New API call iso_image_generator_is_running().

Prevented a potential race condition between Ecma119Image disposal by
burn_source and final activities of ISO generator thread.

libisofs/ecma119.c

@@ -59,6 +59,12 @@ void ecma119_image_free(Ecma119Image *t)
 
     if (t == NULL)
         return;
+
+    if (t->refcount > 1) {
+        t->refcount--;
+        return;
+    }
+
     if (t->root != NULL)
         ecma119_node_free(t->root);
     if (t->image != NULL)
@@ -1315,6 +1321,12 @@ void *write_function(void *arg)
     if (res <= 0)
         goto write_error;
 
+    target->image->generator_is_running = 0;
+
+    /* Give up reference claim made in ecma119_image_new().
+       Eventually free target */
+    ecma119_image_free(target);
+
 #ifdef Libisofs_with_pthread_exiT
     pthread_exit(NULL);
 #else
@@ -1340,6 +1352,12 @@ void *write_function(void *arg)
     /* Invalidate the transplanted checksum buffer in IsoImage */
     iso_image_free_checksums(target->image, 0);
 
+    target->image->generator_is_running = 0;
+
+    /* Give up reference claim made in ecma119_image_new().
+       Eventually free target */
+    ecma119_image_free(target);
+
 #ifdef Libisofs_with_pthread_exiT
     pthread_exit(NULL);
 #else
@@ -1460,6 +1478,10 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     if (target == NULL) {
         return ISO_OUT_OF_MEM;
     }
+    /* This reference will be transfered to the burn_source and released by
+       bs_free_data.
+    */
+    target->refcount = 1;
 
     /* create the tree for file caching */
     ret = iso_rbtree_new(iso_file_src_cmp, &(target->files));
@@ -1923,9 +1945,24 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     pthread_attr_init(&(target->th_attr));
     pthread_attr_setdetachstate(&(target->th_attr), PTHREAD_CREATE_JOINABLE);
 
+    /* To avoid race conditions with the caller, this mark must be set
+       before the thread starts. So the caller can rely on a value of 0
+       really meaning that the write has ended, and not that it might not have
+       begun yet.
+       In normal processing, the value will be changed to 0 at the end of
+       write_function().
+    */
+    target->image->generator_is_running = 1;
+
+
+    /* Claim that target may not get destroyed by bs_free_data() before
+       write_function() is done with it */
+    target->refcount++;
+
     ret = pthread_create(&(target->wthread), &(target->th_attr),
                          write_function, (void *) target);
     if (ret != 0) {
+        target->refcount--;
         iso_msg_submit(target->image->id, ISO_THREAD_ERROR, 0,
                       "Cannot create writer thread");
         ret = ISO_THREAD_ERROR;
@@ -1945,6 +1982,7 @@ int ecma119_image_new(IsoImage *src, IsoWriteOpts *opts, Ecma119Image **img)
     target_cleanup: ;
     if(image_checksums_mad) /* No checksums is better than mad checksums */
       iso_image_free_checksums(target->image, 0);
+    target->image->generator_is_running = 0;
     ecma119_image_free(target);
     return ret;
 }
@@ -1995,7 +2033,7 @@ static void bs_free_data(struct burn_source *bs)
                   iso_ring_buffer_get_times_full(target->buffer),
                   iso_ring_buffer_get_times_empty(target->buffer));
 
-    /* now we can safety free target */
+    /* The reference to target was inherited from ecma119_image_new() */
     ecma119_image_free(target);
 }
 

libisofs/ecma119.h

@@ -345,6 +345,8 @@ typedef struct Iso_Image_Writer IsoImageWriter;
 
 struct ecma119_image
 {
+    int refcount;
+
     IsoImage *image;
     Ecma119Node *root;
 

libisofs/image.c

@@ -89,6 +89,7 @@ int iso_image_new(const char *name, IsoImage **image)
     img->checksum_end_lba = 0;
     img->checksum_idx_count = 0;
     img->checksum_array = NULL;
+    img->generator_is_running = 0;
     *image = img;
     return ISO_SUCCESS;
 }
@@ -607,3 +608,8 @@ int iso_image_set_checksums(IsoImage *image, char *checksum_array,
     return 1;
 }
 
