[PULL 25/31] migration/colo: Replace QemuSemaphore with QemuEvent

[Paolo Bonzini <pbonzini@redhat.com>]

From: Akihiko Odaki <akihiko.odaki@daynix.com>

colo_exit_sem and colo_incoming_sem represent one-shot events so they
can be converted into QemuEvent, which is more lightweight.

Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/r/20250529-event-v5-8-53b285203794@daynix.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 migration/migration.h |  6 +++---
 migration/colo.c      | 20 ++++++++++----------
 2 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/migration/migration.h b/migration/migration.h
index 21aa6a3c8fe..aaec471c00f 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -186,7 +186,7 @@ struct MigrationIncomingState {
 
     /* The coroutine we should enter (back) after failover */
     Coroutine *colo_incoming_co;
-    QemuSemaphore colo_incoming_sem;
+    QemuEvent colo_incoming_event;
 
     /* Optional load threads pool and its thread exit request flag */
     ThreadPool *load_threads;
@@ -381,8 +381,8 @@ struct MigrationState {
     /* Migration is paused due to pause-before-switchover */
     QemuEvent pause_event;
 
-    /* The semaphore is used to notify COLO thread that failover is finished */
-    QemuSemaphore colo_exit_sem;
+    /* The event is used to notify COLO thread that failover is finished */
+    QemuEvent colo_exit_event;
 
     /* The event is used to notify COLO thread to do checkpoint */
     QemuEvent colo_checkpoint_event;
diff --git a/migration/colo.c b/migration/colo.c
index c976b3ff344..e0f713c837f 100644
--- a/migration/colo.c
+++ b/migration/colo.c
@@ -146,7 +146,7 @@ static void secondary_vm_do_failover(void)
         return;
     }
     /* Notify COLO incoming thread that failover work is finished */
-    qemu_sem_post(&mis->colo_incoming_sem);
+    qemu_event_set(&mis->colo_incoming_event);
 
     /* For Secondary VM, jump to incoming co */
     if (mis->colo_incoming_co) {
@@ -195,7 +195,7 @@ static void primary_vm_do_failover(void)
     }
 
     /* Notify COLO thread that failover work is finished */
-    qemu_sem_post(&s->colo_exit_sem);
+    qemu_event_set(&s->colo_exit_event);
 }
 
 COLOMode get_colo_mode(void)
@@ -620,8 +620,8 @@ out:
     }
 
     /* Hope this not to be too long to wait here */
-    qemu_sem_wait(&s->colo_exit_sem);
-    qemu_sem_destroy(&s->colo_exit_sem);
+    qemu_event_wait(&s->colo_exit_event);
+    qemu_event_destroy(&s->colo_exit_event);
 
     /*
      * It is safe to unregister notifier after failover finished.
@@ -651,7 +651,7 @@ void migrate_start_colo_process(MigrationState *s)
     s->colo_delay_timer =  timer_new_ms(QEMU_CLOCK_HOST,
                                 colo_checkpoint_notify_timer, NULL);
 
-    qemu_sem_init(&s->colo_exit_sem, 0);
+    qemu_event_init(&s->colo_exit_event, false);
     colo_process_checkpoint(s);
     bql_lock();
 }
@@ -808,11 +808,11 @@ void colo_shutdown(void)
     case COLO_MODE_PRIMARY:
         s = migrate_get_current();
         qemu_event_set(&s->colo_checkpoint_event);
-        qemu_sem_post(&s->colo_exit_sem);
+        qemu_event_set(&s->colo_exit_event);
         break;
     case COLO_MODE_SECONDARY:
         mis = migration_incoming_get_current();
-        qemu_sem_post(&mis->colo_incoming_sem);
+        qemu_event_set(&mis->colo_incoming_event);
         break;
     default:
         break;
@@ -827,7 +827,7 @@ static void *colo_process_incoming_thread(void *opaque)
     Error *local_err = NULL;
 
     rcu_register_thread();
-    qemu_sem_init(&mis->colo_incoming_sem, 0);
+    qemu_event_init(&mis->colo_incoming_event, false);
 
     migrate_set_state(&mis->state, MIGRATION_STATUS_ACTIVE,
                       MIGRATION_STATUS_COLO);
@@ -923,8 +923,8 @@ out:
     }
 
     /* Hope this not to be too long to loop here */
-    qemu_sem_wait(&mis->colo_incoming_sem);
-    qemu_sem_destroy(&mis->colo_incoming_sem);
+    qemu_event_wait(&mis->colo_incoming_event);
+    qemu_event_destroy(&mis->colo_incoming_event);
 
     rcu_unregister_thread();
     return NULL;
-- 
2.49.0