From b58f67aa90ae7fa5e357ebf1b29f1bc1619fabbf Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Fri, 21 Jun 2013 09:35:04 +0100
Subject: [PATCH] single-thread class init
See:
https://github.com/jcupitt/libvips/issues/64
We were seeing races in class init on very-many-core machines. GObject
is supposed to single-thread class init, I think, so this shouldn't
happen. Perhaps class init via g_type_class_ref() is not
single-threaded.
---
libvips/iofuncs/object.c | 22 +++++++++++++++++++---
1 file changed, 19 insertions(+), 3 deletions(-)
diff --git a/libvips/iofuncs/object.c b/libvips/iofuncs/object.c
index 7bc474a6..1bb7980a 100644
--- a/libvips/iofuncs/object.c
+++ b/libvips/iofuncs/object.c
@@ -2314,16 +2314,32 @@ test_name( VipsObjectClass *class, const char *nickname )
VipsObjectClass *
vips_class_find( const char *basename, const char *nickname )
{
+ static GOnce vips_class_find_once = G_ONCE_INIT;
+ static GMutex *vips_class_find_lock = NULL;
+
const char *classname = basename ? basename : "VipsObject";
VipsObjectClass *class;
GType base;
- if( !(base = g_type_from_name( classname )) ||
- !(class = vips_class_map_all( base,
- (VipsClassMapFn) test_name, (void *) nickname )) )
+ if( !(base = g_type_from_name( classname )) )
return( NULL );
+ if( !vips_class_find_lock )
+ vips_class_find_lock = g_once( &vips_class_find_once,
+ (GThreadFunc) vips_g_mutex_new, NULL );
+
+ /* We have to single-thread class lookup. The first time this runs on
+ * a class, the g_type_class_ref() in vips_class_map_all() will
+ * trigger class build and construct the arg table. We musn't have
+ * this run more than once.
+ */
+
+ g_mutex_lock( vips_class_find_lock );
+ class = vips_class_map_all( base,
+ (VipsClassMapFn) test_name, (void *) nickname );
+ g_mutex_unlock( vips_class_find_lock );
+
return( class );
}