[PATCH 3/6] block: convert bdrv_graph_wrlock() to AIO_WAIT_WHILE_UNLOCKED()

[Stefan Hajnoczi <stefanha@redhat.com>]

The following conversion is safe and does not change behavior:

     GLOBAL_STATE_CODE();
     ...
  -  AIO_WAIT_WHILE(qemu_get_aio_context(), ...);
  +  AIO_WAIT_WHILE_UNLOCKED(NULL, ...);

Since we're in GLOBAL_STATE_CODE(), qemu_get_aio_context() is our home
thread's AioContext. Thus AIO_WAIT_WHILE() does not unlock the
AioContext:

  if (ctx_ && in_aio_context_home_thread(ctx_)) {                \
      while ((cond)) {                                           \
          aio_poll(ctx_, true);                                  \
          waited_ = true;                                        \
      }                                                          \

And that means AIO_WAIT_WHILE_UNLOCKED(NULL, ...) can be substituted.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 block/graph-lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/graph-lock.c b/block/graph-lock.c
index 454c31e691..639526608f 100644
--- a/block/graph-lock.c
+++ b/block/graph-lock.c
@@ -127,7 +127,7 @@ void bdrv_graph_wrlock(void)
          * reader lock.
          */
         qatomic_set(&has_writer, 0);
-        AIO_WAIT_WHILE(qemu_get_aio_context(), reader_count() >= 1);
+        AIO_WAIT_WHILE_UNLOCKED(NULL, reader_count() >= 1);
         qatomic_set(&has_writer, 1);
 
         /*
-- 
2.39.2