Bug 1267297 - Use AutoEntryScript for script activity bookkeeping instead of the request machinery. r=bholley

Differential Revision: https://phabricator.services.mozilla.com/D4085

--HG--
extra : moz-landing-system : lando

dom/script/ScriptSettings.cpp

@@ -662,8 +662,11 @@ AutoEntryScript::AutoEntryScript(nsIGlobalObject* aGlobalObject,
 {
   MOZ_ASSERT(aGlobalObject);
 
-  if (aIsMainThread && gRunToCompletionListeners > 0) {
-    mDocShellEntryMonitor.emplace(cx(), aReason);
+  if (aIsMainThread) {
+    if (gRunToCompletionListeners > 0) {
+      mDocShellEntryMonitor.emplace(cx(), aReason);
+    }
+    mScriptActivity.emplace(true);
   }
 }
 
@@ -815,11 +818,12 @@ AutoSafeJSContext::AutoSafeJSContext(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMP
 }
 
 AutoSlowOperation::AutoSlowOperation(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM_IN_IMPL)
-  : AutoJSAPI()
+  : mIsMainThread(NS_IsMainThread())
 {
   MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-
-  Init();
+  if (mIsMainThread) {
+    mScriptActivity.emplace(true);
+  }
 }
 
 void
@@ -828,8 +832,10 @@ AutoSlowOperation::CheckForInterrupt()
   // For now we support only main thread!
   if (mIsMainThread) {
     // JS_CheckForInterrupt expects us to be in a realm.
-    JSAutoRealm ar(cx(), xpc::UnprivilegedJunkScope());
-    JS_CheckForInterrupt(cx());
+    AutoJSAPI jsapi;
+    if (jsapi.Init(xpc::UnprivilegedJunkScope())) {
+      JS_CheckForInterrupt(jsapi.cx());
+    }
   }
 }
 

dom/script/ScriptSettings.h

@@ -12,6 +12,7 @@
 #include "MainThreadUtils.h"
 #include "nsIGlobalObject.h"
 #include "nsIPrincipal.h"
+#include "xpcpublic.h"
 
 #include "mozilla/Maybe.h"
 
@@ -383,6 +384,7 @@ private:
   friend nsIPrincipal* GetWebIDLCallerPrincipal();
 
   Maybe<DocshellEntryMonitor> mDocShellEntryMonitor;
+  Maybe<xpc::AutoScriptActivity> mScriptActivity;
   JS::AutoHideScriptedCaller mCallerOverride;
 #ifdef MOZ_GECKO_PROFILER
   AutoProfilerLabel mAutoProfilerLabel;
@@ -455,17 +457,21 @@ private:
  * Use AutoSlowOperation when native side calls many JS callbacks in a row
  * and slow script dialog should be activated if too much time is spent going
  * through those callbacks.
- * AutoSlowOperation puts a JSAutoRequest on the stack so that we don't continue
- * to reset the watchdog and CheckForInterrupt can be then used to check whether
- * JS execution should be interrupted.
+ * AutoSlowOperation puts an AutoScriptActivity on the stack so that we don't
+ * continue to reset the watchdog. CheckForInterrupt can then be used to check
+ * whether JS execution should be interrupted.
+ * This class (including CheckForInterrupt) is a no-op when used off the main
+ * thread.
  */
-class MOZ_RAII AutoSlowOperation : public dom::AutoJSAPI
+class MOZ_RAII AutoSlowOperation
 {
 public:
   explicit AutoSlowOperation(MOZ_GUARD_OBJECT_NOTIFIER_ONLY_PARAM);
   void CheckForInterrupt();
 private:
   MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+  bool mIsMainThread;
+  Maybe<xpc::AutoScriptActivity> mScriptActivity;
 };
 
 /**

js/xpconnect/src/XPCJSContext.cpp

@@ -551,28 +551,49 @@ XPCJSContext::GetWatchdogTimestamp(WatchdogTimestampCategory aCategory)
         mWatchdogManager->GetTimestamp(aCategory, lock);
 }
 
