NuCachedSource2: more fixes for source read hang

- Do not try to read from HTTP source if already disconnecting

- Let NuCachedSource2::readAt() return immediately when disconnecting

Bug: 17613805

Change-Id: Ibca4d3a4288ae9a9e2f5658a4240ace54efeb220
diff --git a/media/libstagefright/NuCachedSource2.cpp b/media/libstagefright/NuCachedSource2.cpp
index be2a873..f469d4d 100644
--- a/media/libstagefright/NuCachedSource2.cpp
+++ b/media/libstagefright/NuCachedSource2.cpp
@@ -254,6 +254,10 @@
             // set mDisconnecting to true, if a fetch returns after
             // this, the source will be marked as EOS.
             mDisconnecting = true;
+
+            // explicitly signal mCondition so that the pending readAt()
+            // will immediately return
+            mCondition.signal();
         }
 
         // explicitly disconnect from the source, to allow any
@@ -325,7 +329,11 @@
 
         Mutex::Autolock autoLock(mLock);
 
-        if (err == ERROR_UNSUPPORTED || err == -EPIPE) {
+        if (mDisconnecting) {
+            mNumRetriesLeft = 0;
+            mFinalStatus = ERROR_END_OF_STREAM;
+            return;
+        } else if (err == ERROR_UNSUPPORTED || err == -EPIPE) {
             // These are errors that are not likely to go away even if we
             // retry, i.e. the server doesn't support range requests or similar.
             mNumRetriesLeft = 0;
@@ -515,10 +523,14 @@
     CHECK(mAsyncResult == NULL);
     msg->post();
 
-    while (mAsyncResult == NULL) {
+    while (mAsyncResult == NULL && !mDisconnecting) {
         mCondition.wait(mLock);
     }
 
+    if (mDisconnecting) {
+        return ERROR_END_OF_STREAM;
+    }
+
     int32_t result;
     CHECK(mAsyncResult->findInt32("result", &result));