[Qemu-devel] [PATCH v3 resend 6/8] rdma: allow state transitions between other states besides ACTIVE

[mrhines@linux.vnet.ibm.com]

From: "Michael R. Hines" <mrhines@us.ibm.com>

This patch is in preparation for the next ones: Until now the MIG_STATE_SETUP
state was not really a 'formal' state. It has been used as a 'zero' state
and QEMU has been unconditionally transitioning into this state when
the QMP migrate command was called. In preparation for timing this state,
we have to make this state a a 'real' state which actually gets transitioned
from later in the migration_thread() from SETUP => ACTIVE, rather than just
automatically dropping into this state at the beginninig of the migration.

This means that the state transition function (migration_finish_set_state())
needs to be capable of transitioning from valid states _other_ than just
MIG_STATE_ACTIVE.

The function is in fact already capable of doing that, but was not allowing the
old state to be a parameter specified as an input.

This patch fixes that and only makes the transition if the current state
matches the old state that the caller intended to transition from.

Reviewed-by: Juan Quintela <quintela@redhat.com>
Tested-by: Michael R. Hines <mrhines@us.ibm.com>
Signed-off-by: Michael R. Hines <mrhines@us.ibm.com>
---
 migration.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/migration.c b/migration.c
index 2bfe245..d212871 100644
--- a/migration.c
+++ b/migration.c
@@ -295,9 +295,9 @@ static void migrate_fd_cleanup(void *opaque)
     notifier_list_notify(&migration_state_notifiers, s);
 }
 
-static void migrate_finish_set_state(MigrationState *s, int new_state)
+static void migrate_set_state(MigrationState *s, int old_state, int new_state)
 {
-    if (atomic_cmpxchg(&s->state, MIG_STATE_ACTIVE, new_state) == new_state) {
+    if (atomic_cmpxchg(&s->state, old_state, new_state) == new_state) {
         trace_migrate_set_state(new_state);
     }
 }
@@ -315,7 +315,7 @@ static void migrate_fd_cancel(MigrationState *s)
 {
     DPRINTF("cancelling migration\n");
 
-    migrate_finish_set_state(s, MIG_STATE_CANCELLED);
+    migrate_set_state(s, s->state, MIG_STATE_CANCELLED);
 }
 
 void add_migration_state_change_notifier(Notifier *notify)
@@ -545,14 +545,14 @@ static void *migration_thread(void *opaque)
                 qemu_savevm_state_complete(s->file);
                 qemu_mutex_unlock_iothread();
                 if (!qemu_file_get_error(s->file)) {
-                    migrate_finish_set_state(s, MIG_STATE_COMPLETED);
+                    migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_COMPLETED);
                     break;
                 }
             }
         }
 
         if (qemu_file_get_error(s->file)) {
-            migrate_finish_set_state(s, MIG_STATE_ERROR);
+            migrate_set_state(s, MIG_STATE_ACTIVE, MIG_STATE_ERROR);
             break;
         }
         current_time = qemu_get_clock_ms(rt_clock);
-- 
1.7.10.4