-void
-xpc::SimulateActivityCallback(bool aActive)
-{
-    XPCJSContext::ActivityCallback(XPCJSContext::Get(), aActive);
-}
-
 // static
-void
-XPCJSContext::ActivityCallback(void* arg, bool active)
+bool
+XPCJSContext::RecordScriptActivity(bool aActive)
 {
+    MOZ_ASSERT(NS_IsMainThread());
+
+    XPCJSContext* xpccx = XPCJSContext::Get();
+    if (!xpccx) {
+        // mozilla::SpinEventLoopUntil may use AutoScriptActivity(false) after
+        // we destroyed the XPCJSContext.
+        MOZ_ASSERT(!aActive);
+        return false;
+    }
+
+    bool oldValue = xpccx->SetHasScriptActivity(aActive);
+    if (aActive == oldValue) {
+        // Nothing to do.
+        return oldValue;
+    }
+
     // Since the slow script dialog never activates if we are recording or
     // replaying, don't record/replay JS activity notifications.
     if (recordreplay::IsRecordingOrReplaying()) {
-        return;
+        return oldValue;
     }
 
-    if (!active) {
+    if (!aActive) {
         ProcessHangMonitor::ClearHang();
     }
+    xpccx->mWatchdogManager->RecordContextActivity(xpccx, aActive);
 
-    XPCJSContext* self = static_cast<XPCJSContext*>(arg);
-    self->mWatchdogManager->RecordContextActivity(self, active);
+    return oldValue;
+}
+
+AutoScriptActivity::AutoScriptActivity(bool aActive)
+  : mActive(aActive)
+  , mOldValue(XPCJSContext::RecordScriptActivity(aActive))
+{
+}
+
+AutoScriptActivity::~AutoScriptActivity()
+{
+    MOZ_ALWAYS_TRUE(mActive == XPCJSContext::RecordScriptActivity(mOldValue));
 }
 
 // static
@@ -890,8 +911,6 @@ XPCJSContext::~XPCJSContext()
     Preferences::UnregisterCallback(ReloadPrefsCallback, "fuzzing.enabled", this);
 #endif
 
-    js::SetActivityCallback(Context(), nullptr, nullptr);
-
     // Clear any pending exception.  It might be an XPCWrappedJS, and if we try
     // to destroy it later we will crash.
     SetPendingException(nullptr);
@@ -926,6 +945,7 @@ XPCJSContext::XPCJSContext()
    mWatchdogManager(GetWatchdogManager()),
    mSlowScriptSecondHalf(false),
    mTimeoutAccumulated(false),
+   mHasScriptActivity(false),
    mPendingResult(NS_OK),
    mActive(CONTEXT_INACTIVE),
    mLastStateChange(PR_Now())
@@ -1140,7 +1160,6 @@ XPCJSContext::Initialize(XPCJSContext* aPrimaryContext)
 
     PROFILER_SET_JS_CONTEXT(cx);
 
-    js::SetActivityCallback(cx, ActivityCallback, this);
     JS_AddInterruptCallback(cx, InterruptCallback);
 
     if (!aPrimaryContext) {

js/xpconnect/src/XPCShellImpl.cpp

@@ -590,15 +590,21 @@ SetInterruptCallback(JSContext* cx, unsigned argc, Value* vp)
 }
 
 static bool
-SimulateActivityCallback(JSContext* cx, unsigned argc, Value* vp)
+SimulateNoScriptActivity(JSContext* cx, unsigned argc, Value* vp)
 {
     // Sanity-check args.
     JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
-    if (args.length() != 1 || !args[0].isBoolean()) {
-        JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    if (args.length() != 1 || !args[0].isInt32() || args[0].toInt32() < 0) {
+        JS_ReportErrorASCII(cx, "Expected a positive integer argument");
         return false;
     }
-    xpc::SimulateActivityCallback(args[0].toBoolean());
+
+    // This mimics mozilla::SpinEventLoopUntil but instead of spinning the
+    // event loop we sleep, to make sure we don't run script.
+    xpc::AutoScriptActivity asa(false);
+    PR_Sleep(PR_SecondsToInterval(args[0].toInt32()));
+
+    args.rval().setUndefined();
     return true;
 }
 
