[src/trunk]: src/sys/dev/mii mii(9): Fix callout race between mii_phy_down an...

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

details:   https://anonhg.NetBSD.org/src/rev/aa214ada3f52
branches:  trunk
changeset: 1029237:aa214ada3f52
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Tue Dec 28 12:00:48 2021 +0000

description:
mii(9): Fix callout race between mii_phy_down and mii_phy_detach.

diffstat:

 sys/dev/mii/mii_physubr.c |  20 ++++++++++++++++----
 1 files changed, 16 insertions(+), 4 deletions(-)

diffs (41 lines):

diff -r 724e5f09cdcb -r aa214ada3f52 sys/dev/mii/mii_physubr.c
--- a/sys/dev/mii/mii_physubr.c Tue Dec 28 10:47:00 2021 +0000
+++ b/sys/dev/mii/mii_physubr.c Tue Dec 28 12:00:48 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: mii_physubr.c,v 1.96 2021/12/15 08:28:22 msaitoh Exp $ */
+/*     $NetBSD: mii_physubr.c,v 1.97 2021/12/28 12:00:48 riastradh Exp $       */
 
 /*-
  * Copyright (c) 1998, 1999, 2000, 2001 The NetBSD Foundation, Inc.
@@ -35,7 +35,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: mii_physubr.c,v 1.96 2021/12/15 08:28:22 msaitoh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: mii_physubr.c,v 1.97 2021/12/28 12:00:48 riastradh Exp $");
 
 #include <sys/param.h>
 #include <sys/device.h>
@@ -429,8 +429,20 @@
        KASSERT(mii_locked(sc->mii_pdata));
 
        if (sc->mii_flags & MIIF_DOINGAUTO) {
-               sc->mii_flags &= ~MIIF_DOINGAUTO;
-               callout_stop(&sc->mii_nway_ch);
+               /*
+                * Try to stop it.
+                *
+                * - If we stopped it before it expired, callout_stop
+                *   returns 0, and it is our responsibility to clear
+                *   MIIF_DOINGAUTO.
+                *
+                * - Otherwise, we're too late -- the callout has
+                *   already begun, and we must leave MIIF_DOINGAUTO
+                *   set so mii_phy_detach will wait for it to
+                *   complete.
+                */
+               if (!callout_stop(&sc->mii_nway_ch))
+                       sc->mii_flags &= ~MIIF_DOINGAUTO;
        }
 }