migration: Rename thread debug names

The postcopy thread names on dest QEMU are slightly confusing, partly I'll
need to blame myself on 36f62f11e4 ("migration: Postcopy preemption
preparation on channel creation").  E.g., "fault-fast" reads like a fast
version of "fault-default", but it's actually the fast version of
"postcopy/listen".

Taking this chance, rename all the migration threads with proper rules.
Considering we only have 15 chars usable, prefix all threads with "mig/",
meanwhile identify src/dst threads properly this time.  So now most thread
names will look like "mig/DIR/xxx", where DIR will be "src"/"dst", except
the bg-snapshot thread which doesn't have a direction.

For multifd threads, making them "mig/{src|dst}/{send|recv}_%d".

We used to have "live_migration" thread for a very long time, now it's
called "mig/src/main".  We may hope to have "mig/dst/main" soon but not
yet.

Reviewed-by: Fabiano Rosas <farosas@suse.de>
Reviewed-by: Zhijian Li (Fujitsu) <lizhijian@fujitsu.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Fabiano Rosas <farosas@suse.de>

migration/colo.c

@@ -935,7 +935,7 @@ void coroutine_fn colo_incoming_co(void)
     assert(bql_locked());
     assert(migration_incoming_colo_enabled());
 
-    qemu_thread_create(&th, "COLO incoming", colo_process_incoming_thread,
+    qemu_thread_create(&th, "mig/dst/colo", colo_process_incoming_thread,
                        mis, QEMU_THREAD_JOINABLE);
 
     mis->colo_incoming_co = qemu_coroutine_self();

migration/migration.c

@@ -2431,7 +2431,7 @@ static int open_return_path_on_source(MigrationState *ms)
 
     trace_open_return_path_on_source();
 
-    qemu_thread_create(&ms->rp_state.rp_thread, "return path",
+    qemu_thread_create(&ms->rp_state.rp_thread, "mig/src/rp-thr",
                        source_return_path_thread, ms, QEMU_THREAD_JOINABLE);
     ms->rp_state.rp_thread_created = true;
 
@@ -3770,10 +3770,10 @@ void migrate_fd_connect(MigrationState *s, Error *error_in)
     }
 
     if (migrate_background_snapshot()) {
-        qemu_thread_create(&s->thread, "bg_snapshot",
+        qemu_thread_create(&s->thread, "mig/snapshot",
                 bg_migration_thread, s, QEMU_THREAD_JOINABLE);
     } else {
-        qemu_thread_create(&s->thread, "live_migration",
+        qemu_thread_create(&s->thread, "mig/src/main",
                 migration_thread, s, QEMU_THREAD_JOINABLE);
     }
     s->migration_thread_running = true;

migration/multifd.c

@@ -1069,7 +1069,7 @@ static bool multifd_tls_channel_connect(MultiFDSendParams *p,
     args->p = p;
 
     p->tls_thread_created = true;
-    qemu_thread_create(&p->tls_thread, "multifd-tls-handshake-worker",
+    qemu_thread_create(&p->tls_thread, "mig/src/tls",
                        multifd_tls_handshake_thread, args,
                        QEMU_THREAD_JOINABLE);
     return true;
@@ -1190,7 +1190,7 @@ bool multifd_send_setup(void)
             p->packet->magic = cpu_to_be32(MULTIFD_MAGIC);
             p->packet->version = cpu_to_be32(MULTIFD_VERSION);
         }
-        p->name = g_strdup_printf("multifdsend_%d", i);
+        p->name = g_strdup_printf("mig/src/send_%d", i);
         p->page_size = qemu_target_page_size();
         p->page_count = page_count;
         p->write_flags = 0;
@@ -1604,7 +1604,7 @@ int multifd_recv_setup(Error **errp)
                 + sizeof(uint64_t) * page_count;
             p->packet = g_malloc0(p->packet_len);
         }
-        p->name = g_strdup_printf("multifdrecv_%d", i);
+        p->name = g_strdup_printf("mig/dst/recv_%d", i);
         p->normal = g_new0(ram_addr_t, page_count);
         p->zero = g_new0(ram_addr_t, page_count);
         p->page_count = page_count;

migration/postcopy-ram.c

@@ -1238,7 +1238,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
         return -1;
     }
 
-    postcopy_thread_create(mis, &mis->fault_thread, "fault-default",
+    postcopy_thread_create(mis, &mis->fault_thread, "mig/dst/fault",
                            postcopy_ram_fault_thread, QEMU_THREAD_JOINABLE);
     mis->have_fault_thread = true;
 
@@ -1258,7 +1258,7 @@ int postcopy_ram_incoming_setup(MigrationIncomingState *mis)
          * This thread needs to be created after the temp pages because
          * it'll fetch RAM_CHANNEL_POSTCOPY PostcopyTmpPage immediately.
          */
-        postcopy_thread_create(mis, &mis->postcopy_prio_thread, "fault-fast",
+        postcopy_thread_create(mis, &mis->postcopy_prio_thread, "mig/dst/preempt",
                                postcopy_preempt_thread, QEMU_THREAD_JOINABLE);
         mis->preempt_thread_status = PREEMPT_THREAD_CREATED;
     }

migration/savevm.c

@@ -2129,7 +2129,7 @@ static int loadvm_postcopy_handle_listen(MigrationIncomingState *mis)
     }
 
     mis->have_listen_thread = true;
-    postcopy_thread_create(mis, &mis->listen_thread, "postcopy/listen",
+    postcopy_thread_create(mis, &mis->listen_thread, "mig/dst/listen",
                            postcopy_ram_listen_thread, QEMU_THREAD_DETACHED);
     trace_loadvm_postcopy_handle_listen("return");