aio-wait: Increase num_waiters even in home thread

Even if AIO_WAIT_WHILE() is called in the home context of the
AioContext, we still want to allow the condition to change depending on
other threads as long as they kick the AioWait. Specfically block jobs
can be running in an I/O thread and should then be able to kick a drain
in the main loop context.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>

diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
index c85a62f7989b8be7e83a358cd45922a02ae7f734..600fad183e14b4f6e427323132386d35e66d6b34 100644 (file)
--- a/include/block/aio-wait.h
+++ b/include/block/aio-wait.h
@@ -76,6 +76,8 @@ typedef struct {
     bool waited_ = false;                                          \
     AioWait *wait_ = (wait);                                       \
     AioContext *ctx_ = (ctx);                                      \
+    /* Increment wait_->num_waiters before evaluating cond. */     \
+    atomic_inc(&wait_->num_waiters);                               \
     if (ctx_ && in_aio_context_home_thread(ctx_)) {                \
         while ((cond)) {                                           \
             aio_poll(ctx_, true);                                  \
@@ -84,8 +86,6 @@ typedef struct {
     } else {                                                       \
         assert(qemu_get_current_aio_context() ==                   \
                qemu_get_aio_context());                            \
-        /* Increment wait_->num_waiters before evaluating cond. */ \
-        atomic_inc(&wait_->num_waiters);                           \
         while ((cond)) {                                           \
             if (ctx_) {                                            \
                 aio_context_release(ctx_);                         \
@@ -96,8 +96,8 @@ typedef struct {
             }                                                      \
             waited_ = true;                                        \
         }                                                          \
-        atomic_dec(&wait_->num_waiters);                           \
     }                                                              \
+    atomic_dec(&wait_->num_waiters);                               \
     waited_; })
 
 /**