multifd: Unconditionally unregister yank function

To: qemu-devel <[email protected]>
Cc: "Dr. David Alan Gilbert" <[email protected]>, Juan Quintela
 <[email protected]>, Peter Xu <[email protected]>, Leonardo Bras Soares
 Passos <[email protected]>
Date: Wed, 4 Aug 2021 21:26:32 +0200 (5 weeks, 11 hours, 52 minutes ago)

[[PGP Signed Part:No public key for 35AB0B289C5DB258 created at 2021-08-04T21:26:32+0200 using RSA]]
Unconditionally unregister yank function in multifd_load_cleanup().
If it is not unregistered here, it will leak and cause a crash
in yank_unregister_instance(). Now if the ioc is still in use
afterwards, it will only lead to qemu not being able to recover
from a hang related to that ioc.

After checking the code, i am pretty sure that ref is always 1
when arriving here. So all this currently does is remove the
unneeded check.

Signed-off-by: Lukas Straub <[email protected]>
Reviewed-by: Juan Quintela <[email protected]>
Signed-off-by: Juan Quintela <[email protected]>

Author: lukasstraub2

migration/multifd.c

@@ -991,10 +991,7 @@ int multifd_load_cleanup(Error **errp)
     for (i = 0; i < migrate_multifd_channels(); i++) {
         MultiFDRecvParams *p = &multifd_recv_state->params[i];
 
-        if (OBJECT(p->c)->ref == 1) {
-            migration_ioc_unregister_yank(p->c);
-        }
-
+        migration_ioc_unregister_yank(p->c);
         object_unref(OBJECT(p->c));
         p->c = NULL;
         qemu_mutex_destroy(&p->mutex);