The .cancel_async reuses the first half of .cancel: try to steal the
request if not submitted yet. In this case set the elem to a special
status THREAD_CANCELED_ASYNC, which means thread_pool_completion_bh
should call the cb with -ECANCELED.
If the request is already submitted, do nothing, as we know the normal
completion will happen in the future.
Signed-off-by: Fam Zheng <f...@redhat.com>
---
thread-pool.c | 44 +++++++++++++++++++++++++++++++++++---------
1 file changed, 35 insertions(+), 9 deletions(-)
diff --git a/thread-pool.c b/thread-pool.c
index 23888dc..9cb7a1d 100644
--- a/thread-pool.c
+++ b/thread-pool.c
@@ -202,6 +202,39 @@ restart:
}
}
+/* With elem->pool->lock held */
+static bool thread_pool_cancel_from_queue(ThreadPoolElement *elem)
+{
+ if (elem->state == THREAD_QUEUED &&
+ /* No thread has yet started working on elem. we can try to "steal"
+ * the item from the worker if we can get a signal from the
+ * semaphore. Because this is non-blocking, we can do it with
+ * the lock taken and ensure that elem will remain THREAD_QUEUED.
+ */
+ qemu_sem_timedwait(&elem->pool->sem, 0) == 0) {
+ QTAILQ_REMOVE(&elem->pool->request_list, elem, reqs);
+ qemu_bh_schedule(elem->pool->completion_bh);
+ return true;
+ }
+ return false;
+}
+
+static void thread_pool_cancel_async(BlockDriverAIOCB *acb)
+{
+ ThreadPoolElement *elem = (ThreadPoolElement *)acb;
+ ThreadPool *pool = elem->pool;
+
+ trace_thread_pool_cancel(elem, elem->common.opaque);
+
+ qemu_mutex_lock(&pool->lock);
+ if (thread_pool_cancel_from_queue(elem)) {
+ elem->state = THREAD_DONE;
+ elem->ret = -ECANCELED;
+ }
+
+ qemu_mutex_unlock(&pool->lock);
+}
+
static void thread_pool_cancel(BlockDriverAIOCB *acb)
{
ThreadPoolElement *elem = (ThreadPoolElement *)acb;
@@ -210,16 +243,8 @@ static void thread_pool_cancel(BlockDriverAIOCB *acb)
trace_thread_pool_cancel(elem, elem->common.opaque);
qemu_mutex_lock(&pool->lock);
- if (elem->state == THREAD_QUEUED &&
- /* No thread has yet started working on elem. we can try to "steal"
- * the item from the worker if we can get a signal from the
- * semaphore. Because this is non-blocking, we can do it with
- * the lock taken and ensure that elem will remain THREAD_QUEUED.
- */
- qemu_sem_timedwait(&pool->sem, 0) == 0) {
- QTAILQ_REMOVE(&pool->request_list, elem, reqs);
+ if (thread_pool_cancel_from_queue(elem)) {
elem->state = THREAD_CANCELED;
- qemu_bh_schedule(pool->completion_bh);
} else {
pool->pending_cancellations++;
while (elem->state != THREAD_CANCELED && elem->state != THREAD_DONE) {
@@ -234,6 +259,7 @@ static void thread_pool_cancel(BlockDriverAIOCB *acb)
static const AIOCBInfo thread_pool_aiocb_info = {
.aiocb_size = sizeof(ThreadPoolElement),
.cancel = thread_pool_cancel,
+ .cancel_async = thread_pool_cancel_async,
};
BlockDriverAIOCB *thread_pool_submit_aio(ThreadPool *pool,
--
2.1.0
