[PATCH 2/6] migration: Kick postcopy threads on cancel

[Fabiano Rosas]

Make sure postcopy threads are released when migrate_cancel is
issued. Kick the postcopy_pause semaphore and have the fault thread
read 'fault_thread_quit' when joining.

While here fix the comment mentioning userfault_event_fd.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 migration/migration.c    | 14 +++++++++++---
 migration/postcopy-ram.c | 14 ++++++++++++--
 2 files changed, 23 insertions(+), 5 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 8c5bd0a75c..07fbb5c9f4 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -105,7 +105,7 @@ static bool migration_object_check(MigrationState *ms, 
Error **errp);
 static int migration_maybe_pause(MigrationState *s,
                                  int *current_active_state,
                                  int new_state);
-static void migrate_fd_cancel(MigrationState *s);
+static void migrate_fd_cancel(MigrationState *s, MigrationIncomingState *mis);
 static bool close_return_path_on_source(MigrationState *s);
 static void migration_completion_end(MigrationState *s);
 
@@ -317,7 +317,7 @@ void migration_cancel(const Error *error)
     if (migrate_dirty_limit()) {
         qmp_cancel_vcpu_dirty_limit(false, -1, NULL);
     }
-    migrate_fd_cancel(current_migration);
+    migrate_fd_cancel(current_migration, current_incoming);
 }
 
 void migration_shutdown(void)
@@ -1502,7 +1502,7 @@ static void migrate_fd_error(MigrationState *s, const 
Error *error)
     migrate_set_error(s, error);
 }
 
-static void migrate_fd_cancel(MigrationState *s)
+static void migrate_fd_cancel(MigrationState *s, MigrationIncomingState *mis)
 {
     int old_state ;
 
@@ -1515,6 +1515,12 @@ static void migrate_fd_cancel(MigrationState *s)
         }
     }
 
+    if (mis->state == MIGRATION_STATUS_POSTCOPY_PAUSED) {
+        migrate_set_state(&mis->state, MIGRATION_STATUS_POSTCOPY_PAUSED,
+                          MIGRATION_STATUS_CANCELLING);
+        qemu_sem_post(&mis->postcopy_pause_sem_dst);
+    }
+
     do {
         old_state = s->state;
         if (!migration_is_running()) {
@@ -1523,6 +1529,8 @@ static void migrate_fd_cancel(MigrationState *s)
         /* If the migration is paused, kick it out of the pause */
         if (old_state == MIGRATION_STATUS_PRE_SWITCHOVER) {
             qemu_sem_post(&s->pause_sem);
+        } else if (old_state == MIGRATION_STATUS_POSTCOPY_PAUSED) {
+            qemu_sem_post(&s->postcopy_pause_sem);
         }
         migrate_set_state(&s->state, old_state, MIGRATION_STATUS_CANCELLING);
     } while (s->state != MIGRATION_STATUS_CANCELLING);
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index a535fd2e30..6882ef977d 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -634,6 +634,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState 
*mis)
         qatomic_set(&mis->fault_thread_quit, 1);
         postcopy_fault_thread_notify(mis);
         trace_postcopy_ram_incoming_cleanup_join();
+        qemu_sem_post(&mis->postcopy_pause_sem_fault);
         qemu_thread_join(&mis->fault_thread);
 
         if (postcopy_notify(POSTCOPY_NOTIFY_INBOUND_END, &local_err)) {
@@ -991,8 +992,7 @@ static void *postcopy_ram_fault_thread(void *opaque)
 
         /*
          * We're mainly waiting for the kernel to give us a faulting HVA,
-         * however we can be told to quit via userfault_quit_fd which is
-         * an eventfd
+         * however we can be told to quit via userfault_event_fd.
          */
 
         poll_result = poll(pfd, pfd_len, -1 /* Wait forever */);
@@ -1008,6 +1008,11 @@ static void *postcopy_ram_fault_thread(void *opaque)
              * the channel is rebuilt.
              */
             postcopy_pause_fault_thread(mis);
+
+            if (qatomic_read(&mis->fault_thread_quit)) {
+                trace_postcopy_ram_fault_thread_quit();
+                break;
+            }
         }
 
         if (pfd[1].revents) {
@@ -1082,6 +1087,11 @@ retry:
             if (ret) {
                 /* May be network failure, try to wait for recovery */
                 postcopy_pause_fault_thread(mis);
+
+                if (qatomic_read(&mis->fault_thread_quit)) {
+                    trace_postcopy_ram_fault_thread_quit();
+                    break;
+                }
                 goto retry;
             }
         }
-- 
2.35.3