[PATCH] [cairo-atomic] Introduce atomic ops.
Chris Wilson
chris at chris-wilson.co.uk
Fri Sep 21 02:45:55 PDT 2007
Test for the availability of the Intel __sync_* atomic primitives and
use them to define a couple of operations useful for reference counting.
If the atomic primitives are not available, use a mutex locked variant.
If the contention on that mutex is too high, then we can in the future
use an array of mutexes using the address of the atomic variable as the
hash.
---
configure.in | 3 ++
src/Makefile.am | 2 +
src/cairo-atomic-private.h | 58 +++++++++++++++++++++++++++++++++++++++
src/cairo-atomic.c | 59 ++++++++++++++++++++++++++++++++++++++++
src/cairo-mutex-list-private.h | 3 ++
5 files changed, 125 insertions(+), 0 deletions(-)
diff --git a/configure.in b/configure.in
index aa7c1e7..e9bbfe8 100644
--- a/configure.in
+++ b/configure.in
@@ -89,6 +89,9 @@ dnl ===========================================================================
AC_CHECK_FUNCS(vasnprintf)
+AC_TRY_COMPILE([int atomic_add(int i) { return __sync_fetch_and_add (&i, 1); }], [],
+ AC_DEFINE(CAIRO_HAS_ATOMIC_OPS, 1, [Enable if your compiler supports the Intel __sync_* atomic primitives]))
+
AC_CHECK_LIBM
LIBS="$LIBS $LIBM"
diff --git a/src/Makefile.am b/src/Makefile.am
index ae7cb63..189ccea 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -172,6 +172,8 @@ libcairo_la_base_sources = \
cairo-arc.c \
cairo-arc-private.h \
cairo-array.c \
+ cairo-atomic.c \
+ cairo-atomic-private.h \
cairo-base85-stream.c \
cairo-bentley-ottmann.c \
cairo-cache.c \
diff --git a/src/cairo-atomic-private.h b/src/cairo-atomic-private.h
new file mode 100644
index 0000000..038d97f
--- /dev/null
+++ b/src/cairo-atomic-private.h
@@ -0,0 +1,58 @@
+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2007 Chris Wilson
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * The Initial Developer of the Original Code is University of Southern
+ * California.
+ *
+ * Contributor(s):
+ * Chris Wilson <chris at chris-wilson.co.uk>
+ */
+
+#ifndef CAIRO_ATOMIC_PRIVATE_H
+#define CAIRO_ATOMIC_PRIVATE_H
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+CAIRO_BEGIN_DECLS
+
+#if CAIRO_HAS_ATOMIC_OPS
+#define _cairo_atomic_inc(x) __sync_fetch_and_add(x, 1)
+#define _cairo_atomic_dec_and_test(x) (__sync_fetch_and_add(x, -1) == 1)
+#else
+cairo_private void
+_cairo_atomic_inc (int *x);
+cairo_private cairo_bool_t
+_cairo_atomic_dec_and_test (int *x);
+#endif
+
+CAIRO_END_DECLS
+
+#endif
diff --git a/src/cairo-atomic.c b/src/cairo-atomic.c
new file mode 100644
index 0000000..2e65578
--- /dev/null
+++ b/src/cairo-atomic.c
@@ -0,0 +1,59 @@
+/* cairo - a vector graphics library with display and print output
+ *
+ * Copyright © 2007 Chris Wilson
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it either under the terms of the GNU Lesser General Public
+ * License version 2.1 as published by the Free Software Foundation
+ * (the "LGPL") or, at your option, under the terms of the Mozilla
+ * Public License Version 1.1 (the "MPL"). If you do not alter this
+ * notice, a recipient may use your version of this file under either
+ * the MPL or the LGPL.
+ *
+ * You should have received a copy of the LGPL along with this library
+ * in the file COPYING-LGPL-2.1; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * You should have received a copy of the MPL along with this library
+ * in the file COPYING-MPL-1.1
+ *
+ * The contents of this file are subject to the Mozilla Public License
+ * Version 1.1 (the "License"); you may not use this file except in
+ * compliance with the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
+ * OF ANY KIND, either express or implied. See the LGPL or the MPL for
+ * the specific language governing rights and limitations.
+ *
+ * The Original Code is the cairo graphics library.
+ *
+ * Contributor(s):
+ * Chris Wilson <chris at chris-wilson.co.uk>
+ */
+
+#include "cairoint.h"
+
+#include "cairo-atomic-private.h"
+#include "cairo-mutex-private.h"
+
+#ifndef CAIRO_HAS_ATOMIC_OPS
+void
+_cairo_atomic_inc (int *x)
+{
+ CAIRO_MUTEX_LOCK (_cairo_atomic_mutex);
+ *x += 1;
+ CAIRO_MUTEX_UNLOCK (_cairo_atomic_mutex);
+}
+
+cairo_bool_t
+_cairo_atomic_dec_and_test (int *x)
+{
+ cairo_bool_t ret;
+
+ CAIRO_MUTEX_LOCK (_cairo_atomic_mutex);
+ ret = --*x == 0;
+ CAIRO_MUTEX_UNLOCK (_cairo_atomic_mutex);
+
+ return ret;
+}
+#endif
diff --git a/src/cairo-mutex-list-private.h b/src/cairo-mutex-list-private.h
index abb4a9a..9960797 100644
--- a/src/cairo-mutex-list-private.h
+++ b/src/cairo-mutex-list-private.h
@@ -46,6 +46,9 @@ CAIRO_MUTEX_DECLARE (_cairo_ft_unscaled_font_map_mutex);
CAIRO_MUTEX_DECLARE (_cairo_xlib_display_mutex);
#endif
+#ifndef CAIRO_HAS_ATOMIC_OPS
+CAIRO_MUTEX_DECLARE (_cairo_atomic_mutex);
+#endif
/* Undefine, to err on unintended inclusion */
#undef CAIRO_MUTEX_DECLARE
--
1.4.4.2
--dWYAkE0V1FpFQHQ3
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