libvips · jcupitt · Jul 11, 2025 · Jul 6, 2025 · Jul 8, 2025 · Jul 11, 2025
diff --git a/ChangeLog b/ChangeLog
@@ -3,6 +3,7 @@ master
 - add dcrawload, dcrawload_source, dcrawload_buffer: load raw camera files
   using libraw [lxsameer]
 - add magickload_source: load from a source with imagemagick
+- add vips__worker_exit(): enables fast threadpool shutdown
 - larger mmap windows on 64-bit machines improve random access mode for many
   file formats
 

diff --git a/libvips/conversion/subsample.c b/libvips/conversion/subsample.c
@@ -53,6 +53,7 @@
 #include <stdlib.h>
 
 #include <vips/vips.h>
+#include <vips/internal.h>
 
 #include "pconversion.h"
 
@@ -102,7 +103,10 @@ vips_subsample_line_gen(VipsRegion *out_region,
 		VipsPel *q = VIPS_REGION_ADDR(out_region, le, y);
 		VipsPel *p;
 
-		/* Loop across the region, in owidth sized pieces.
+		if (vips__worker_exit())
+			return 0;
+
+		/* Loop across the region, in owidth-sized pieces.
 		 */
 		for (x = le; x < ri; x += owidth) {
 			/* How many pixels do we make this time?
@@ -165,20 +169,17 @@ vips_subsample_point_gen(VipsRegion *out_region,
 		VipsPel *q = VIPS_REGION_ADDR(out_region, le, y);
 		VipsPel *p;
 
-		/* Loop across the region, in owidth sized pieces.
-		 */
+		if (vips__worker_exit())
+			return 0;
+
 		for (x = le; x < ri; x++) {
-			/* Ask for input.
-			 */
 			s.left = x * subsample->xfac;
 			s.top = y * subsample->yfac;
 			s.width = 1;
 			s.height = 1;
 			if (vips_region_prepare(ir, &s))
 				return -1;
 
-			/* Append new pels to output.
-			 */
 			p = VIPS_REGION_ADDR(ir, s.left, s.top);
 			for (k = 0; k < ps; k++)
 				q[k] = p[k];

diff --git a/libvips/include/vips/internal.h b/libvips/include/vips/internal.h
@@ -166,6 +166,7 @@ void vips_threadset_free(VipsThreadset *set);
 
 VIPS_API void vips__worker_lock(GMutex *mutex);
 VIPS_API void vips__worker_cond_wait(GCond *cond, GMutex *mutex);
+gboolean vips__worker_exit(void);
 
 void vips__cache_init(void);
 

diff --git a/libvips/include/vips/threadpool.h b/libvips/include/vips/threadpool.h
@@ -96,7 +96,6 @@ typedef struct _VipsThreadState {
 	 * debugging race conditions.
 	 */
 	gboolean stall;
-
 } VipsThreadState;
 
 typedef struct _VipsThreadStateClass {

diff --git a/libvips/iofuncs/sinkscreen.c b/libvips/iofuncs/sinkscreen.c
@@ -1,3 +1,3 @@
 /* asynchronous screen sink
 *
 * 1/1/10
@@ -115,10 +115,10 @@
 
 	/* Parameters.
 	 */
-	VipsImage *in;	 /* Image we render */
-	VipsImage *out;	 /* Write tiles here on demand */
-	VipsImage *mask; /* Set valid pixels here */
-	int tile_width;	 /* Tile size */
+	VipsImage *in;			/* Image we render */
+	VipsImage *out;			/* Write tiles here on demand */
+	VipsImage *mask;		/* Set valid pixels here */
+	int tile_width;			/* Tile size */
 	int tile_height;
 	int max_tiles;		   /* Maximum number of tiles */
 	int priority;		   /* Larger numbers done sooner */
@@ -139,9 +139,9 @@
 
 	/* Tile cache.
 	 */
-	GSList *all; /* All our tiles */
-	int ntiles;	 /* Number of tiles */
-	int ticks;	 /* Inc. on each access ... used for LRU */
+	GSList *all;			/* All our tiles */
+	int ntiles;				/* Number of tiles */
+	int ticks;				/* Inc. on each access ... used for LRU */
 
 	/* List of dirty tiles. Most recent at the front.
 	 */
@@ -194,6 +194,18 @@
  */
 static gboolean render_reschedule = FALSE;
 
