From d4f46c41e0dd921563614ad48e7099eeac06d285 Mon Sep 17 00:00:00 2001
From: Peter Xu <peterx@redhat.com>
Date: Fri, 2 Feb 2024 18:28:48 +0800
Subject: [38/99] migration/multifd: Forbid spurious wakeups

commit 859ebaf346e8b5dece6cf255c604fe953d8ec9ab upstream.

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>
Link: https://lore.kernel.org/r/20240202102857.110210-15-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Jason Zeng <jason.zeng@intel.com>
---
 migration/multifd.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/migration/multifd.c b/migration/multifd.c
index d4528cf9d1..3b7984cf99 100644
--- a/migration/multifd.c
+++ b/migration/multifd.c
@@ -760,7 +760,9 @@ 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,
@@ -775,9 +777,6 @@ 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 */
         }
     }
 
-- 
2.33.0