Attachment 134709 Details for Bug 103037 – Fix the race around accessing cairo_image_traps_compositor

[patch] Fix the race around accessing cairo_image_traps_compositor

Fix-the-race-around-accessing-cairoimagetrapscompo.patch (text/plain), 2.65 KB, created by Mikhail Fludkov on 2017-10-06 16:43:58 UTC

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Creator: Mikhail Fludkov

Created: 2017-10-06 16:43:58 UTC

Size: 2.65 KB

patch

obsolete

>From df1973849cc06a821e98457e00e5f78f98263b3a Mon Sep 17 00:00:00 2001
>From: Mikhail Fludkov <misha@pexip.com>
>Date: Fri, 6 Oct 2017 13:47:51 +0200
>Subject: [PATCH] Fix the race around accessing cairo_image_traps_compositor
>
>https://bugs.freedesktop.org/show_bug.cgi?id=103037
>---
> src/cairo-atomic-private.h   | 30 ++++++++++++++++++++++++++++++
> src/cairo-image-compositor.c |  5 ++++-
> 2 files changed, 34 insertions(+), 1 deletion(-)
>
>diff --git a/src/cairo-atomic-private.h b/src/cairo-atomic-private.h
>index 5001290..27f407f 100644
>--- a/src/cairo-atomic-private.h
>+++ b/src/cairo-atomic-private.h
>@@ -45,6 +45,8 @@
> #include "config.h"
> #endif
> 
>+#include <assert.h>
>+
> /* The autoconf on OpenBSD 4.5 produces the malformed constant name
>  * SIZEOF_VOID__ rather than SIZEOF_VOID_P.  Work around that here. */
> #if !defined(SIZEOF_VOID_P) && defined(SIZEOF_VOID__)
>@@ -393,6 +395,34 @@ _cairo_atomic_ptr_cmpxchg_return_old_fallback(void **x, void *oldv, void *newv)
>     (void) ret__; \
> } while (0)
> 
>+typedef struct _cairo_atomic_once cairo_atomic_once_t;
>+struct _cairo_atomic_once {
>+    cairo_atomic_int_t completed;
>+    cairo_atomic_int_t inprogress;
>+};
>+
>+#define CAIRO_ATOMIC_ONCE_INIT {0, 0}
>+
>+static cairo_always_inline cairo_bool_t
>+_cairo_atomic_once_init_enter(cairo_atomic_once_t *once)
>+{
>+    if (likely (once->completed))
>+	return 0;
>+
>+    if (_cairo_atomic_int_cmpxchg(&once->inprogress, 0, 1))
>+	return 1;
>+
>+    while (!_cairo_atomic_int_get(&once->completed)) {}
>+    return 0;
>+}
>+
>+static cairo_always_inline void
>+_cairo_atomic_once_init_leave(cairo_atomic_once_t *once)
>+{
>+    if (unlikely (!_cairo_atomic_int_cmpxchg(&once->completed, 0, 1)))
>+	assert (0 && "incorrect use of _cairo_atomic_once API (completed != FALSE)");
>+}
>+
> CAIRO_END_DECLS
> 
> #endif
>diff --git a/src/cairo-image-compositor.c b/src/cairo-image-compositor.c
>index bfa1e92..d88e941 100644
>--- a/src/cairo-image-compositor.c
>+++ b/src/cairo-image-compositor.c
>@@ -1244,9 +1244,10 @@ check_composite (const cairo_composite_rectangles_t *extents)
> const cairo_compositor_t *
> _cairo_image_traps_compositor_get (void)
> {
>+    static cairo_atomic_once_t once = CAIRO_ATOMIC_ONCE_INIT;
>     static cairo_traps_compositor_t compositor;
> 
>-    if (compositor.base.delegate == NULL) {
>+    if (_cairo_atomic_once_init_enter(&once)) {
> 	_cairo_traps_compositor_init (&compositor,
> 				      &__cairo_no_compositor);
> 	compositor.acquire = acquire;
>@@ -1269,6 +1270,8 @@ _cairo_image_traps_compositor_get (void)
> #endif
> 	compositor.check_composite_glyphs = check_composite_glyphs;
> 	compositor.composite_glyphs = composite_glyphs;
>+
>+	_cairo_atomic_once_init_leave(&once);
>     }
> 
>     return &compositor.base;
>-- 
>2.7.4

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Attachments on bug 103037: 134564 | 134702 | 134709 | 134722

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