Changeset 275500 in webkit

Timestamp:

Apr 6, 2021 2:59:36 AM (3 years ago)

Author:

Chris Lord

Message:

BidiContext caching is not thread-safe
​https://bugs.webkit.org/show_bug.cgi?id=224179

Reviewed by Darin Adler.

Make BidiContext ThreadSafeRefCounted and make shared context creation
thread-safe. This is needed by OffscreenCanvas to use text in Workers.

No new tests, covered by existing tests.

• platform/text/BidiContext.cpp:

(WebCore::BidiContext::create):

• platform/text/BidiContext.h:

Location:

trunk/Source/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/text/BidiContext.cpp (modified) (2 diffs)
• platform/text/BidiContext.h (modified) (2 diffs)

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2021-04-06  Chris Lord  <clord@igalia.com>
+
+        BidiContext caching is not thread-safe
+        https://bugs.webkit.org/show_bug.cgi?id=224179
+
+        Reviewed by Darin Adler.
+
+        Make BidiContext ThreadSafeRefCounted and make shared context creation
+        thread-safe. This is needed by OffscreenCanvas to use text in Workers.
+
+        No new tests, covered by existing tests.
+
+        * platform/text/BidiContext.cpp:
+        (WebCore::BidiContext::create):
+        * platform/text/BidiContext.h:
+
 2021-04-06  Frédéric Wang  <fwang@igalia.com>
 

trunk/Source/WebCore/platform/text/BidiContext.cpp

@@ -27 +27 @@
 namespace WebCore {
 
-struct SameSizeAsBidiContext : public RefCounted<SameSizeAsBidiContext> {
+struct SameSizeAsBidiContext : public ThreadSafeRefCounted<SameSizeAsBidiContext> {
     uint32_t bitfields : 16;
     void* parent;
@@ -58 +58 @@
     if (!level) {
         if (!override) {
-            static BidiContext& ltrContext = createUncached(0, U_LEFT_TO_RIGHT, false, FromStyleOrDOM, 0).leakRef();
-            return ltrContext;
+            static NeverDestroyed<RefPtr<BidiContext>> ltrContext;
+            static std::once_flag ltrContextOnceFlag;
+            std::call_once(ltrContextOnceFlag, [&]() {
+                ltrContext.get() = createUncached(0, U_LEFT_TO_RIGHT, false, FromStyleOrDOM, 0);
+            });
+            return *ltrContext.get();
         }
 
-        static BidiContext& ltrOverrideContext = createUncached(0, U_LEFT_TO_RIGHT, true, FromStyleOrDOM, 0).leakRef();
-        return ltrOverrideContext;
+        static NeverDestroyed<RefPtr<BidiContext>> ltrOverrideContext;
+        static std::once_flag ltrOverrideContextOnceFlag;
+        std::call_once(ltrOverrideContextOnceFlag, [&]() {
+            ltrOverrideContext.get() = createUncached(0, U_LEFT_TO_RIGHT, true, FromStyleOrDOM, 0);
+        });
+        return *ltrOverrideContext.get();
     }
 
     if (!override) {
-        static BidiContext& rtlContext = createUncached(1, U_RIGHT_TO_LEFT, false, FromStyleOrDOM, 0).leakRef();
-        return rtlContext;
+        static NeverDestroyed<RefPtr<BidiContext>> rtlContext;
+        static std::once_flag rtlContextOnceFlag;
+        std::call_once(rtlContextOnceFlag, [&]() {
+            rtlContext.get() = createUncached(1, U_RIGHT_TO_LEFT, false, FromStyleOrDOM, 0);
+        });
+        return *rtlContext.get();
     }
 
-    static BidiContext& rtlOverrideContext = createUncached(1, U_RIGHT_TO_LEFT, true, FromStyleOrDOM, 0).leakRef();
-    return rtlOverrideContext;
+    static NeverDestroyed<RefPtr<BidiContext>> rtlOverrideContext;
+    static std::once_flag rtlOverrideContextOnceFlag;
+    std::call_once(rtlOverrideContextOnceFlag, [&]() {
+        rtlOverrideContext.get() = createUncached(1, U_RIGHT_TO_LEFT, true, FromStyleOrDOM, 0);
+    });
+    return *rtlOverrideContext.get();
 }
 

trunk/Source/WebCore/platform/text/BidiContext.h

@@ -23 +23 @@
 
 #include <unicode/uchar.h>
-#include <wtf/RefCounted.h>
 #include <wtf/RefPtr.h>
+#include <wtf/ThreadSafeRefCounted.h>
 
 namespace WebCore {
@@ -31 +31 @@
 
 // Used to keep track of explicit embeddings.
-class BidiContext : public RefCounted<BidiContext> {
+class BidiContext : public ThreadSafeRefCounted<BidiContext> {
 public:
     WEBCORE_EXPORT static Ref<BidiContext> create(unsigned char level, UCharDirection, bool override = false, BidiEmbeddingSource = FromStyleOrDOM, BidiContext* parent = nullptr);