In earlier versions of the sync rep patch, waiters removed themselves from
the queue, but now walsender removes them before doing the wakeup.
Report by Fujii Masao.
/*
* Current location of the head of the queue. All waiters should have
- * a waitLSN that follows this value, or they are currently being woken
- * to remove themselves from the queue. Protected by SyncRepLock.
+ * a waitLSN that follows this value. Protected by SyncRepLock.
*/
XLogRecPtr lsn;