[Qemu-devel] [PATCH] qemu-coroutine: Add simple work queue support

[Peter A. G. Crosthwaite]

Add a function co_queue_yield_to_next() which will immediately transfer
control to the coroutine at the head of a co queue. This can be used for
implementing simple work queues where the manager of a co-queue only
needs to restart queued routines one at a time.

Signed-off-by: Peter A. G. Crosthwaite <address@hidden>
---
 qemu-coroutine-lock.c |   13 +++++++++++++
 qemu-coroutine.h      |    9 +++++++++
 2 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/qemu-coroutine-lock.c b/qemu-coroutine-lock.c
index a80f437..de2fc21 100644
--- a/qemu-coroutine-lock.c
+++ b/qemu-coroutine-lock.c
@@ -75,6 +75,19 @@ bool qemu_co_queue_next(CoQueue *queue)
     return (next != NULL);
 }
 
+bool qemu_co_queue_yield_to_next(CoQueue *queue)
+{
+    Coroutine *next;
+
+    next = QTAILQ_FIRST(&queue->entries);
+    if (next) {
+        QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
+        qemu_coroutine_enter(next, NULL);
+    }
+
+    return (next != NULL);
+}
+
 bool qemu_co_queue_empty(CoQueue *queue)
 {
     return (QTAILQ_FIRST(&queue->entries) == NULL);
diff --git a/qemu-coroutine.h b/qemu-coroutine.h
index 2f2fd95..dbc3610 100644
--- a/qemu-coroutine.h
+++ b/qemu-coroutine.h
@@ -125,6 +125,15 @@ void coroutine_fn qemu_co_queue_wait(CoQueue *queue);
 bool qemu_co_queue_next(CoQueue *queue);
 
 /**
+ * Transfers control to the next coroutine in the CoQueue and removes it from
+ * the queue.
+ *
+ * Returns true once after control transfers back to caller, or false
+ * immediately if the queue is empty.
+ */
+bool qemu_co_queue_yield_to_next(CoQueue *queue)
+
+/**
  * Checks if the CoQueue is empty.
  */
 bool qemu_co_queue_empty(CoQueue *queue);
-- 
1.7.3.2