@@ -665,7 +671,7 @@ static const JSFunctionSpec glob_functions[] = {
     JS_FN("atob",            xpc::Atob,      1,0),
     JS_FN("btoa",            xpc::Btoa,      1,0),
     JS_FN("setInterruptCallback", SetInterruptCallback, 1,0),
-    JS_FN("simulateActivityCallback", SimulateActivityCallback, 1,0),
+    JS_FN("simulateNoScriptActivity", SimulateNoScriptActivity, 1,0),
     JS_FN("registerAppManifest", RegisterAppManifest, 1, 0),
 #ifdef ENABLE_TESTS
     JS_FN("registerXPCTestComponents", RegisterXPCTestComponents, 0, 0),

js/xpconnect/src/xpcprivate.h

@@ -373,7 +373,14 @@ public:
 
     PRTime GetWatchdogTimestamp(WatchdogTimestampCategory aCategory);
 
-    static void ActivityCallback(void* arg, bool active);
+    static bool RecordScriptActivity(bool aActive);
+
+    bool SetHasScriptActivity(bool aActive) {
+        bool oldValue = mHasScriptActivity;
+        mHasScriptActivity = aActive;
+        return oldValue;
+    }
+
     static bool InterruptCallback(JSContext* cx);
 
     // Mapping of often used strings to jsid atoms that live 'forever'.
@@ -461,6 +468,8 @@ private:
     mozilla::TimeDuration mSlowScriptActualWait;
     bool mTimeoutAccumulated;
 
+    bool mHasScriptActivity;
+
     // mPendingResult is used to implement Components.returnCode.  Only really
     // meaningful while calling through XPCWrappedJS.
     nsresult mPendingResult;

js/xpconnect/src/xpcpublic.h

@@ -550,8 +550,14 @@ WindowGlobalOrNull(JSObject* aObj);
 nsGlobalWindowInner*
 CurrentWindowOrNull(JSContext* cx);
 
-void
-SimulateActivityCallback(bool aActive);
+class MOZ_RAII AutoScriptActivity
+{
+    bool mActive;
+    bool mOldValue;
+  public:
+    explicit AutoScriptActivity(bool aActive);
+    ~AutoScriptActivity();
+};
 
 // This function may be used off-main-thread, in which case it is benignly
 // racey.

js/xpconnect/tests/unit/test_watchdog_hibernate.js

@@ -23,13 +23,11 @@ async function testBody() {
   // scheduling, we should never have more than 3 seconds of inactivity without
   // hibernating. To add some padding for automation, we mandate that hibernation
   // must begin between 2 and 5 seconds from now.
-  await new Promise(resolve => {
-    var timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
-    timer.initWithCallback(resolve, 10000, Ci.nsITimer.TYPE_ONE_SHOT);
-    simulateActivityCallback(false);
-  });
 
-  simulateActivityCallback(true);
+  // Sleep for 10 seconds. Note: we don't use nsITimer here because then we may run
+  // arbitrary (idle) events involving script before it fires.
+  simulateNoScriptActivity(10);
+
   busyWait(1000); // Give the watchdog time to wake up on the condvar.
   var stateChange = Cu.getWatchdogTimestamp("ContextStateChange");
   startHibernation = Cu.getWatchdogTimestamp("WatchdogHibernateStart");

xpcom/threads/nsThreadUtils.h

@@ -21,8 +21,10 @@
 #include "nsString.h"
 #include "nsCOMPtr.h"
 #include "nsAutoPtr.h"
+#include "xpcpublic.h"
 #include "mozilla/Atomics.h"
 #include "mozilla/Likely.h"
+#include "mozilla/Maybe.h"
 #include "mozilla/Move.h"
 #include "mozilla/TimeStamp.h"
 #include "mozilla/Tuple.h"
@@ -320,6 +322,14 @@ SpinEventLoopUntil(Pred&& aPredicate, nsIThread* aThread = nullptr)
 {
   nsIThread* thread = aThread ? aThread : NS_GetCurrentThread();
 
+  // From a latency perspective, spinning the event loop is like leaving script
+  // and returning to the event loop. Tell the watchdog we stopped running
+  // script (until we return).
+  mozilla::Maybe<xpc::AutoScriptActivity> asa;
+  if (NS_IsMainThread()) {
+    asa.emplace(false);
+  }
+
   while (!aPredicate()) {
     bool didSomething = NS_ProcessNextEvent(thread, true);