coroutine: use QSIMPLEQ instead of QTAILQ

CoQueue do not need to remove any element but the head of the list;
processing is always strictly FIFO.  Therefore, the simpler singly-linked
QSIMPLEQ can be used instead.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

include/qemu/coroutine.h

@@ -102,7 +102,7 @@ bool qemu_in_coroutine(void);
  * are built.
  */
 typedef struct CoQueue {
-    QTAILQ_HEAD(, Coroutine) entries;
+    QSIMPLEQ_HEAD(, Coroutine) entries;
 } CoQueue;
 
 /**

include/qemu/coroutine_int.h

@@ -41,8 +41,8 @@ struct Coroutine {
     QSLIST_ENTRY(Coroutine) pool_next;
 
     /* Coroutines that should be woken up when we yield or terminate */
-    QTAILQ_HEAD(, Coroutine) co_queue_wakeup;
-    QTAILQ_ENTRY(Coroutine) co_queue_next;
+    QSIMPLEQ_HEAD(, Coroutine) co_queue_wakeup;
+    QSIMPLEQ_ENTRY(Coroutine) co_queue_next;
 };
 
 Coroutine *qemu_coroutine_new(void);

util/qemu-coroutine-lock.c

@@ -31,13 +31,13 @@
 
 void qemu_co_queue_init(CoQueue *queue)
 {
-    QTAILQ_INIT(&queue->entries);
+    QSIMPLEQ_INIT(&queue->entries);
 }
 
 void coroutine_fn qemu_co_queue_wait(CoQueue *queue)
 {
     Coroutine *self = qemu_coroutine_self();
-    QTAILQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
+    QSIMPLEQ_INSERT_TAIL(&queue->entries, self, co_queue_next);
     qemu_coroutine_yield();
     assert(qemu_in_coroutine());
 }
@@ -55,8 +55,8 @@ void qemu_co_queue_run_restart(Coroutine *co)
     Coroutine *next;
 
     trace_qemu_co_queue_run_restart(co);
-    while ((next = QTAILQ_FIRST(&co->co_queue_wakeup))) {
-        QTAILQ_REMOVE(&co->co_queue_wakeup, next, co_queue_next);
+    while ((next = QSIMPLEQ_FIRST(&co->co_queue_wakeup))) {
+        QSIMPLEQ_REMOVE_HEAD(&co->co_queue_wakeup, co_queue_next);
         qemu_coroutine_enter(next, NULL);
     }
 }
@@ -66,13 +66,13 @@ static bool qemu_co_queue_do_restart(CoQueue *queue, bool single)
     Coroutine *self = qemu_coroutine_self();
     Coroutine *next;
 
-    if (QTAILQ_EMPTY(&queue->entries)) {
+    if (QSIMPLEQ_EMPTY(&queue->entries)) {
         return false;
     }
 
-    while ((next = QTAILQ_FIRST(&queue->entries)) != NULL) {
-        QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
-        QTAILQ_INSERT_TAIL(&self->co_queue_wakeup, next, co_queue_next);
+    while ((next = QSIMPLEQ_FIRST(&queue->entries)) != NULL) {
+        QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
+        QSIMPLEQ_INSERT_TAIL(&self->co_queue_wakeup, next, co_queue_next);
         trace_qemu_co_queue_next(next);
         if (single) {
             break;
@@ -97,19 +97,19 @@ bool qemu_co_enter_next(CoQueue *queue)
 {
     Coroutine *next;
 
-    next = QTAILQ_FIRST(&queue->entries);
+    next = QSIMPLEQ_FIRST(&queue->entries);
     if (!next) {
         return false;
     }
 
-    QTAILQ_REMOVE(&queue->entries, next, co_queue_next);
+    QSIMPLEQ_REMOVE_HEAD(&queue->entries, co_queue_next);
     qemu_coroutine_enter(next, NULL);
     return true;
 }
 
 bool qemu_co_queue_empty(CoQueue *queue)
 {
-    return QTAILQ_FIRST(&queue->entries) == NULL;
+    return QSIMPLEQ_FIRST(&queue->entries) == NULL;
 }
 
 void qemu_co_mutex_init(CoMutex *mutex)

util/qemu-coroutine.c

@@ -76,7 +76,7 @@ Coroutine *qemu_coroutine_create(CoroutineEntry *entry)
     }
 
     co->entry = entry;
-    QTAILQ_INIT(&co->co_queue_wakeup);
+    QSIMPLEQ_INIT(&co->co_queue_wakeup);
     return co;
 }