Fix for stalled streams (#7801) (#7818)

(cherry picked from commit b11a6a8)

Author: yschimke

okhttp/src/main/kotlin/okhttp3/internal/http2/Http2Stream.kt

@@ -364,7 +364,8 @@ class Http2Stream internal constructor(
 
               val unacknowledgedBytesRead = readBytesTotal - readBytesAcknowledged
               if (errorExceptionToDeliver == null &&
-                  unacknowledgedBytesRead >= connection.okHttpSettings.initialWindowSize / 2) {
+                unacknowledgedBytesRead >= connection.okHttpSettings.initialWindowSize / 2
+              ) {
                 // Flow control: notify the peer that we're ready for more data! Only send a
                 // WINDOW_UPDATE if the stream isn't in error.
                 connection.writeWindowUpdateLater(id, unacknowledgedBytesRead)
@@ -387,8 +388,6 @@ class Http2Stream internal constructor(
         }
 
         if (readBytesDelivered != -1L) {
-          // Update connection.unacknowledgedBytesRead outside the synchronized block.
-          updateConnectionFlowControl(readBytesDelivered)
           return readBytesDelivered
         }
 
@@ -418,41 +417,39 @@ class Http2Stream internal constructor(
     internal fun receive(source: BufferedSource, byteCount: Long) {
       this@Http2Stream.assertThreadDoesntHoldLock()
 
-      var byteCount = byteCount
+      var remainingByteCount = byteCount
 
-      while (byteCount > 0L) {
+      while (remainingByteCount > 0L) {
         val finished: Boolean
         val flowControlError: Boolean
         synchronized(this@Http2Stream) {
           finished = this.finished
-          flowControlError = byteCount + readBuffer.size > maxByteCount
+          flowControlError = remainingByteCount + readBuffer.size > maxByteCount
         }
 
         // If the peer sends more data than we can handle, discard it and close the connection.
         if (flowControlError) {
-          source.skip(byteCount)
+          source.skip(remainingByteCount)
           closeLater(ErrorCode.FLOW_CONTROL_ERROR)
           return
         }
 
         // Discard data received after the stream is finished. It's probably a benign race.
         if (finished) {
-          source.skip(byteCount)
+          source.skip(remainingByteCount)
           return
         }
 
         // Fill the receive buffer without holding any locks.
-        val read = source.read(receiveBuffer, byteCount)
+        val read = source.read(receiveBuffer, remainingByteCount)
         if (read == -1L) throw EOFException()
-        byteCount -= read
+        remainingByteCount -= read
 
         // Move the received data to the read buffer to the reader can read it. If this source has
         // been closed since this read began we must discard the incoming data and tell the
         // connection we've done so.
-        var bytesDiscarded = 0L
         synchronized(this@Http2Stream) {
           if (closed) {
-            bytesDiscarded = receiveBuffer.size
             receiveBuffer.clear()
           } else {
             val wasEmpty = readBuffer.size == 0L
@@ -462,10 +459,13 @@ class Http2Stream internal constructor(
             }
           }
         }
-        if (bytesDiscarded > 0L) {
-          updateConnectionFlowControl(bytesDiscarded)
-        }
       }
+
+      // Update the connection flow control, as this is a shared resource.
+      // Even if our stream doesn't need more data, others might.
+      // But delay updating the stream flow control until that stream has been
+      // consumed
+      updateConnectionFlowControl(byteCount)
     }
 
     override fun timeout(): Timeout = readTimeout