[3/6] migration: notify migration state before starting thread

Submitted by Stefan Hajnoczi on July 29, 2013, 3:36 p.m.


Message ID 1375112172-24863-4-git-send-email-stefanha@redhat.com
State New
Headers show

Commit Message

Stefan Hajnoczi July 29, 2013, 3:36 p.m.
The migration thread runs outside the QEMU global mutex when possible.
Therefore we must notify migration state change *before* starting the
migration thread.

This allows registered listeners to act before live migration iterations
begin.  Therefore they can get into a state that allows for live
migration.  When the migration thread starts everything will be ready.

Without this patch there is a race condition during migration setup,
depending on whether the migration thread has already transitioned from
SETUP to ACTIVE state.

Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
 migration.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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diff --git a/migration.c b/migration.c
index e12e784..a5ed26b 100644
--- a/migration.c
+++ b/migration.c
@@ -658,7 +658,9 @@  void migrate_fd_connect(MigrationState *s)
                              s->bandwidth_limit / XFER_LIMIT_RATIO);
+    /* Notify before starting migration thread */
+    notifier_list_notify(&migration_state_notifiers, s);
     qemu_thread_create(&s->thread, migration_thread, s,
-    notifier_list_notify(&migration_state_notifiers, s);