Re: [PATCH v2 2/2] vhost-user: add a request-reply lock

[Prasad Pandit]

Hello Michael,

On Thu, 29 Aug 2024 at 13:12, Michael S. Tsirkin <mst@redhat.com> wrote:
> Weird.  Seems to indicate some kind of deadlock?

* Such a deadlock should occur across all environments I guess, not
sure why it happens selectively. It is strange.

> So maybe vhost_user_postcopy_end should take the BQL?
===
diff --git a/migration/savevm.c b/migration/savevm.c
index e7c1215671..31acda3818 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -2050,7 +2050,9 @@ static void *postcopy_ram_listen_thread(void *opaque)
          */
         qemu_event_wait(&mis->main_thread_load_event);
     }
+    bql_lock();
     postcopy_ram_incoming_cleanup(mis);
+    bql_unlock();

     if (load_res < 0) {
         /*
===

* Actually a BQL patch above was tested and it worked fine. But not
sure if it is an acceptable solution. Another contention was taking
BQL could make things more complicated, so a local vhost-user specific
lock should be better.

...wdyt?
---
  - Prasad