command: add a way to abort asynchronous commands

Many asynchronous commands are potentially long running operations, such
as loading something from network or running a foreign process.
Obviously it shouldn't just be possible for them to freeze the player if
they don't terminate as expected. Also, there will be situations where
you want to explicitly stop some of those operations explicitly. So add
an infrastructure for this.

Commands have to support this explicitly. The next commit uses this to
actually add support to a command.

8 files changed, 131 insertions, 9 deletions

diff --git a/player/client.c b/player/client.c
index b6282a1134..31339f47a3 100644
--- a/player/client.c
+++ b/player/client.c
@@ -1063,9 +1063,14 @@ static int run_client_command(mpv_handle *ctx, struct mp_cmd *cmd, mpv_node *res
 
     lock_core(ctx);
     if (async) {
-        run_command(ctx->mpctx, req.cmd, NULL, NULL);
+        run_command(ctx->mpctx, cmd, NULL, NULL, NULL);
     } else {
-        run_command(ctx->mpctx, req.cmd, cmd_complete, &req);
+        struct mp_abort_entry *abort = NULL;
+        if (cmd->def->can_abort) {
+            abort = talloc_zero(NULL, struct mp_abort_entry);
+            abort->client = ctx;
+        }
+        run_command(ctx->mpctx, cmd, abort, cmd_complete, &req);
     }
     unlock_core(ctx);
 
@@ -1129,9 +1134,17 @@ static void async_cmd_fn(void *data)
     ta_xset_parent(cmd, NULL);
     req->cmd = NULL;
 
+    struct mp_abort_entry *abort = NULL;
+    if (cmd->def->can_abort) {
+        abort = talloc_zero(NULL, struct mp_abort_entry);
+        abort->client = req->reply_ctx;
+        abort->client_work_type = MPV_EVENT_COMMAND_REPLY;
+        abort->client_work_id = req->userdata;
+    }
+
     // This will synchronously or asynchronously call cmd_complete (depending
     // on the command).
-    run_command(req->mpctx, cmd, async_cmd_complete, req);
+    run_command(req->mpctx, cmd, abort, async_cmd_complete, req);
 }
 
 static int run_async_cmd(mpv_handle *ctx, uint64_t ud, struct mp_cmd *cmd)
@@ -1163,6 +1176,23 @@ int mpv_command_node_async(mpv_handle *ctx, uint64_t ud, mpv_node *args)
     return run_async_cmd(ctx, ud, mp_input_parse_cmd_node(ctx->log, args));
 }
 
+void mpv_abort_async_command(mpv_handle *ctx, uint64_t reply_userdata)
+{
+    struct MPContext *mpctx = ctx->mpctx;
+
+    pthread_mutex_lock(&mpctx->abort_lock);
+    for (int n = 0; n < mpctx->num_abort_list; n++) {
+        struct mp_abort_entry *abort = mpctx->abort_list[n];
+        if (abort->client == ctx &&
+            abort->client_work_type == MPV_EVENT_COMMAND_REPLY &&
+            abort->client_work_id == reply_userdata)
+        {
+            mp_abort_trigger_locked(mpctx, abort);
+        }
+    }
+    pthread_mutex_unlock(&mpctx->abort_lock);
+}
+
 static int translate_property_error(int errc)
 {
     switch (errc) {
diff --git a/player/command.c b/player/command.c
index f2d7eedd5f..cd623c03f4 100644
--- a/player/command.c
+++ b/player/command.c
@@ -4865,7 +4865,7 @@ static void continue_cmd_list(struct cmd_list_ctx *list)
 
         if (sub->flags & MP_ASYNC_CMD) {
             // We run it "detached" (fire & forget)
-            run_command(list->mpctx, sub, NULL, NULL);
+            run_command(list->mpctx, sub, NULL, NULL, NULL);
         } else {
             // Run the next command once this one completes.
 
@@ -4873,7 +4873,7 @@ static void continue_cmd_list(struct cmd_list_ctx *list)
             list->current_valid = true;
             list->current = pthread_self();
 
-            run_command(list->mpctx, sub, on_cmd_list_sub_completion, list);
+            run_command(list->mpctx, sub, NULL, on_cmd_list_sub_completion, list);
 
             list->current_valid = false;
 
@@ -4920,8 +4920,9 @@ void mp_cmd_ctx_complete(struct mp_cmd_ctx *cmd)
         mpv_free_node_contents(&cmd->result);
     if (cmd->on_completion)
         cmd->on_completion(cmd);
+    if (cmd->abort)
+        mp_abort_remove(cmd->mpctx, cmd->abort);
     mpv_free_node_contents(&cmd->result);
-    talloc_free(cmd->cmd);
     talloc_free(cmd);
 }
 
