Cleanup: Comments of wmJobs callbacks.

source/blender/windowmanager/intern/wm_jobs.c

@@ -76,17 +76,30 @@ struct wmJob {
 
   /** Should store entire own context, for start, update, free */
   void *customdata;
-  /** To prevent cpu overhead,
-   * use this one which only gets called when job really starts, not in thread */
+  /**
+   * To prevent cpu overhead, use this one which only gets called when job really starts.
+   * Executed in main thread.
+   */
   void (*initjob)(void *);
-  /** This runs inside thread, and does full job */
+  /**
+   * This performs the actual parallel work.
+   * Executed in worker thread(s).
+   */
   void (*startjob)(void *, short *stop, short *do_update, float *progress);
-  /** Update gets called if thread defines so, and max once per timerstep
-   * it runs outside thread, blocking blender, no drawing! */
+  /**
+   * Called if thread defines so (see `do_update` flag), and max once per timer step.
+   * Executed in main thread.
+   */
   void (*update)(void *);
-  /** Free entire customdata, doesn't run in thread */
+  /**
+   * Free callback (typically for customdata).
+   * Executed in main thread.
+   */
   void (*free)(void *);
-  /** Gets called when job is stopped, not in thread */
+  /**
+   * Called when job is stopped.
+   * Executed in main thread.
+   */
   void (*endjob)(void *);
 
   /** Running jobs each have own timer */