FuriThread: Improve state callbacks (#3881)

State callbacks assumed they were invoked from the thread that changed
its state, but this wasn't true for FuriThreadStateStarting in the past,
and now it's not true for FuriThreadStateStopped either.

Now it is safe to release the thread memory form the state callback
once it switches to FuriThreadStateStopped. Therefore, pending deletion
calls can be removed.

Co-authored-by: Aleksandr Kutuzov <alleteam@gmail.com>

applications/services/loader/loader.c

@@ -308,12 +308,14 @@ static void loader_applications_closed_callback(void* context) {
     furi_message_queue_put(loader->queue, &message, FuriWaitForever);
 }
 
-static void loader_thread_state_callback(FuriThreadState thread_state, void* context) {
+static void
+    loader_thread_state_callback(FuriThread* thread, FuriThreadState thread_state, void* context) {
+    UNUSED(thread);
     furi_assert(context);
 
-    Loader* loader = context;
-
     if(thread_state == FuriThreadStateStopped) {
+        Loader* loader = context;
+
         LoaderMessage message;
         message.type = LoaderMessageTypeAppClosed;
         furi_message_queue_put(loader->queue, &message, FuriWaitForever);

applications/services/region/region.c

@@ -104,19 +104,12 @@ static int32_t region_load_file(void* context) {
     return 0;
 }
 
-static void region_loader_pending_callback(void* context, uint32_t arg) {
-    UNUSED(arg);
-
-    FuriThread* loader = context;
-    furi_thread_join(loader);
-    furi_thread_free(loader);
-}
-
-static void region_loader_state_callback(FuriThreadState state, void* context) {
+static void
+    region_loader_release_callback(FuriThread* thread, FuriThreadState state, void* context) {
     UNUSED(context);
 
     if(state == FuriThreadStateStopped) {
-        furi_timer_pending_callback(region_loader_pending_callback, furi_thread_get_current(), 0);
+        furi_thread_free(thread);
     }
 }
 
@@ -126,7 +119,7 @@ static void region_storage_callback(const void* message, void* context) {
 
     if(event->type == StorageEventTypeCardMount) {
         FuriThread* loader = furi_thread_alloc_ex(NULL, 2048, region_load_file, NULL);
-        furi_thread_set_state_callback(loader, region_loader_state_callback);
+        furi_thread_set_state_callback(loader, region_loader_release_callback);
         furi_thread_start(loader);
     }
 }

applications/services/rpc/rpc.c

@@ -67,7 +67,7 @@ static RpcSystemCallbacks rpc_systems[] = {
 struct RpcSession {
     Rpc* rpc;
 
-    FuriThread* thread;
+    FuriThreadId thread_id;
 
     RpcHandlerDict_t handlers;
     FuriStreamBuffer* stream;
@@ -172,7 +172,7 @@ size_t rpc_session_feed(
 
     size_t bytes_sent = furi_stream_buffer_send(session->stream, encoded_bytes, size, timeout);
 
-    furi_thread_flags_set(furi_thread_get_id(session->thread), RpcEvtNewData);
+    furi_thread_flags_set(session->thread_id, RpcEvtNewData);
 
     return bytes_sent;
 }
@@ -220,7 +220,7 @@ bool rpc_pb_stream_read(pb_istream_t* istream, pb_byte_t* buf, size_t count) {
                     break;
                 } else {
                     /* Save disconnect flag and continue reading buffer */
-                    furi_thread_flags_set(furi_thread_get_id(session->thread), RpcEvtDisconnect);
+                    furi_thread_flags_set(session->thread_id, RpcEvtDisconnect);
                 }
             } else if(flags & RpcEvtNewData) {
                 // Just wake thread up
@@ -347,35 +347,32 @@ static int32_t rpc_session_worker(void* context) {
     return 0;
 }
 
