blockjob: Add block_job_yield()

This will unset busy flag and put coroutine to sleep, can be used to
wait for QMP complete/cancel.

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

1 files changed, 14 insertions, 0 deletions

diff --git a/blockjob.c b/blockjob.c
index 4da86cdfcd..a6db01e953 100644
--- a/blockjob.c
+++ b/blockjob.c
@@ -210,6 +210,20 @@ void block_job_sleep_ns(BlockJob *job, QEMUClockType type, int64_t ns)
     job->busy = true;
 }
 
+void block_job_yield(BlockJob *job)
+{
+    assert(job->busy);
+
+    /* Check cancellation *before* setting busy = false, too!  */
+    if (block_job_is_cancelled(job)) {
+        return;
+    }
+
+    job->busy = false;
+    qemu_coroutine_yield();
+    job->busy = true;
+}
+
 BlockJobInfo *block_job_query(BlockJob *job)
 {
     BlockJobInfo *info = g_new0(BlockJobInfo, 1);