svn commit: r359477 - head/sys/netinet6

[Mark Johnston]

Author: markj
Date: Tue Mar 31 02:25:53 2020
New Revision: 359477
URL: https://svnweb.freebsd.org/changeset/base/359477

Log:
  Use a dedicated taskqueue thread for in6m_release_task().
  
  Interfaces may be detached from a taskqueue_thread task, for example by
  prison_complete(), so after r359438, when draining the queue we may end
  up deadlocking.
  
  Reported by:	Jenkins via lwhsu
  MFC with:	r359438

Modified:
  head/sys/netinet6/in6_mcast.c

Modified: head/sys/netinet6/in6_mcast.c
==============================================================================
--- head/sys/netinet6/in6_mcast.c	Tue Mar 31 01:18:00 2020	(r359476)
+++ head/sys/netinet6/in6_mcast.c	Tue Mar 31 02:25:53 2020	(r359477)
@@ -510,14 +510,19 @@ in6m_release(struct in6_multi *inm)
 	}
 }
 
-static struct task free_task;
+/*
+ * Interface detach can happen in a taskqueue thread context, so we must use a
+ * dedicated thread to avoid deadlocks when draining in6m_release tasks.
+ */
+TASKQUEUE_DEFINE_THREAD(in6m_free);
+static struct task in6m_free_task;
 static struct in6_multi_head in6m_free_list = SLIST_HEAD_INITIALIZER();
 static void in6m_release_task(void *arg __unused, int pending __unused);
 
 static void
 in6m_init(void)
 {
-	TASK_INIT(&free_task, 0, in6m_release_task, NULL);
+	TASK_INIT(&in6m_free_task, 0, in6m_release_task, NULL);
 }
 SYSINIT(in6m_init, SI_SUB_TASKQ, SI_ORDER_ANY, in6m_init, NULL);
 
@@ -529,13 +534,13 @@ in6m_release_list_deferred(struct in6_multi_head *inmh
 	mtx_lock(&in6_multi_free_mtx);
 	SLIST_CONCAT(&in6m_free_list, inmh, in6_multi, in6m_nrele);
 	mtx_unlock(&in6_multi_free_mtx);
-	taskqueue_enqueue(taskqueue_thread, &free_task);
+	taskqueue_enqueue(taskqueue_in6m_free, &in6m_free_task);
 }
 
 void
 in6m_release_wait(void)
 {
-	taskqueue_drain_all(taskqueue_thread);
+	taskqueue_drain_all(taskqueue_in6m_free);
 }
 
 void