@@ -4949,27 +4950,40 @@ static void run_command_on_worker_thread(void *p)
 // function returns (the caller is supposed to be able to handle both cases). In
 // both cases, the callback will be called while the core is locked (i.e. you
 // can access the core freely).
+// If abort is non-NULL, then the caller creates the abort object. It must have
+// been allocated with talloc. run_command() will register/unregister/destroy
+// it. Must not be set if cmd->def->can_abort==false.
 // on_completion_priv is copied to mp_cmd_ctx.on_completion_priv and can be
 // accessed from the completion callback.
 // The completion callback is invoked exactly once. If it's NULL, it's ignored.
 // Ownership of cmd goes to the caller.
 void run_command(struct MPContext *mpctx, struct mp_cmd *cmd,
+                 struct mp_abort_entry *abort,
                  void (*on_completion)(struct mp_cmd_ctx *cmd),
                  void *on_completion_priv)
 {
     struct mp_cmd_ctx *ctx = talloc(NULL, struct mp_cmd_ctx);
     *ctx = (struct mp_cmd_ctx){
         .mpctx = mpctx,
-        .cmd = cmd,
+        .cmd = talloc_steal(ctx, cmd),
         .args = cmd->args,
         .num_args = cmd->nargs,
         .priv = cmd->def->priv,
+        .abort = talloc_steal(ctx, abort),
         .success = true,
         .completed = true,
         .on_completion = on_completion,
         .on_completion_priv = on_completion_priv,
     };
 
+    if (!ctx->abort && cmd->def->can_abort)
+        ctx->abort = talloc_zero(ctx, struct mp_abort_entry);
+
+    assert(cmd->def->can_abort == !!ctx->abort);
+
+    if (ctx->abort)
+        mp_abort_add(mpctx, ctx->abort);
+
     struct MPOpts *opts = mpctx->opts;
     ctx->on_osd = cmd->flags & MP_ON_OSD_FLAGS;
     bool auto_osd = ctx->on_osd == MP_ON_OSD_AUTO;
diff --git a/player/command.h b/player/command.h
index 9e385dbc16..ae3af82886 100644
--- a/player/command.h
+++ b/player/command.h
@@ -45,6 +45,8 @@ struct mp_cmd_ctx {
     bool bar_osd;       // OSD bar requested
     bool seek_msg_osd;  // same as above, but for seek commands
     bool seek_bar_osd;
+    // If mp_cmd_def.can_abort is set, this will be set.
+    struct mp_abort_entry *abort;
     // Return values (to be set by command implementation, read by the
     // completion callback).
     bool success;       // true by default
@@ -64,6 +66,7 @@ struct mp_cmd_ctx {
 };
 
 void run_command(struct MPContext *mpctx, struct mp_cmd *cmd,
+                 struct mp_abort_entry *abort,
                  void (*on_completion)(struct mp_cmd_ctx *cmd),
                  void *on_completion_priv);
 void mp_cmd_ctx_complete(struct mp_cmd_ctx *cmd);
diff --git a/player/core.h b/player/core.h
index 0434c5cb64..a42b1252b8 100644
--- a/player/core.h
+++ b/player/core.h
@@ -442,6 +442,8 @@ typedef struct MPContext {
 
     // --- The following fields are protected by abort_lock
     struct mp_cancel *demuxer_cancel; // cancel handle for MPContext.demuxer
+    struct mp_abort_entry **abort_list;
+    int num_abort_list;
 
     // --- Owned by MPContext
     pthread_t open_thread;
@@ -459,6 +461,20 @@ typedef struct MPContext {
     int open_res_error;
 } MPContext;
 
+// Contains information about an asynchronous work item, how it can be aborted,
+// and when. All fields are protected by MPContext.abort_lock.
+struct mp_abort_entry {
+    // General conditions.
+    bool coupled_to_playback;   // trigger when playback is terminated
+    // Actual trigger to abort the work.
+    struct mp_cancel *cancel;
+    // For client API.
+    struct mpv_handle *client;  // non-NULL if done by a client API user
+    int client_work_type;       // client API type, e.h. MPV_EVENT_COMMAND_REPLY
+    uint64_t client_work_id;    // client API user reply_userdata value
+                                // (only valid if client_work_type set)
+};
+
 // audio.c
 void reset_audio_state(struct MPContext *mpctx);
 void reinit_audio_chain(struct MPContext *mpctx);
@@ -488,6 +504,12 @@ struct playlist_entry *mp_check_playlist_resume(struct MPContext *mpctx,
 
