[PATCH v2 14/23] migration/multifd: Forbid spurious wakeups

[peterx]

From: Peter Xu <peterx@redhat.com>

Now multifd's logic is designed to have no spurious wakeup.  I still
remember a talk to Juan and he seems to agree we should drop it now, and if
my memory was right it was there because multifd used to hit that when
still debugging.

Let's drop it and see what can explode; as long as it's not reaching
soft-freeze.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 migration/multifd.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/migration/multifd.c b/migration/multifd.c
index 6aa44340de..28b54100cd 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -756,7 +756,9 @@ static void *multifd_send_thread(void *opaque)
             p->next_packet_size = 0;
             qatomic_set(&p->pending_job, false);
             qemu_mutex_unlock(&p->mutex);
-        } else if (qatomic_read(&p->pending_sync)) {
+        } else {
+            /* If not a normal job, must be a sync request */
+            assert(qatomic_read(&p->pending_sync));
             p->flags = MULTIFD_FLAG_SYNC;
             multifd_send_fill_packet(p);
             ret = qio_channel_write_all(p->c, (void *)p->packet,
@@ -771,9 +773,6 @@ static void *multifd_send_thread(void *opaque)
             qatomic_set(&p->pending_sync, false);
             qemu_mutex_unlock(&p->mutex);
             qemu_sem_post(&p->sem_sync);
-        } else {
-            qemu_mutex_unlock(&p->mutex);
-            /* sometimes there are spurious wakeups */
         }
     }
 
-- 
2.43.0