[Qemu-devel] [PATCH v4 2/8] coroutine: add qemu_co_queue_restart_all()

[Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>]

It's common to wake up all waiting coroutines.  Introduce the
qemu_co_queue_restart_all() function to do this instead of looping over
qemu_co_queue_next() in every caller.

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 block/qcow2.c         |    2 +-
 qemu-coroutine-lock.c |   15 ++++++++-------
 qemu-coroutine.h      |    5 +++++
 3 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/block/qcow2.c b/block/qcow2.c
index eab35d1..195e1b1 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -514,7 +514,7 @@ static void run_dependent_requests(BDRVQcowState *s, QCowL2Meta *m)
     /* Restart all dependent requests */
     if (!qemu_co_queue_empty(&m->dependent_requests)) {
         qemu_co_mutex_unlock(&s->lock);
-        while(qemu_co_queue_next(&m->dependent_requests));
+        qemu_co_queue_restart_all(&m->dependent_requests);
         qemu_co_mutex_lock(&s->lock);
     }
 }
diff --git a/qemu-coroutine-lock.c b/qemu-coroutine-lock.c
index 9549c07..26ad76b 100644
--- a/qemu-coroutine-lock.c
+++ b/qemu-coroutine-lock.c
@@ -84,6 +84,13 @@ bool qemu_co_queue_next(CoQueue *queue)
     return (next != NULL);
 }
 
+void qemu_co_queue_restart_all(CoQueue *queue)
+{
+    while (qemu_co_queue_next(queue)) {
+        /* Do nothing */
+    }
+}
+
 bool qemu_co_queue_empty(CoQueue *queue)
 {
     return (QTAILQ_FIRST(&queue->entries) == NULL);
@@ -144,13 +151,7 @@ void qemu_co_rwlock_unlock(CoRwlock *lock)
     assert(qemu_in_coroutine());
     if (lock->writer) {
         lock->writer = false;
-        while (!qemu_co_queue_empty(&lock->queue)) {
-            /*
-             * Wakeup every body. This will include some
-             * writers too.
-             */
-            qemu_co_queue_next(&lock->queue);
-        }
+        qemu_co_queue_restart_all(&lock->queue);
     } else {
         lock->reader--;
         assert(lock->reader >= 0);
diff --git a/qemu-coroutine.h b/qemu-coroutine.h
index 8a2e5d2..8a55fe1 100644
--- a/qemu-coroutine.h
+++ b/qemu-coroutine.h
@@ -131,6 +131,11 @@ void coroutine_fn qemu_co_queue_wait_insert_head(CoQueue *queue);
 bool qemu_co_queue_next(CoQueue *queue);
 
 /**
+ * Restarts all coroutines in the CoQueue and leaves the queue empty.
+ */
+void qemu_co_queue_restart_all(CoQueue *queue);
+
+/**
  * Checks if the CoQueue is empty.
  */
 bool qemu_co_queue_empty(CoQueue *queue);
-- 
1.7.7.1