From 037ff2f12bd10e526781ca4a1e8b0e453939f2db Mon Sep 17 00:00:00 2001
From: Dave Hylands <dhylands@gmail.com>
Date: Wed, 19 Sep 2012 23:34:07 -0700
Subject: [PATCH] Bug 792682 - GonkHal vibrator code incorrectly uses a weak
 reference. r=qDot

---
 hal/gonk/GonkHal.cpp | 32 ++++++++++++++++++++++----------
 1 file changed, 22 insertions(+), 10 deletions(-)

diff --git a/hal/gonk/GonkHal.cpp b/hal/gonk/GonkHal.cpp
index 9b259a30484c..4c775012685c 100644
--- a/hal/gonk/GonkHal.cpp
+++ b/hal/gonk/GonkHal.cpp
@@ -102,7 +102,6 @@ public:
   VibratorRunnable()
     : mMonitor("VibratorRunnable")
     , mIndex(0)
-    , mShuttingDown(false)
   {
     nsCOMPtr<nsIObserverService> os = services::GetObserverService();
     if (!os) {
@@ -110,8 +109,9 @@ public:
       return;
     }
 
-    os->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, /* weak ref */ true);
+    os->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
   }
+
   NS_DECL_ISUPPORTS
   NS_DECL_NSIRUNNABLE
   NS_DECL_NSIOBSERVER
@@ -120,6 +120,8 @@ public:
   void Vibrate(const nsTArray<uint32_t> &pattern);
   void CancelVibrate();
 
+  static bool ShuttingDown() { return sShuttingDown; }
+
 private:
   Monitor mMonitor;
 
@@ -132,11 +134,15 @@ private:
 
   // Set to true in our shutdown observer.  When this is true, we kill the
   // vibrator thread.
-  bool mShuttingDown;
+  static bool sShuttingDown;
 };
 
 NS_IMPL_THREADSAFE_ISUPPORTS2(VibratorRunnable, nsIRunnable, nsIObserver);
 
+bool VibratorRunnable::sShuttingDown = false;
+
+static nsRefPtr<VibratorRunnable> sVibratorRunnable;
+
 NS_IMETHODIMP
 VibratorRunnable::Run()
 {
@@ -151,7 +157,7 @@ VibratorRunnable::Run()
   // condvar onto another thread.  Better just to be chill about small errors in
   // the timing here.
 
-  while (!mShuttingDown) {
+  while (!sShuttingDown) {
     if (mIndex < mPattern.Length()) {
       uint32_t duration = mPattern[mIndex];
       if (mIndex % 2 == 0) {
@@ -164,7 +170,7 @@ VibratorRunnable::Run()
       mMonitor.Wait();
     }
   }
-
+  sVibratorRunnable = NULL;
   return NS_OK;
 }
 
@@ -174,8 +180,9 @@ VibratorRunnable::Observe(nsISupports *subject, const char *topic,
 {
   MOZ_ASSERT(strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) == 0);
   MonitorAutoLock lock(mMonitor);
-  mShuttingDown = true;
+  sShuttingDown = true;
   mMonitor.Notify();
+
   return NS_OK;
 }
 
@@ -198,8 +205,6 @@ VibratorRunnable::CancelVibrate()
   mMonitor.Notify();
 }
 
-VibratorRunnable *sVibratorRunnable = NULL;
-
 void
 EnsureVibratorThreadInitialized()
 {
@@ -207,8 +212,7 @@ EnsureVibratorThreadInitialized()
     return;
   }
 
-  nsRefPtr<VibratorRunnable> runnable = new VibratorRunnable();
-  sVibratorRunnable = runnable;
+  sVibratorRunnable = new VibratorRunnable();
   nsCOMPtr<nsIThread> thread;
   NS_NewThread(getter_AddRefs(thread), sVibratorRunnable);
 }
@@ -218,6 +222,10 @@ EnsureVibratorThreadInitialized()
 void
 Vibrate(const nsTArray<uint32_t> &pattern, const hal::WindowIdentifier &)
 {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (VibratorRunnable::ShuttingDown()) {
+    return;
+  }
   EnsureVibratorThreadInitialized();
   sVibratorRunnable->Vibrate(pattern);
 }
@@ -225,6 +233,10 @@ Vibrate(const nsTArray<uint32_t> &pattern, const hal::WindowIdentifier &)
 void
 CancelVibrate(const hal::WindowIdentifier &)
 {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (VibratorRunnable::ShuttingDown()) {
+    return;
+  }
   EnsureVibratorThreadInitialized();
   sVibratorRunnable->CancelVibrate();
 }