[src/trunk]: src/sys/net Fix race in wg_worker kthread destruction.

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9d159c305d1d
branches:  trunk
changeset: 1013080:9d159c305d1d
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Thu Aug 20 21:34:13 2020 +0000

description:
Fix race in wg_worker kthread destruction.

Also allow the thread to migrate between CPUs -- just not while we're
in the middle of processing and holding onto things with psrefs.

diffstat:

 sys/net/if_wg.c |  22 +++++++++++-----------
 1 files changed, 11 insertions(+), 11 deletions(-)

diffs (60 lines):

diff -r 4aea1cc63d7f -r 9d159c305d1d sys/net/if_wg.c
--- a/sys/net/if_wg.c   Thu Aug 20 21:34:03 2020 +0000
+++ b/sys/net/if_wg.c   Thu Aug 20 21:34:13 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: if_wg.c,v 1.9 2020/08/20 21:34:03 riastradh Exp $      */
+/*     $NetBSD: if_wg.c,v 1.10 2020/08/20 21:34:13 riastradh Exp $     */
 
 /*
  * Copyright (C) Ryota Ozaki <ozaki.ryota%gmail.com@localhost>
@@ -43,7 +43,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: if_wg.c,v 1.9 2020/08/20 21:34:03 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: if_wg.c,v 1.10 2020/08/20 21:34:13 riastradh Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -2736,32 +2736,32 @@
 {
        struct wg_softc *wg = arg;
        struct wg_worker *wgw = wg->wg_worker;
-       int bound = curlwp_bind();
+       bool todie = false;
 
        KASSERT(wg != NULL);
        KASSERT(wgw != NULL);
 
-       while (!wgw->wgw_todie) {
+       while (!todie) {
                int reasons;
+               int bound;
 
                mutex_enter(&wgw->wgw_lock);
                /* New tasks may come during task handling */
-               if (wgw->wgw_wakeup_reasons == 0)
+               while ((reasons = wgw->wgw_wakeup_reasons) == 0 &&
+                   !(todie = wgw->wgw_todie))
                        cv_wait(&wgw->wgw_cv, &wgw->wgw_lock);
-               reasons = wgw->wgw_wakeup_reasons;
                wgw->wgw_wakeup_reasons = 0;
                mutex_exit(&wgw->wgw_lock);
 
+               bound = curlwp_bind();
                if (ISSET(reasons, WG_WAKEUP_REASON_RECEIVE_PACKETS_IPV4))
                        wg_receive_packets(wg, AF_INET);
                if (ISSET(reasons, WG_WAKEUP_REASON_RECEIVE_PACKETS_IPV6))
                        wg_receive_packets(wg, AF_INET6);
-               if (!ISSET(reasons, WG_WAKEUP_REASON_PEER))
-                       continue;
-
-               wg_process_peer_tasks(wg);
+               if (ISSET(reasons, WG_WAKEUP_REASON_PEER))
+                       wg_process_peer_tasks(wg);
+               curlwp_bindx(bound);
        }
-       curlwp_bindx(bound);
        kthread_exit(0);
 }