Sat Apr 18 15:56:26 2020 UTC ()

In _if_down(), release the link state change lock before calling
workqueue_wait().  Add a comment explaining how the locking here
works.

PR kern/55018.


(thorpej)

diff -r1.473 -r1.474 src/sys/net/if.c

--- src/sys/net/if.c 2020/02/21 00:26:23	1.473
+++ src/sys/net/if.c 2020/04/18 15:56:26	1.474

 @@ -1,14 +1,14 @@
-/*	$NetBSD: if.c,v 1.473 2020/02/21 00:26:23 joerg Exp $	*/
+/*	$NetBSD: if.c,v 1.474 2020/04/18 15:56:26 thorpej Exp $	*/
 /*-
  * Copyright (c) 1999, 2000, 2001, 2008 The NetBSD Foundation, Inc.
  * All rights reserved.
+ *
  * This code is derived from software contributed to The NetBSD Foundation
  * by William Studenmund and Jason R. Thorpe.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
 @@ -80,27 +80,27 @@
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
+ *
  *	@(#)if.c	8.5 (Berkeley) 1/9/95
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if.c,v 1.473 2020/02/21 00:26:23 joerg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if.c,v 1.474 2020/04/18 15:56:26 thorpej Exp $");
 #if defined(_KERNEL_OPT)
 #include "opt_inet.h"
 #include "opt_ipsec.h"
 #include "opt_atalk.h"
 #include "opt_wlan.h"
 #include "opt_net_mpsafe.h"
 #include "opt_mrouting.h"
 #endif
 #include <sys/param.h>
 #include <sys/mbuf.h>
 #include <sys/systm.h>
 @@ -2509,31 +2509,42 @@ _if_down(struct ifnet *ifp)
 	s = pserialize_read_enter();
 	IFADDR_READER_FOREACH(ifa, ifp) {
 		ifa_acquire(ifa, &psref);
 		pserialize_read_exit(s);
 		pfctlinput(PRC_IFDOWN, ifa->ifa_addr);
 		s = pserialize_read_enter();
 		ifa_release(ifa, &psref);
+	}
 	pserialize_read_exit(s);
 	curlwp_bindx(bound);
 	/*
 	 * Modification of if_link_cansched is serialized with the
 	 * ifnet ioctl lock.
+	 *
 	 * The link state change lock is taken to synchronize with the
 	 * read in if_link_state_change_work_schedule().  Once we set
 	 * this to false, our if_link_work won't be scheduled.  But
 	 * we need to wait for our if_link_work to drain in case we
 	 * lost that race.
 	 */
 	IF_LINK_STATE_CHANGE_LOCK(ifp);
 	ifp->if_link_cansched = false;
 	workqueue_wait(ifnet_link_state_wq, &ifp->if_link_work);
 	IF_LINK_STATE_CHANGE_UNLOCK(ifp);
 	workqueue_wait(ifnet_link_state_wq, &ifp->if_link_work);
 	IFQ_PURGE(&ifp->if_snd);
 #if NCARP > 0
 	if (ifp->if_carp)
 		carp_carpdev_state(ifp);
 #endif
 	rt_ifmsg(ifp);
 	DOMAIN_FOREACH(dp) {
 		if (dp->dom_if_down)
 			dp->dom_if_down(ifp);
+	}
+}
 static void