-static void rpc_session_thread_pending_callback(void* context, uint32_t arg) {
-    UNUSED(arg);
-    RpcSession* session = (RpcSession*)context;
-
-    for(size_t i = 0; i < COUNT_OF(rpc_systems); ++i) {
-        if(rpc_systems[i].free) {
-            (rpc_systems[i].free)(session->system_contexts[i]);
-        }
-    }
-    free(session->system_contexts);
-    free(session->decoded_message);
-    RpcHandlerDict_clear(session->handlers);
-    furi_stream_buffer_free(session->stream);
-
-    furi_mutex_acquire(session->callbacks_mutex, FuriWaitForever);
-    if(session->terminated_callback) {
-        session->terminated_callback(session->context);
-    }
-    furi_mutex_release(session->callbacks_mutex);
-
-    furi_mutex_free(session->callbacks_mutex);
-    furi_thread_join(session->thread);
-    furi_thread_free(session->thread);
-    free(session);
-}
-
-static void rpc_session_thread_state_callback(FuriThreadState thread_state, void* context) {
+static void rpc_session_thread_release_callback(
+    FuriThread* thread,
+    FuriThreadState thread_state,
+    void* context) {
     if(thread_state == FuriThreadStateStopped) {
-        furi_timer_pending_callback(rpc_session_thread_pending_callback, context, 0);
+        RpcSession* session = (RpcSession*)context;
+
+        for(size_t i = 0; i < COUNT_OF(rpc_systems); ++i) {
+            if(rpc_systems[i].free) {
+                (rpc_systems[i].free)(session->system_contexts[i]);
+            }
+        }
+        free(session->system_contexts);
+        free(session->decoded_message);
+        RpcHandlerDict_clear(session->handlers);
+        furi_stream_buffer_free(session->stream);
+
+        furi_mutex_acquire(session->callbacks_mutex, FuriWaitForever);
+        if(session->terminated_callback) {
+            session->terminated_callback(session->context);
+        }
+        furi_mutex_release(session->callbacks_mutex);
+
+        furi_mutex_free(session->callbacks_mutex);
+        furi_thread_free(thread);
+        free(session);
     }
 }
 
@@ -407,12 +404,14 @@ RpcSession* rpc_session_open(Rpc* rpc, RpcOwner owner) {
     };
     rpc_add_handler(session, PB_Main_stop_session_tag, &rpc_handler);
 
-    session->thread = furi_thread_alloc_ex("RpcSessionWorker", 3072, rpc_session_worker, session);
+    FuriThread* thread =
+        furi_thread_alloc_ex("RpcSessionWorker", 3072, rpc_session_worker, session);
+    session->thread_id = furi_thread_get_id(thread);
 
-    furi_thread_set_state_context(session->thread, session);
-    furi_thread_set_state_callback(session->thread, rpc_session_thread_state_callback);
+    furi_thread_set_state_context(thread, session);
+    furi_thread_set_state_callback(thread, rpc_session_thread_release_callback);
 
-    furi_thread_start(session->thread);
+    furi_thread_start(thread);
 
     return session;
 }
@@ -424,7 +423,7 @@ void rpc_session_close(RpcSession* session) {
     rpc_session_set_send_bytes_callback(session, NULL);
     rpc_session_set_close_callback(session, NULL);
     rpc_session_set_buffer_is_empty_callback(session, NULL);
-    furi_thread_flags_set(furi_thread_get_id(session->thread), RpcEvtDisconnect);
+    furi_thread_flags_set(session->thread_id, RpcEvtDisconnect);
 }
 
 void rpc_on_system_start(void* p) {

applications/system/updater/util/update_task.c

@@ -395,14 +395,15 @@ bool update_task_open_file(UpdateTask* update_task, FuriString* filename) {
     return open_success;
 }
 
-static void update_task_worker_thread_cb(FuriThreadState state, void* context) {
-    UpdateTask* update_task = context;
+static void
+    update_task_worker_thread_cb(FuriThread* thread, FuriThreadState state, void* context) {
+    UNUSED(context);
 
     if(state != FuriThreadStateStopped) {
         return;
     }
 
-    if(furi_thread_get_return_code(update_task->thread) == UPDATE_TASK_NOERR) {
+    if(furi_thread_get_return_code(thread) == UPDATE_TASK_NOERR) {
         furi_delay_ms(UPDATE_DELAY_OPERATION_OK);
         furi_hal_power_reset();
     }
@@ -427,7 +428,6 @@ UpdateTask* update_task_alloc(void) {
         furi_thread_alloc_ex("UpdateWorker", 5120, NULL, update_task);
 
     furi_thread_set_state_callback(thread, update_task_worker_thread_cb);
-    furi_thread_set_state_context(thread, update_task);
 #ifdef FURI_RAM_EXEC
     UNUSED(update_task_worker_backup_restore);
     furi_thread_set_callback(thread, update_task_worker_flash_writer);

furi/core/thread.c

@@ -33,7 +33,7 @@ struct FuriThread {
     StaticTask_t container;
     StackType_t* stack_buffer;
 
-    FuriThreadState state;
+    volatile FuriThreadState state;
     int32_t ret;
 
