From 17aed2f8951d75bfb4ea8ff5fcfdb7f13dd0ce2d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Thu, 31 Mar 2022 21:55:15 +0200
Subject: [PATCH] Repair isc_task_purgeevent(), clean isc_task_unsend{,range}()

The isc_task_purgerange() was walking through all events on the task to
find a matching task.  Instead use the ISC_LINK_LINKED to find whether
the event is active.

Cleanup the related isc_task_unsend() and isc_task_unsendrange()
functions that were not used anywhere.
---
 lib/isc/include/isc/task.h | 71 --------------------------------------
 lib/isc/task.c             | 46 ++++--------------------
 2 files changed, 7 insertions(+), 110 deletions(-)

diff --git a/lib/isc/include/isc/task.h b/lib/isc/include/isc/task.h
index e5251aa4be..efc50992c9 100644
--- a/lib/isc/include/isc/task.h
+++ b/lib/isc/include/isc/task.h
@@ -54,18 +54,6 @@
  *
  * Purging calls isc_event_free() on the matching events.
  *
- * Unsending returns a list of events that matched the pattern.
- * The caller is then responsible for them.
- *
- * Consumers of events should purge, not unsend.
- *
- * Producers of events often want to remove events when the caller indicates
- * it is no longer interested in the object, e.g. by canceling a timer.
- * Sometimes this can be done by purging, but for some event types, the
- * calls to isc_event_free() cause deadlock because the event free routine
- * wants to acquire a lock the caller is already holding.  Unsending instead
- * of purging solves this problem.  As a general rule, producers should only
- * unsend events which they have sent.
  */
 
 /***
@@ -337,65 +325,6 @@ isc_task_purgeevent(isc_task_t *task, isc_event_t *event);
  *					or was marked unpurgeable.
  */
 
-unsigned int
-isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first,
-		     isc_eventtype_t last, void *tag, isc_eventlist_t *events);
-/*%<
- * Remove events from a task's event queue.
- *
- * Requires:
- *
- *\li	'task' is a valid task.
- *
- *\li	last >= first.
- *
- *\li	*events is a valid list.
- *
- * Ensures:
- *
- *\li	Events in the event queue of 'task' whose sender is 'sender', whose
- *	type is >= first and <= last, and whose tag is 'tag' will be dequeued
- *	and appended to *events.
- *
- *\li	A sender of NULL will match any sender.  A NULL tag matches any
- *	tag.
- *
- * Returns:
- *
- *\li	The number of events unsent.
- */
-
-unsigned int
-isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type, void *tag,
-		isc_eventlist_t *events);
-/*%<
- * Remove events from a task's event queue.
- *
- * Notes:
- *
- *\li	This function is equivalent to
- *
- *\code
- *		isc_task_unsendrange(task, sender, type, type, tag, events);
- *\endcode
- *
- * Requires:
- *
- *\li	'task' is a valid task.
- *
- *\li	*events is a valid list.
- *
- * Ensures:
- *
- *\li	Events in the event queue of 'task' whose sender is 'sender', whose
- *	type is 'type', and whose tag is 'tag' will be dequeued and appended
- *	to *events.
- *
- * Returns:
- *
- *\li	The number of events unsent.
- */
-
 isc_result_t
 isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action, void *arg);
 /*%<
diff --git a/lib/isc/task.c b/lib/isc/task.c
index 5d86c9d4d2..df1f4d565a 100644
--- a/lib/isc/task.c
+++ b/lib/isc/task.c
@@ -612,12 +612,10 @@ isc_task_purge(isc_task_t *task, void *sender, isc_eventtype_t type,
 
 bool
 isc_task_purgeevent(isc_task_t *task, isc_event_t *event) {
-	isc_event_t *curr_event, *next_event;
+	bool found = false;
 
 	/*
 	 * Purge 'event' from a task's event queue.
-	 *
-	 * XXXRTH:  WARNING:  This method may be removed before beta.
 	 */
 
 	REQUIRE(VALID_TASK(task));
@@ -633,52 +631,22 @@ isc_task_purgeevent(isc_task_t *task, isc_event_t *event) {
 	 */
 
 	LOCK(&task->lock);
-	for (curr_event = HEAD(task->events); curr_event != NULL;
-	     curr_event = next_event)
-	{
-		next_event = NEXT(curr_event, ev_link);
-		if (curr_event == event && PURGE_OK(event)) {
-			DEQUEUE(task->events, curr_event, ev_link);
-			task->nevents--;
-			break;
-		}
+	if (ISC_LINK_LINKED(event, ev_link)) {
+		DEQUEUE(task->events, event, ev_link);
+		task->nevents--;
+		found = true;
 	}
 	UNLOCK(&task->lock);
 
-	if (curr_event == NULL) {
+	if (!found) {
 		return (false);
 	}
 
-	isc_event_free(&curr_event);
+	isc_event_free(&event);
 
 	return (true);
 }
 
-unsigned int
-isc_task_unsendrange(isc_task_t *task, void *sender, isc_eventtype_t first,
-		     isc_eventtype_t last, void *tag, isc_eventlist_t *events) {
-	/*
-	 * Remove events from a task's event queue.
-	 */
-	REQUIRE(VALID_TASK(task));
-
-	XTRACE("isc_task_unsendrange");
-
-	return (dequeue_events(task, sender, first, last, tag, events, false));
-}
-
-unsigned int
-isc_task_unsend(isc_task_t *task, void *sender, isc_eventtype_t type, void *tag,
-		isc_eventlist_t *events) {
-	/*
-	 * Remove events from a task's event queue.
-	 */
-
-	XTRACE("isc_task_unsend");
-
-	return (dequeue_events(task, sender, type, type, tag, events, false));
-}
-
 isc_result_t
 isc_task_onshutdown(isc_task_t *task, isc_taskaction_t action, void *arg) {
 	bool disallowed = false;