4 files changed, 20 insertions, 8 deletions
diff --git a/src/backend/lib/ilist.c b/src/backend/lib/ilist.c
index 957a118122..eb23fa1c68 100644
--- a/src/backend/lib/ilist.c
+++ b/src/backend/lib/ilist.c
@@ -28,7 +28,7 @@
  *
  * It is not allowed to delete a 'node' which is is not in the list 'head'
  *
- * Caution: this is O(n)
+ * Caution: this is O(n); consider using slist_delete_current() instead.
  */
 void
 slist_delete(slist_head *head, slist_node *node)
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index ada24e905e..f807c9cfa1 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -267,15 +267,20 @@ BackgroundWorkerStateChange(void)
 /*
  * Forget about a background worker that's no longer needed.
  *
- * At present, this only happens when a background worker marked
- * BGW_NEVER_RESTART exits.  This function should only be invoked in
- * the postmaster.
+ * The worker must be identified by passing an slist_mutable_iter that
+ * points to it.  This convention allows deletion of workers during
+ * searches of the worker list, and saves having to search the list again.
+ *
+ * This function must be invoked only in the postmaster.
  */
 void
-ForgetBackgroundWorker(RegisteredBgWorker *rw)
+ForgetBackgroundWorker(slist_mutable_iter *cur)
 {
+	RegisteredBgWorker *rw;
 	BackgroundWorkerSlot *slot;
 
+	rw = slist_container(RegisteredBgWorker, rw_lnode, cur->cur);
+
 	Assert(rw->rw_shmem_slot < max_worker_processes);
 	slot = &BackgroundWorkerData->slot[rw->rw_shmem_slot];
 	slot->in_use = false;
@@ -284,7 +289,7 @@ ForgetBackgroundWorker(RegisteredBgWorker *rw)
 			(errmsg("unregistering background worker: %s",
 				rw->rw_worker.bgw_name)));
 
-	slist_delete(&BackgroundWorkerList, &rw->rw_lnode);
+	slist_delete_current(cur);
 	free(rw);
 }
 
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index e539bac0c1..a52377fc9d 100644
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -3602,6 +3602,13 @@ pgstat_write_statsfiles(bool permanent, bool allDbs)
 	{
 		slist_mutable_iter iter;
 
+		/*
+		 * Strictly speaking we should do slist_delete_current() before
+		 * freeing each request struct.  We skip that and instead
+		 * re-initialize the list header at the end.  Nonetheless, we must use
+		 * slist_foreach_modify, not just slist_foreach, since we will free
+		 * the node's storage before advancing.
+		 */
 		slist_foreach_modify(iter, &last_statrequests)
 		{
 			DBWriteRequest *req;
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 7894217ed5..e6d750d4d3 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -1452,7 +1452,7 @@ DetermineSleepTime(struct timeval * timeout)
 
 			if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
 			{
-				ForgetBackgroundWorker(rw);
+				ForgetBackgroundWorker(&siter);
 				continue;
 			}
 
@@ -5641,7 +5641,7 @@ StartOneBackgroundWorker(void)
 		{
 			if (rw->rw_worker.bgw_restart_time == BGW_NEVER_RESTART)
 			{
-				ForgetBackgroundWorker(rw);
+				ForgetBackgroundWorker(&iter);
 				continue;
 			}