+/* Set this GPrivate to link a thread back to its Render struct.
+ */
+static GPrivate render_worker_key;
+
+gboolean
+vips__worker_exit(void)
+{
+	Render *render = (Render *) g_private_get(&render_worker_key);
+
+	return render && render->shutdown;
+}
+
 static void
 render_thread_state_class_init(RenderThreadStateClass *class)
 {
@@ -269,6 +281,7 @@
 
 #ifdef VIPS_DEBUG_AMBER
 	render_num_renders -= 1;
+	printf("%d active renders\n", render_num_renders);
 #endif /*VIPS_DEBUG_AMBER*/
 
 	return 0;
@@ -295,7 +308,7 @@
 static int
 render_unref(Render *render)
 {
-	int kill;
+	gboolean kill;
 
 #if GLIB_CHECK_VERSION(2, 58, 0)
 	g_assert(!g_atomic_ref_count_compare(&render->ref_count, 0));
@@ -426,10 +439,16 @@
 	VIPS_DEBUG_MSG("calculating tile %p %dx%d\n",
 		tile, tile->area.left, tile->area.top);
 
+	/* vips__worker_exit() uses this to find the render to check for
+	 * shutdown.
+	 */
+	g_private_set(&render_worker_key, render);
+
 	if (vips_region_prepare_to(state->reg, tile->region,
 			&tile->area, tile->area.left, tile->area.top)) {
 		VIPS_DEBUG_MSG_RED("render_work: vips_region_prepare_to() failed: %s\n",
 			vips_error_buffer());
+		g_private_set(&render_worker_key, NULL);
 		return -1;
 	}
 	tile->painted = TRUE;
@@ -438,6 +457,8 @@
 		render->notify)
 		render->notify(render->out, &tile->area, render->a);
 
+	g_private_set(&render_worker_key, NULL);
+
 	return 0;
 }
 
@@ -620,6 +641,7 @@
 
 #ifdef VIPS_DEBUG_AMBER
 	render_num_renders += 1;
+	printf("%d active renders\n", render_num_renders);
 #endif /*VIPS_DEBUG_AMBER*/
 
 	return render;
@@ -1094,6 +1116,11 @@
 
 	Render *render = (Render *) data;
 
+	/* vips__worker_exit() uses this to find the render to check for
+	 * shutdown.
+	 */
+	g_private_set(&render_worker_key, render);
+
 	// this will quit on ->shutdown == TRUE
 	if (vips_threadpool_run(render->in,
 			render_thread_state_new,
@@ -1103,6 +1130,8 @@
 			render))
 		VIPS_DEBUG_MSG_RED("render_work_private: threadpool_run failed\n");
 
+	g_private_set(&render_worker_key, NULL);
+
 	render_unref(render);
 
 	VIPS_DEBUG_MSG_AMBER("render_work_private: stop\n");
@@ -1144,11 +1173,11 @@
  * uchar image and has 255 for pixels which are currently in cache and 0
  * for uncalculated pixels.
  *
- * Renders with a positive priority are assumed to be large, gh-priority,
+ * Renders with a positive priority are assumed to be large, high-priority,
  * foreground images. Although there can be many of these, only one is ever
  * active, to avoid overcommitting threads.
  *
- * Renders with a negative priority are assumed to be small, thumbnail images
+ * Renders with a negative priority are assumed to be small, thumbnail images,
  * consisting of a single tile. Single tile images are effectively
  * single-threaded, so all these renders are evaluated together.
  *

diff --git a/libvips/iofuncs/threadpool.c b/libvips/iofuncs/threadpool.c
@@ -379,8 +379,6 @@ vips_thread_main_loop(void *a, void *b)
 	VipsWorker *worker = (VipsWorker *) a;
 	VipsThreadpool *pool = worker->pool;
 
-	g_assert(pool == worker->pool);
-
 	VIPS_GATE_START("vips_thread_main_loop: thread");
 
 	g_private_set(&worker_key, worker);
@@ -481,9 +479,6 @@ vips_threadpool_wait(VipsThreadpool *pool)
 static void
 vips_threadpool_free(VipsThreadpool *pool)
 {
-	VIPS_DEBUG_MSG("vips_threadpool_free: \"%s\" (%p)\n",
-		pool->im->filename, pool);
-
 	vips_threadpool_wait(pool);
 
 	g_mutex_clear(&pool->allocate_lock);
@@ -532,9 +527,6 @@ vips_threadpool_new(VipsImage *im)
 	 */
 	pool->max_workers = vips_image_get_concurrency(im, pool->max_workers);
 
-	VIPS_DEBUG_MSG("vips_threadpool_new: \"%s\" (%p), with %d threads\n",
-		im->filename, pool, pool->max_workers);
-
 	return pool;
 }