFunc *cb, void *opaque)
 {
-    ThreadPool *pool = &global_pool;
     ThreadPoolElement *req;
 
     req = qemu_aio_get(&thread_pool_aiocb_info, NULL, cb, opaque);
@@ -278,18 +275,19 @@ static void thread_pool_co_cb(void *opaque, int ret)
     qemu_coroutine_enter(co->co, NULL);
 }
 
-int coroutine_fn thread_pool_submit_co(ThreadPoolFunc *func, void *arg)
+int coroutine_fn thread_pool_submit_co(ThreadPool *pool, ThreadPoolFunc *func,
+                                       void *arg)
 {
     ThreadPoolCo tpc = { .co = qemu_coroutine_self(), .ret = -EINPROGRESS };
     assert(qemu_in_coroutine());
-    thread_pool_submit_aio(func, arg, thread_pool_co_cb, &tpc);
+    thread_pool_submit_aio(pool, func, arg, thread_pool_co_cb, &tpc);
     qemu_coroutine_yield();
     return tpc.ret;
 }
 
-void thread_pool_submit(ThreadPoolFunc *func, void *arg)
+void thread_pool_submit(ThreadPool *pool, ThreadPoolFunc *func, void *arg)
 {
-    thread_pool_submit_aio(func, arg, NULL, NULL);
+    thread_pool_submit_aio(pool, func, arg, NULL, NULL);
 }
 
 static void thread_pool_init_one(ThreadPool *pool, AioContext *ctx)
@@ -354,10 +352,3 @@ void thread_pool_free(ThreadPool *pool)
     event_notifier_cleanup(&pool->notifier);
     g_free(pool);
 }
-
-static void thread_pool_init(void)
-{
-    thread_pool_init_one(&global_pool, NULL);
-}
-
-block_init(thread_pool_init)