Because qemu_co_queue_restart_all does not release the lock, it should
be used only in coroutine context.  Introduce a new function that,
like qemu_co_enter_next, does release the lock, and use it whenever
qemu_co_queue_restart_all was used outside coroutine context.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/coroutine.h   | 13 +++++++++++++
 ui/console.c               |  2 +-
 util/qemu-coroutine-lock.c |  7 +++++++
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
index c23d41e1ff..e5954635f6 100644
--- a/include/qemu/coroutine.h
+++ b/include/qemu/coroutine.h
@@ -234,6 +234,19 @@ void qemu_co_queue_restart_all(CoQueue *queue);
     qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock))
 bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock);
 
+/**
+ * Empties the CoQueue, waking the waiting coroutine one at a time.  Unlike
+ * qemu_co_queue_all, this function releases the lock during aio_co_wake
+ * because it is meant to be used outside coroutine context; in that case, the
+ * coroutine is entered immediately, before qemu_co_enter_all returns.
+ *
+ * If used in coroutine context, qemu_co_enter_all is equivalent to
+ * qemu_co_queue_all.
+ */
+#define qemu_co_enter_all(queue, lock) \
+    qemu_co_enter_all_impl(queue, QEMU_MAKE_LOCKABLE(lock))
+void qemu_co_enter_all_impl(CoQueue *queue, QemuLockable *lock);
+
 /**
  * Checks if the CoQueue is empty.
  */
diff --git a/ui/console.c b/ui/console.c
index 1752f2ec88..afe3159394 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -218,7 +218,7 @@ static void gui_setup_refresh(DisplayState *ds)
 void graphic_hw_update_done(QemuConsole *con)
 {
     if (con) {
-        qemu_co_queue_restart_all(&con->dump_queue);
+        qemu_co_enter_all(&con->dump_queue, NULL);
     }
 }
 
diff --git a/util/qemu-coroutine-lock.c b/util/qemu-coroutine-lock.c
index 5705cfea2e..5b0342faed 100644
--- a/util/qemu-coroutine-lock.c
+++ b/util/qemu-coroutine-lock.c
@@ -108,6 +108,13 @@ bool coroutine_fn qemu_co_queue_next(CoQueue *queue)
     return qemu_co_enter_next_impl(queue, NULL);
 }
 
+void qemu_co_enter_all_impl(CoQueue *queue, QemuLockable *lock)
+{
+    while (qemu_co_enter_next_impl(queue, lock)) {
+        /* just loop */
+    }
+}
+
 bool qemu_co_queue_empty(CoQueue *queue)
 {
     return QSIMPLEQ_FIRST(&queue->entries) == NULL;
-- 
2.35.1

On Wed, Apr 27, 2022 at 03:08:29PM +0200, Paolo Bonzini wrote:
> Because qemu_co_queue_restart_all does not release the lock, it should
> be used only in coroutine context.  Introduce a new function that,
> like qemu_co_enter_next, does release the lock, and use it whenever
> qemu_co_queue_restart_all was used outside coroutine context.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  include/qemu/coroutine.h   | 13 +++++++++++++
>  ui/console.c               |  2 +-
>  util/qemu-coroutine-lock.c |  7 +++++++
>  3 files changed, 21 insertions(+), 1 deletion(-)
> 
> diff --git a/include/qemu/coroutine.h b/include/qemu/coroutine.h
> index c23d41e1ff..e5954635f6 100644
> --- a/include/qemu/coroutine.h
> +++ b/include/qemu/coroutine.h
> @@ -234,6 +234,19 @@ void qemu_co_queue_restart_all(CoQueue *queue);
>      qemu_co_enter_next_impl(queue, QEMU_MAKE_LOCKABLE(lock))
>  bool qemu_co_enter_next_impl(CoQueue *queue, QemuLockable *lock);
>  
> +/**
> + * Empties the CoQueue, waking the waiting coroutine one at a time.  Unlike

maybe s/coroutine/coroutine(s)/

> + * qemu_co_queue_all, this function releases the lock during aio_co_wake
> + * because it is meant to be used outside coroutine context; in that case, the
> + * coroutine is entered immediately, before qemu_co_enter_all returns.
> + *
> + * If used in coroutine context, qemu_co_enter_all is equivalent to
> + * qemu_co_queue_all.
> + */
> +#define qemu_co_enter_all(queue, lock) \
> +    qemu_co_enter_all_impl(queue, QEMU_MAKE_LOCKABLE(lock))
> +void qemu_co_enter_all_impl(CoQueue *queue, QemuLockable *lock);
> +

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org