Reliably cancel in-progress CryptoResult(Impl) upon shutdown.

Source/platform/exported/WebCryptoResult.cpp

Index: Source/platform/exported/WebCryptoResult.cpp
diff --git a/Source/platform/exported/WebCryptoResult.cpp b/Source/platform/exported/WebCryptoResult.cpp
index d5515064a86e9aa829d129b2828f678f1820fadf..177968387e7ed4b157c859bf8951f7e618d267fa 100644
--- a/Source/platform/exported/WebCryptoResult.cpp
+++ b/Source/platform/exported/WebCryptoResult.cpp
@@ -33,68 +33,122 @@
 
 #include "platform/CryptoResult.h"
 #include "platform/heap/Heap.h"
-#include <string.h>
+#include "wtf/Atomics.h"
 
 namespace blink {
 
 void WebCryptoResult::completeWithError(WebCryptoErrorType errorType, const WebString& errorDetails)
 {
+    if (cancelled())
+        return;
+    ASSERT(m_impl->isOwnerResult(this));
     m_impl->completeWithError(errorType, errorDetails);
-    reset();
+    clear();
 }
 
 void WebCryptoResult::completeWithBuffer(const void* bytes, unsigned bytesSize)
 {
+    if (cancelled())
+        return;
+    ASSERT(m_impl->isOwnerResult(this));
     m_impl->completeWithBuffer(bytes, bytesSize);
-    reset();
+    clear();
 }
 
 void WebCryptoResult::completeWithJson(const char* utf8Data, unsigned length)
 {
+    if (cancelled())
+        return;
+    ASSERT(m_impl->isOwnerResult(this));
     m_impl->completeWithJson(utf8Data, length);
-    reset();
+    clear();
 }
 
 void WebCryptoResult::completeWithBoolean(bool b)
 {
+    if (cancelled())
+        return;
+    ASSERT(m_impl->isOwnerResult(this));
     m_impl->completeWithBoolean(b);
-    reset();
+    clear();
 }
 
 void WebCryptoResult::completeWithKey(const WebCryptoKey& key)
 {
+    if (cancelled())
+        return;
     ASSERT(!key.isNull());
+    ASSERT(m_impl->isOwnerResult(this));
     m_impl->completeWithKey(key);
-    reset();
+    clear();
 }
 
 void WebCryptoResult::completeWithKeyPair(const WebCryptoKey& publicKey, const WebCryptoKey& privateKey)
 {
+    if (cancelled())
+        return;
     ASSERT(!publicKey.isNull());
     ASSERT(!privateKey.isNull());
+    ASSERT(m_impl->isOwnerResult(this));
     m_impl->completeWithKeyPair(publicKey, privateKey);
-    reset();
+    clear();
 }
 
 bool WebCryptoResult::cancelled() const
 {
-    return m_impl->cancelled();
+    return acquireLoad(&m_cancelled);
 }
 
 WebCryptoResult::WebCryptoResult(const PassRefPtrWillBeRawPtr<CryptoResult>& impl)
-    : m_impl(impl)
+    : m_cancelled(0)
+    , m_impl(impl)
 {
     ASSERT(m_impl.get());
+    bool cancel = m_impl->registerResult(this);
+    // The Blink origin thread invokes this constructor; cancellation
+    // cannot happen while doing so.
+    ASSERT_UNUSED(cancel, !cancel && !cancelled());
 }
 
 void WebCryptoResult::reset()
 {
-    m_impl.reset();
+    CryptoResult* result = m_impl.get();
+    if (cancelled())
+        return;
+
+    if (result) {
+        result->unregisterResult(this);
+        m_impl.reset();
+    }
+}
+
+void WebCryptoResult::clear()
+{
+    reset();
+    releaseStore(&m_cancelled, 1);
 }
 
 void WebCryptoResult::assign(const WebCryptoResult& o)
 {
     m_impl = o.m_impl;
+    m_cancelled = o.cancelled();
+    if (m_cancelled) {
+        m_impl.reset();
+        return;
+    }
+
+    // Notice that m_impl will not be updated by the Blink thread calling cancel()
+    // until registerResult(this) has been called for it.
+    //
+    // Should the o.m_impl CryptoResultImpl be concurrently cancelled, clear out the
+    // WebCryptoResult that was attempted registered, effectively forwarding the
+    // cancellation to the assigned result.
+    if (!m_impl.isNull()) {
+        bool cancel = m_impl->registerResult(this);
+        releaseStore(&m_cancelled, cancel);
+        if (cancel)
+            m_impl.reset();
+    }
 }
 
 } // namespace blink