     FuriThreadCallback callback;
@@ -59,7 +59,6 @@ struct FuriThread {
     // this ensures that the size of this structure is minimal
     bool is_service;
     bool heap_trace_enabled;
-    volatile bool is_active;
 };
 
 // IMPORTANT: container MUST be the FIRST struct member
@@ -84,7 +83,7 @@ static void furi_thread_set_state(FuriThread* thread, FuriThreadState state) {
     furi_assert(thread);
     thread->state = state;
     if(thread->state_callback) {
-        thread->state_callback(state, thread->state_context);
+        thread->state_callback(thread, state, thread->state_context);
     }
 }
 
@@ -124,7 +123,7 @@ static void furi_thread_body(void* context) {
     // flush stdout
     __furi_thread_stdout_flush(thread);
 
-    furi_thread_set_state(thread, FuriThreadStateStopped);
+    furi_thread_set_state(thread, FuriThreadStateStopping);
 
     vTaskDelete(NULL);
     furi_thread_catch();
@@ -207,7 +206,6 @@ void furi_thread_free(FuriThread* thread) {
     furi_check(thread->is_service == false);
     // Cannot free a non-joined thread
     furi_check(thread->state == FuriThreadStateStopped);
-    furi_check(!thread->is_active);
 
     furi_thread_set_name(thread, NULL);
     furi_thread_set_appid(thread, NULL);
@@ -349,8 +347,6 @@ void furi_thread_start(FuriThread* thread) {
 
     uint32_t stack_depth = thread->stack_size / sizeof(StackType_t);
 
-    thread->is_active = true;
-
     furi_check(
         xTaskCreateStatic(
             furi_thread_body,
@@ -368,7 +364,7 @@ void furi_thread_cleanup_tcb_event(TaskHandle_t task) {
         // clear thread local storage
         vTaskSetThreadLocalStoragePointer(task, 0, NULL);
         furi_check(thread == (FuriThread*)task);
-        thread->is_active = false;
+        furi_thread_set_state(thread, FuriThreadStateStopped);
     }
 }
 
@@ -383,8 +379,8 @@ bool furi_thread_join(FuriThread* thread) {
     //
     // If your thread exited, but your app stuck here: some other thread uses
     // all cpu time, which delays kernel from releasing task handle
-    while(thread->is_active) {
-        furi_delay_ms(10);
+    while(thread->state != FuriThreadStateStopped) {
+        furi_delay_tick(2);
     }
 
     return true;

furi/core/thread.h

@@ -21,7 +21,8 @@ extern "C" {
  * Many of the FuriThread functions MUST ONLY be called when the thread is STOPPED.
  */
 typedef enum {
-    FuriThreadStateStopped, /**< Thread is stopped */
+    FuriThreadStateStopped, /**< Thread is stopped and is safe to release */
+    FuriThreadStateStopping, /**< Thread is stopping */
     FuriThreadStateStarting, /**< Thread is starting */
     FuriThreadStateRunning, /**< Thread is running */
 } FuriThreadState;
@@ -80,10 +81,11 @@ typedef void (*FuriThreadStdoutWriteCallback)(const char* data, size_t size);
  *
  * The function to be used as a state callback MUST follow this signature.
  *
+ * @param[in] pointer to the FuriThread instance that changed the state
  * @param[in] state identifier of the state the thread has transitioned to
  * @param[in,out] context pointer to a user-specified object
  */
-typedef void (*FuriThreadStateCallback)(FuriThreadState state, void* context);
+typedef void (*FuriThreadStateCallback)(FuriThread* thread, FuriThreadState state, void* context);
 
 /**
  * @brief Signal handler callback function pointer type.

targets/f18/api_symbols.csv

@@ -1,5 +1,5 @@
 entry,status,name,type,params
-Version,+,75.0,,
+Version,+,76.0,,
 Header,+,applications/services/bt/bt_service/bt.h,,
 Header,+,applications/services/bt/bt_service/bt_keys_storage.h,,
 Header,+,applications/services/cli/cli.h,,

targets/f7/api_symbols.csv

@@ -1,5 +1,5 @@
 entry,status,name,type,params
-Version,+,75.0,,
+Version,+,76.0,,
 Header,+,applications/drivers/subghz/cc1101_ext/cc1101_ext_interconnect.h,,
 Header,+,applications/services/bt/bt_service/bt.h,,
 Header,+,applications/services/bt/bt_service/bt_keys_storage.h,,