+int iso_image_generator_is_running(IsoImage *image)
+{
+    return image->generator_is_running;
+}
+

libisofs/image.h

@@ -166,6 +166,12 @@ struct Iso_Image
     uint32_t checksum_idx_count;
     char *checksum_array;
 
+    /**
+     * Whether a write run has been started by iso_image_create_burn_source()
+     * and has not yet been finished.
+     */
+    int generator_is_running;
+
 };
 
 

libisofs/libisofs.h

@@ -1870,11 +1870,9 @@ int iso_write_opts_set_part_offset(IsoWriteOpts *opts,
  *        The option set to be manipulated.
  * @param libjte_handle
  *        Pointer to a struct libjte_env e.g. created by libjte_new().
- *        It must stay existent from the start of image writing by
+ *        It must stay existent from the start of image generation by
  *        iso_image_create_burn_source() until the write thread has ended.
-
- *    >>> ts B00928 Need a way to inquire run status independent of libburn.
-
+ *        This can be inquired by iso_image_generator_is_running().
  *        In order to keep the libisofs API identical with and without
  *        libjte support the parameter type is (void *).
  * @return
@@ -1940,6 +1938,20 @@ int iso_write_opts_set_tail_blocks(IsoWriteOpts *opts, uint32_t num_blocks);
 int iso_write_opts_get_data_start(IsoWriteOpts *opts, uint32_t *data_start,
                                   int flag);
 
+/**
+ * Update the sizes of all files added to image.
+ *
+ * This may be called just before iso_image_create_burn_source() to force
+ * libisofs to check the file sizes again (they're already checked when added
+ * to IsoImage). It is useful if you have changed some files after adding then
+ * to the image.
+ *
+ * @return
+ *    1 on success, < 0 on error
+ * @since 0.6.8
+ */
+int iso_image_update_sizes(IsoImage *image);
+
 /**
  * Create a burn_source and a thread which immediately begins to generate
  * the image. That burn_source can be used with libburn as a data source
@@ -1966,18 +1978,22 @@ int iso_image_create_burn_source(IsoImage *image, IsoWriteOpts *opts,
                                  struct burn_source **burn_src);
 
 /**
- * Update the sizes of all files added to image.
- *
- * This may be called just before iso_image_create_burn_source() to force
- * libisofs to check the file sizes again (they're already checked when added
- * to IsoImage). It is useful if you have changed some files after adding then
- * to the image.
- *
+ * Inquire whether the image generator thread is still at work. As soon as the
+ * reply is 0, the caller of iso_image_create_burn_source() may assume that
+ * the image generation has ended.
+ * Nevertheless there may still be readily formatted output data pending in
+ * the burn_source or its consumers. So the final delivery of the image has
+ * also to be checked at the data consumer side,e.g. by burn_drive_get_status()
+ * in case of libburn as consumer.
+ * @param image
+ *     The image to inquire.
  * @return
- *    1 on success, < 0 on error
- * @since 0.6.8
+ *     1 generating of image stream is still in progress
+ *     0 generating of image stream has ended meanwhile
+ *
+ * @since 0.6.38
  */
-int iso_image_update_sizes(IsoImage *image);
+int iso_image_generator_is_running(IsoImage *image);
 
 /**
  * Creates an IsoReadOpts for reading an existent image. You should set the

libisofs/libisofs.ver

@@ -80,6 +80,7 @@ iso_image_fs_get_publisher_id;
 iso_image_fs_get_system_id;
 iso_image_fs_get_volset_id;
 iso_image_fs_get_volume_id;
+iso_image_generator_is_running;
 iso_image_get_abstract_file_id;
 iso_image_get_all_boot_imgs;
 iso_image_get_application_id;