[PATCH 2/6] block/aio_task: allow start/wait task from any coroutine

["Denis V. Lunev" <den@openvz.org>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Currently, aio task pool assumes that there is a main coroutine, which
creates tasks and wait for them. Let's remove the restriction by using
CoQueue. Code becomes clearer, interface more obvious.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Fam Zheng <fam@euphon.net>
CC: Juan Quintela <quintela@redhat.com>
CC: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
CC: Denis Plotnikov <dplotnikov@virtuozzo.com>
---
 block/aio_task.c | 21 ++++++---------------
 1 file changed, 6 insertions(+), 15 deletions(-)

diff --git a/block/aio_task.c b/block/aio_task.c
index 88989fa248..cf62e5c58b 100644
--- a/block/aio_task.c
+++ b/block/aio_task.c
@@ -27,11 +27,10 @@
 #include "block/aio_task.h"
 
 struct AioTaskPool {
-    Coroutine *main_co;
     int status;
     int max_busy_tasks;
     int busy_tasks;
-    bool waiting;
+    CoQueue waiters;
 };
 
 static void coroutine_fn aio_task_co(void *opaque)
@@ -52,31 +51,23 @@ static void coroutine_fn aio_task_co(void *opaque)
 
     g_free(task);
 
-    if (pool->waiting) {
-        pool->waiting = false;
-        aio_co_wake(pool->main_co);
-    }
+    qemu_co_queue_restart_all(&pool->waiters);
 }
 
 void coroutine_fn aio_task_pool_wait_one(AioTaskPool *pool)
 {
     assert(pool->busy_tasks > 0);
-    assert(qemu_coroutine_self() == pool->main_co);
 
-    pool->waiting = true;
-    qemu_coroutine_yield();
+    qemu_co_queue_wait(&pool->waiters, NULL);
 
-    assert(!pool->waiting);
     assert(pool->busy_tasks < pool->max_busy_tasks);
 }
 
 void coroutine_fn aio_task_pool_wait_slot(AioTaskPool *pool)
 {
-    if (pool->busy_tasks < pool->max_busy_tasks) {
-        return;
+    while (pool->busy_tasks >= pool->max_busy_tasks) {
+        aio_task_pool_wait_one(pool);
     }
-
-    aio_task_pool_wait_one(pool);
 }
 
 void coroutine_fn aio_task_pool_wait_all(AioTaskPool *pool)
@@ -98,8 +89,8 @@ AioTaskPool *coroutine_fn aio_task_pool_new(int max_busy_tasks)
 {
     AioTaskPool *pool = g_new0(AioTaskPool, 1);
 
-    pool->main_co = qemu_coroutine_self();
     pool->max_busy_tasks = max_busy_tasks;
+    qemu_co_queue_init(&pool->waiters);
 
     return pool;
 }
-- 
2.17.1