Revert "servlet: fix write when not ready in AsyncServletOutputStreamWriter (#12867)

This reverts commit 243b79e. The
approach taken of ensuring subsequent writes go through the container
thread via onWritePossible() hasn't eliminated the need for catching the
IllegalStateException (which you are catching and buffering the write if
it happens). We have observed that the UndertowInteropTest now hangs
instead of the earlier flaky failures due to uncaught exception. There
has been another PR #12732 for the
same issue that explicitly checks isReady.getAsBoolean() in addition to
the cached state, that's probably most reliable, because you don't have
to deal with callback scheduling and the state changing in the meantime.
We would like to proceed with that PR and revert this one.

@mgustimz

Author: kannanjgithub

servlet/src/main/java/io/grpc/servlet/AsyncServletOutputStreamWriter.java

@@ -218,15 +218,7 @@ private void assureReadyAndDrainedTurnsFalse() {
   private void runOrBuffer(ActionItem actionItem) throws IOException {
     WriteState curState = writeState.get();
     if (curState.readyAndDrained) { // write to the outputStream directly
-      try {
-        actionItem.run();
-      } catch (IllegalStateException e) {
-        if (actionItem == flushAction || actionItem == completeAction) {
-          throw e;
-        }
-        buffer(actionItem, curState);
-        return;
-      }
+      actionItem.run();
       if (actionItem == completeAction) {
         return;
       }
@@ -238,26 +230,20 @@ private void runOrBuffer(ActionItem actionItem) throws IOException {
         log.finest("the servlet output stream becomes not ready");
       }
     } else { // buffer to the writeChain
-      buffer(actionItem, curState);
+      writeChain.offer(actionItem);
+      if (!writeState.compareAndSet(curState, curState.withReadyAndDrained(false))) {
+        checkState(
+            writeState.get().readyAndDrained,
+            "Bug: onWritePossible() should have changed readyAndDrained to true, but not");
+        ActionItem lastItem = writeChain.poll();
+        if (lastItem != null) {
+          checkState(lastItem == actionItem, "Bug: lastItem != actionItem");
+          runOrBuffer(lastItem);
+        }
+      } // state has not changed since
     }
   }
 
-  private void buffer(ActionItem actionItem, WriteState curState) throws IOException {
-    writeChain.offer(actionItem);
-    if (writeState.compareAndSet(curState, curState.withReadyAndDrained(false))) {
-      LockSupport.unpark(parkingThread);
-    } else {
-      checkState(
-          writeState.get().readyAndDrained,
-          "Bug: onWritePossible() should have changed readyAndDrained to true, but not");
-      ActionItem lastItem = writeChain.poll();
-      if (lastItem != null) {
-        checkState(lastItem == actionItem, "Bug: lastItem != actionItem");
-        runOrBuffer(lastItem);
-      }
-    } // state has not changed since
-  }
-
   /** Write actions, e.g. writeBytes, flush, complete. */
   @FunctionalInterface
   @VisibleForTesting