 // loadfile.c
 void mp_abort_playback_async(struct MPContext *mpctx);
+void mp_abort_add(struct MPContext *mpctx, struct mp_abort_entry *abort);
+void mp_abort_remove(struct MPContext *mpctx, struct mp_abort_entry *abort);
+void mp_abort_recheck_locked(struct MPContext *mpctx,
+                             struct mp_abort_entry *abort);
+void mp_abort_trigger_locked(struct MPContext *mpctx,
+                             struct mp_abort_entry *abort);
 void uninit_player(struct MPContext *mpctx, unsigned int mask);
 int mp_add_external_file(struct MPContext *mpctx, char *filename,
                          enum stream_type filter);
diff --git a/player/loadfile.c b/player/loadfile.c
index e1864f3fd5..6f28d2ee38 100644
--- a/player/loadfile.c
+++ b/player/loadfile.c
@@ -67,11 +67,62 @@ void mp_abort_playback_async(struct MPContext *mpctx)
     mp_cancel_trigger(mpctx->playback_abort);
 
     pthread_mutex_lock(&mpctx->abort_lock);
+
     if (mpctx->demuxer_cancel)
         mp_cancel_trigger(mpctx->demuxer_cancel);
+
+    for (int n = 0; n < mpctx->num_abort_list; n++) {
+        struct mp_abort_entry *abort = mpctx->abort_list[n];
+        if (abort->coupled_to_playback)
+            mp_abort_trigger_locked(mpctx, abort);
+    }
+
+    pthread_mutex_unlock(&mpctx->abort_lock);
+}
+
+// Add it to the global list, and allocate required data structures.
+void mp_abort_add(struct MPContext *mpctx, struct mp_abort_entry *abort)
+{
+    pthread_mutex_lock(&mpctx->abort_lock);
+    assert(!abort->cancel);
+    abort->cancel = mp_cancel_new(NULL);
+    MP_TARRAY_APPEND(NULL, mpctx->abort_list, mpctx->num_abort_list, abort);
+    mp_abort_recheck_locked(mpctx, abort);
     pthread_mutex_unlock(&mpctx->abort_lock);
 }
 
+// Remove Add it to the global list, and free/clear required data structures.
+// Does not deallocate the abort value itself.
+void mp_abort_remove(struct MPContext *mpctx, struct mp_abort_entry *abort)
+{
+    pthread_mutex_lock(&mpctx->abort_lock);
+    for (int n = 0; n < mpctx->num_abort_list; n++) {
+        if (mpctx->abort_list[n] == abort) {
+            MP_TARRAY_REMOVE_AT(mpctx->abort_list, mpctx->num_abort_list, n);
+            TA_FREEP(&abort->cancel);
+            abort = NULL; // it's not free'd, just clear for the assert below
+            break;
+        }
+    }
+    assert(!abort); // should have been in the list
+    pthread_mutex_unlock(&mpctx->abort_lock);
+}
+
+// Verify whether the abort needs to be signaled after changing certain fields
+// in abort.
+void mp_abort_recheck_locked(struct MPContext *mpctx,
+                             struct mp_abort_entry *abort)
+{
+    if (abort->coupled_to_playback && mp_cancel_test(mpctx->playback_abort))
+        mp_abort_trigger_locked(mpctx, abort);
+}
+
+void mp_abort_trigger_locked(struct MPContext *mpctx,
+                             struct mp_abort_entry *abort)
+{
+    mp_cancel_trigger(abort->cancel);
+}
+
 static void uninit_demuxer(struct MPContext *mpctx)
 {
     for (int r = 0; r < NUM_PTRACKS; r++) {
diff --git a/player/main.c b/player/main.c
index d744c9cf12..c51f93a430 100644
--- a/player/main.c
+++ b/player/main.c
@@ -189,6 +189,8 @@ void mp_destroy(struct MPContext *mpctx)
     uninit_libav(mpctx->global);
 
     mp_msg_uninit(mpctx->global);
+    assert(!mpctx->num_abort_list);
+    talloc_free(mpctx->abort_list);
     pthread_mutex_destroy(&mpctx->abort_lock);
     talloc_free(mpctx);
 }
diff --git a/player/playloop.c b/player/playloop.c
index 26f9f12d82..a784bfd554 100644
--- a/player/playloop.c
+++ b/player/playloop.c
@@ -110,7 +110,7 @@ void mp_process_input(struct MPContext *mpctx)
         mp_cmd_t *cmd = mp_input_read_cmd(mpctx->input);
         if (!cmd)
             break;
-        run_command(mpctx, cmd, NULL, NULL);
+        run_command(mpctx, cmd, NULL, NULL, NULL);
     }
     mp_set_timeout(mpctx, mp_input_get_delay(mpctx->input));
 }
diff --git a/player/screenshot.c b/player/screenshot.c
index e654ce2081..e24ca051f1 100644
--- a/player/screenshot.c
+++ b/player/screenshot.c
@@ -519,7 +519,7 @@ void screenshot_flip(struct MPContext *mpctx)
 
     struct mp_waiter wait = MP_WAITER_INITIALIZER;
     void *a[] = {mpctx, &wait};
-    run_command(mpctx, mp_cmd_clone(ctx->each_frame), screenshot_fin, a);
+    run_command(mpctx, mp_cmd_clone(ctx->each_frame), NULL, screenshot_fin, a);
 
     // Block (in a reentrant way) until he screenshot was written. Otherwise,
     // we could pile up screenshot requests forever.