Bug 901364 - Implement a replacement operation callback in XPConnect. r=mrbkap

js/xpconnect/src/XPCJSRuntime.cpp

@@ -39,6 +39,7 @@
 #include "mozilla/dom/Element.h"
 #include "mozilla/Attributes.h"
 #include "AccessCheck.h"
+#include "nsGlobalWindow.h"
 
 #include "GeckoProfiler.h"
 #include "nsJSPrincipals.h"
@@ -1228,6 +1229,67 @@ XPCJSRuntime::CTypesActivityCallback(JSContext *cx, js::CTypesActivityType type)
   }
 }
 
+// static
+bool
+XPCJSRuntime::OperationCallback(JSContext *cx)
+{
+    XPCJSRuntime *self = XPCJSRuntime::Get();
+
+    // If this is the first time the operation callback has fired since we last
+    // returned to the event loop, mark the checkpoint.
+    if (self->mSlowScriptCheckpoint.IsNull()) {
+        self->mSlowScriptCheckpoint = TimeStamp::NowLoRes();
+        return true;
+    }
+
+    // This is at least the second operation callback we've received since
+    // returning to the event loop. See how long it's been, and what the limit
+    // is.
+    TimeDuration duration = TimeStamp::NowLoRes() - self->mSlowScriptCheckpoint;
+    bool chrome =
+      nsContentUtils::IsSystemPrincipal(nsContentUtils::GetSubjectPrincipal());
+    const char *prefName = chrome ? "dom.max_chrome_script_run_time"
+                                  : "dom.max_script_run_time";
+    int32_t limit = Preferences::GetInt(prefName, chrome ? 20 : 10);
+
+    // If there's no limit, or we're within the limit, let it go.
+    if (limit == 0 || duration.ToSeconds() < limit)
+        return true;
+
+    //
+    // This has gone on long enough! Time to take action. ;-)
+    //
+
+    // Get the DOM window associated with the running script. If the script is
+    // running in a non-DOM scope, we have to just let it keep running.
+    RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
+    nsCOMPtr<nsPIDOMWindow> win;
+    if (IS_WN_REFLECTOR(global))
+        win = do_QueryWrappedNative(XPCWrappedNative::Get(global));
+    if (!win)
+        return true;
+
+    // Show the prompt to the user, and kill if requested.
+    nsGlobalWindow::SlowScriptResponse response =
+      static_cast<nsGlobalWindow*>(win.get())->ShowSlowScriptDialog();
+    if (response == nsGlobalWindow::KillSlowScript)
+        return false;
+
+    // The user chose to continue the script. Reset the timer, and disable this
+    // machinery with a pref of the user opted out of future slow-script dialogs.
+    self->mSlowScriptCheckpoint = TimeStamp::NowLoRes();
+    if (response == nsGlobalWindow::AlwaysContinueSlowScript)
+        Preferences::SetInt(prefName, 0);
+
+    return true;
+}
+
+bool
+xpc::OperationCallback(JSContext *cx)
+{
+    return XPCJSRuntime::OperationCallback(cx);
+}
+
 size_t
 XPCJSRuntime::SizeOfIncludingThis(MallocSizeOf mallocSizeOf)
 {

js/xpconnect/src/nsXPConnect.cpp

@@ -1182,6 +1182,9 @@ nsXPConnect::AfterProcessNextEvent(nsIThreadInternal *aThread,
         return NS_OK;
     mEventDepth--;
 
+    // Now that we're back to the event loop, reset the slow script checkpoint.
+    mRuntime->OnAfterProcessNextEvent();
+
     // Call cycle collector occasionally.
     MOZ_ASSERT(NS_IsMainThread());
     nsJSContext::MaybePokeCC();

js/xpconnect/src/xpcprivate.h

@@ -827,6 +827,7 @@ public:
     static void ActivityCallback(void *arg, bool active);
     static void CTypesActivityCallback(JSContext *cx,
                                        js::CTypesActivityType type);
+    static bool OperationCallback(JSContext *cx);
 
     size_t SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf);
 
@@ -836,6 +837,7 @@ public:
     void DeleteJunkScope();
 
     PRTime GetWatchdogTimestamp(WatchdogTimestampCategory aCategory);
+    void OnAfterProcessNextEvent() { mSlowScriptCheckpoint = mozilla::TimeStamp(); }
 
 private:
     XPCJSRuntime(); // no implementation
@@ -876,6 +878,8 @@ private:
     JSObject* mJunkScope;
     nsRefPtr<AsyncFreeSnowWhite> mAsyncSnowWhiteFreer;
 
+    mozilla::TimeStamp mSlowScriptCheckpoint;
+
     nsCOMPtr<nsIException>   mPendingException;
     nsCOMPtr<nsIExceptionManager> mExceptionManager;
     bool mExceptionManagerNotAvailable;

js/xpconnect/src/xpcpublic.h

@@ -67,6 +67,10 @@ AllowXBLScope(JSCompartment *c);
 bool
 IsSandboxPrototypeProxy(JSObject *obj);
 
+// XXXbholley - Temporary - goes away in future patches.
+bool
+OperationCallback(JSContext* cx);
+
 } /* namespace xpc */
 
 #define XPCONNECT_GLOBAL_FLAGS                                                \