diff --git a/includes/MediaWiki.php b/includes/MediaWiki.php
index 5c975142bd6..19614d11d29 100644
--- a/includes/MediaWiki.php
+++ b/includes/MediaWiki.php
@@ -634,11 +634,10 @@ class MediaWiki {
 
 	/**
 	 * @see MediaWiki::preOutputCommit()
-	 * @param callable|null $postCommitWork [default: null]
 	 * @since 1.26
 	 */
-	public function doPreOutputCommit( callable $postCommitWork = null ) {
-		self::preOutputCommit( $this->context, $postCommitWork );
+	private function doPreOutputCommit() {
+		self::preOutputCommit( $this->context );
 	}
 
 	/**
@@ -649,11 +648,11 @@ class MediaWiki {
 	 * If there is a significant amount of content to flush, it can be done in $postCommitWork
 	 *
 	 * @param IContextSource $context
-	 * @param callable|null $postCommitWork [default: null]
+	 * @param callable|null $postCommitWork Unused as of MediaWiki 1.39
 	 * @since 1.27
 	 */
 	public static function preOutputCommit(
-		IContextSource $context, callable $postCommitWork = null
+		IContextSource $context, $postCommitWork = null
 	) {
 		$config = $context->getConfig();
 		$request = $context->getRequest();
@@ -702,7 +701,7 @@ class MediaWiki {
 		$cpClientId = null;
 		$lbFactory->shutdown(
 			$lbFactory::SHUTDOWN_NORMAL,
-			$postCommitWork,
+			null,
 			$cpIndex,
 			$cpClientId
 		);
@@ -912,24 +911,15 @@ class MediaWiki {
 			// should commit, print the output, do deferred updates, jobs, and profiling.
 		}
 
-		// GUI-ify and stash the page output in MediaWiki::doPreOutputCommit()
-		$buffer = null;
-		$outputWork = static function () use ( $output, &$buffer ) {
-			if ( $buffer === null ) {
-				$buffer = $output->output( true );
-			}
-
-			return $buffer;
-		};
-
 		// Commit any changes in the current transaction round so that:
 		// a) the transaction is not rolled back after success output was already sent
 		// b) error output is not jumbled together with success output in the response
-		$this->doPreOutputCommit( $outputWork );
+		$this->doPreOutputCommit();
 		// If needed, push a deferred update to run jobs after the output is send
 		$this->schedulePostSendJobs();
+		// Ask OutputPage/Skin to render the page output
 		// If no exceptions occurred then send the output since it is safe now
-		$this->outputResponsePayload( $outputWork() );
+		$this->outputResponsePayload( $output->output( true ) );
 	}
 
 	/**
diff --git a/includes/libs/rdbms/lbfactory/LBFactory.php b/includes/libs/rdbms/lbfactory/LBFactory.php
index c39c0c1badd..7d812e07437 100644
--- a/includes/libs/rdbms/lbfactory/LBFactory.php
+++ b/includes/libs/rdbms/lbfactory/LBFactory.php
@@ -318,7 +318,7 @@ abstract class LBFactory implements ILBFactory {
 
 		$chronProt = $this->getChronologyProtector();
 		if ( ( $flags & self::SHUTDOWN_NO_CHRONPROT ) != self::SHUTDOWN_NO_CHRONPROT ) {
-			$this->shutdownChronologyProtector( $chronProt, $workCallback, $cpIndex );
+			$this->shutdownChronologyProtector( $chronProt, $cpIndex );
 			$this->replLogger->debug( __METHOD__ . ': finished ChronologyProtector shutdown' );
 		}
 		$cpClientId = $chronProt->getClientId();
@@ -705,32 +705,17 @@ abstract class LBFactory implements ILBFactory {
 	 * Get and record all of the staged DB positions into persistent memory storage
 	 *
 	 * @param ChronologyProtector $cp
-	 * @param callable|null $workCallback Work to do instead of waiting on syncing positions
 	 * @param int|null &$cpIndex DB position key write counter; incremented on update [returned]
 	 */
 	protected function shutdownChronologyProtector(
-		ChronologyProtector $cp, $workCallback, &$cpIndex = null
+		ChronologyProtector $cp, &$cpIndex = null
 	) {
 		// Remark all of the relevant DB primary positions
 		foreach ( $this->getLBsForOwner() as $lb ) {
 			$cp->stageSessionReplicationPosition( $lb );
 		}
 		// Write the positions to the persistent stash
-		$unsavedPositions = $cp->persistSessionReplicationPositions( $cpIndex );
-		if ( $unsavedPositions && $workCallback ) {
-			// Invoke callback in case it did not cache the result yet
-			$workCallback();
-		}
-		// If the positions failed to write to the stash, then wait on the local datacenter
-		// replica DBs to catch up before sending an HTTP response. As long as the request that
-		// caused such DB writes occurred in the primary datacenter, and clients are temporarily
-		// pinned to the primary datacenter after causing DB writes, then this should suffice.
-		foreach ( $this->getLBsForOwner() as $lb ) {
-			$primaryName = $lb->getServerName( $lb->getWriterIndex() );
-			if ( isset( $unsavedPositions[$primaryName] ) ) {
-				$lb->waitForAll( $unsavedPositions[$primaryName] );
-			}
-		}
+		$cp->persistSessionReplicationPositions( $cpIndex );
 	}
 
 	/**