Revert "free main-thread pixel buffers"

This reverts commit 2a77301033.

ChangeLog

@@ -14,8 +14,6 @@
 - tiffsave converts for jpg if jpg compression is turned on
 - tiffsave supports --strip
 - conversions to GREY16 could lock
-- main-thread pixel buffers are freed on image close, improving cache
-  behaviour
 
 18/5/16 started 8.3.2
 - more robust vips image reading

TODO

@@ -1,3 +1,26 @@
+- we free buffers on vips__buffer_shutdown(), called from thread shutdown,
+  but this won't happen for the main thread until program exit!
+
+  therefore any buffers allocated on the main thread will never leave cache,
+  and will eventually take over, forcing all operations out
+
+  we need to free buffers on image close, not thread exit
+
+  structure:
+
+	thread private ->
+		VipsBufferThread * -> hash(im) -> 
+			VipsBufferCache * -> 
+				array of VipsBuffer
+
+  we currently free VipsBufferThread on thread exit, instead we must free
+  VipsBufferCache on image close
+
+  alternative: keep the current thing, but keep a special note of the main 
+  thread VipsBufferCache ... on image close, remove any buffers just from that 
+
+  we'd need vips__thread_main to track the thread that called VIPS_INIT
+
 - add more webp tests to py suite
 
 - try moving some more of the CLI tests to py

libvips/include/vips/internal.h

@@ -102,8 +102,6 @@ extern char *vips__cache_max_files;
 extern gboolean vips__cache_dump;
 extern gboolean vips__cache_trace;
 
-extern GThread *vips__thread_main;
-
 void vips__cache_init( void );
 
 void vips__print_renders( void );

libvips/iofuncs/buffer.c

@@ -20,8 +20,6 @@
  * 18/12/13
  * 	- keep a few buffers in reserve per image, stops malloc/free 
  * 	  cycling when sharing is repeatedly discovered
- * 5/6/16
- * 	- free main thread buffers on image close
  */
 
 /*
@@ -216,16 +214,6 @@ buffer_cache_free( VipsBufferCache *cache )
 	g_free( cache );
 }
 
-static void
-buffer_cache_image_close_cb( VipsObject *object, void *data )
-{
-	VipsImage *im = VIPS_IMAGE( object ); 
-	VipsBufferCache *cache = (VipsBufferCache *) data;
-	VipsBufferThread *buffer_thread = cache->buffer_thread;
-
-	g_hash_table_remove( buffer_thread->hash, im );
-}
-
 static VipsBufferCache *
 buffer_cache_new( VipsBufferThread *buffer_thread, VipsImage *im )
 {
@@ -239,16 +227,6 @@ buffer_cache_new( VipsBufferThread *buffer_thread, VipsImage *im )
 	cache->reserve = NULL;
 	cache->n_reserve = 0;
 
-	/* The buffers on worker threads are freed on thread exit, but buffers
-	 * on the main thread won't be freed until program exit, and will
-	 * eventually fill the cache.
-	 *
-	 * If this is a main-thread buffer, junk it by hand on image close. 
-	 */
-	if( cache->thread == vips__thread_main ) 
-		g_signal_connect( im, "close", 
-			G_CALLBACK( buffer_cache_image_close_cb ), cache ); 
-
 #ifdef DEBUG_CREATE
 	g_mutex_lock( vips__global_lock );
 	vips__buffer_cache_all = 

libvips/iofuncs/init.c

@@ -94,10 +94,6 @@ int vips__fatal = 0;
  */
 GMutex *vips__global_lock = NULL;
 
-/* The thread that called vips_init().
- */
-GThread *vips__thread_main = NULL;
-
 /* Keep a copy of the argv0 here.
  */
 static char *vips__argv0 = NULL;
@@ -144,8 +140,6 @@ vips_get_argv0( void )
  * must not call VIPS_INIT() after vips_shutdown(). In other words, you cannot
  * stop and restart vips. 
  *
- * vips_shutdown() must be called from the same thread that called VIPS_INIT().
- *
  * VIPS_INIT() does approximately the following:
  *
  * + checks that the libvips your program is expecting is 
@@ -160,7 +154,7 @@ vips_get_argv0( void )
  * + creates the main vips types, including #VipsImage and friends
  *
  * + loads any plugins from $libdir/vips-x.y/, where x and y are the
- *   major and minor version numbers for this VIPS
+ *   major and minor version numbers for this VIPS.
  *
  * + if your platform supports atexit(), VIPS_INIT() will ask for
  *   vips_shutdown() to be called on program exit
@@ -400,11 +394,6 @@ vips_init( const char *argv0 )
 	 */
 	vips_vector_init();
 
-	/* The main thread is never shut down, so we need to free some main
-	 * thread resources by hand. Track the maiin thread here. 
-	 */
-	vips__thread_main = g_thread_self();
-
 #ifdef HAVE_GSF
 	/* Use this for structured file write.
 	 */
@@ -517,8 +506,6 @@ vips_thread_shutdown( void )
  * You may call VIPS_INIT() many times and vips_shutdown() many times, but you 
  * must not call VIPS_INIT() after vips_shutdown(). In other words, you cannot
  * stop and restart vips. 
- *
- * vips_shutdown() must be called from the same thread that called VIPS_INIT().
  */
 void
 vips_shutdown( void )
@@ -527,10 +514,6 @@ vips_shutdown( void )
 	printf( "vips_shutdown:\n" );
 #endif /*DEBUG*/
 
-	/* Must be called by the main thread.
-	 */
-	g_assert( vips__thread_main == g_thread_self() );
-
 	vips_cache_drop_all();
 
 	im_close_plugins();