[AI] Fix object mask concurrency and shape-lifetime bugs

src/common/ai/segmentation.c

@@ -570,15 +570,16 @@ void dt_seg_warmup_decoder(dt_seg_context_t *ctx)
         .shape = has_mask_shape, .ndim = 1};
 
     int64_t masks_shape[4] = {1, nm, dec_h, dec_w};
+    // shapes must outlive outputs[] used by dt_ai_run below
+    int64_t iou_shape[2] = {1, nm};
+    int64_t lr_shape[4] = {1, nm, pm_dim, pm_dim};
     float iou_buf[MAX_NUM_MASKS];
 
     dt_ai_tensor_t outputs[3];
     int n_out;
 
     if(is_sam)
     {
-      int64_t iou_shape[2] = {1, nm};
-      int64_t lr_shape[4] = {1, nm, pm_dim, pm_dim};
       const int dec_outputs = dt_ai_get_output_count(ctx->decoder);
 
       outputs[0] = (dt_ai_tensor_t){
@@ -847,14 +848,16 @@ float *dt_seg_compute_mask(dt_seg_context_t *ctx,
   dt_ai_tensor_t dec_outputs[3];
   int n_dec_out;
   int64_t masks_shape[4] = {1, nm, dec_h, dec_w};
+  // shapes must outlive dec_outputs[] used by dt_ai_run below
+  int64_t iou_shape[2] = {1, nm};
+  int64_t low_res_shape[4] = {1, nm, pm_dim, pm_dim};
 
   float iou_pred[MAX_NUM_MASKS];
   float *low_res = NULL;
 
   if(is_sam)
   {
     // SAM: masks [1,N,H,W] + iou [1,N], optionally low_res [1,N,pm,pm]
-    int64_t iou_shape[2] = {1, nm};
     const int dec_out_count = dt_ai_get_output_count(ctx->decoder);
 
     dec_outputs[0] = (dt_ai_tensor_t){
@@ -875,7 +878,6 @@ float *dt_seg_compute_mask(dt_seg_context_t *ctx,
         g_free(masks);
         return NULL;
       }
-      int64_t low_res_shape[4] = {1, nm, pm_dim, pm_dim};
       dec_outputs[2] = (dt_ai_tensor_t){
         .data = low_res, .type = DT_AI_FLOAT, .shape = low_res_shape, .ndim = 4};
       n_dec_out = 3;

src/develop/masks/object.c

@@ -425,12 +425,9 @@ static gpointer _encode_thread_func(gpointer data)
     dt_seg_disk_cache_save(d->seg, imgid, distort_hash,
                            rgb, out_w, out_h);
 
-  // signal ready immediately so the user can start placing points,
-  // the warmup below continues on this background thread - if the user
-  // clicks before it finishes, ORT serializes concurrent Run() calls on
-  // the same session, so the decode simply waits for the warmup to
-  // complete first - in practice, users need a moment to position their
-  // cursor, so the ~1 s warmup usually finishes before the first click
+  // signal ready so the user can start placing points; warmup continues
+  // on this thread; _run_decoder joins the thread on the first click to
+  // avoid a race with warmup on the shared segmentation context
   g_atomic_int_set(&d->encode_state, ok ? ENCODE_READY : ENCODE_ERROR);
 
   // warm up decoder with real encoder embeddings so the first user click
@@ -690,6 +687,13 @@ static void _run_decoder(dt_masks_form_gui_t *gui)
   if(gui->guipoints_count <= 0)
     return;
 
+  // wait for encode thread: warmup may still be running after ENCODE_READY
+  if(d->encode_thread)
+  {
+    g_thread_join(d->encode_thread);
+    d->encode_thread = NULL;
+  }
+
   dt_gui_cursor_set_busy();
 
   const float *gp = dt_masks_dynbuf_buffer(gui->guipoints);