[src/trunk]: src/sys/kern PR kern/54880: -current hangs in mountroot

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

details:   https://anonhg.NetBSD.org/src/rev/2cc053962e03
branches:  trunk
changeset: 1006598:2cc053962e03
user:      ad <ad%NetBSD.org@localhost>
date:      Mon Jan 20 18:48:15 2020 +0000

description:
PR kern/54880: -current hangs in mountroot

- Don't set the RW_NODEBUG flag on init, since assembly stubs can't handle it.
- rw_downgrade(): fix a case where the RW_NODEBUG flag was lost.

diffstat:

 sys/kern/kern_rwlock.c |  11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diffs (43 lines):

diff -r ef9fb5a0313d -r 2cc053962e03 sys/kern/kern_rwlock.c
--- a/sys/kern/kern_rwlock.c    Mon Jan 20 18:40:06 2020 +0000
+++ b/sys/kern/kern_rwlock.c    Mon Jan 20 18:48:15 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_rwlock.c,v 1.61 2020/01/19 18:34:24 ad Exp $      */
+/*     $NetBSD: kern_rwlock.c,v 1.62 2020/01/20 18:48:15 ad Exp $      */
 
 /*-
  * Copyright (c) 2002, 2006, 2007, 2008, 2009, 2019, 2020
@@ -39,7 +39,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.61 2020/01/19 18:34:24 ad Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rwlock.c,v 1.62 2020/01/20 18:48:15 ad Exp $");
 
 #include "opt_lockdebug.h"
 
@@ -206,10 +206,15 @@
 _rw_init(krwlock_t *rw, uintptr_t return_address)
 {
 
+#ifdef LOCKDEBUG
+       /* XXX only because the assembly stubs can't handle RW_NODEBUG */
        if (LOCKDEBUG_ALLOC(rw, &rwlock_lockops, return_address))
                rw->rw_owner = 0;
        else
                rw->rw_owner = RW_NODEBUG;
+#else
+       rw->rw_owner = 0;
+#endif
 }
 
 void
@@ -645,7 +650,7 @@
                        RW_ASSERT(rw, (rw->rw_owner & RW_HAS_WAITERS) != 0);
 
                        newown = owner & RW_NODEBUG;
-                       newown = RW_READ_INCR | RW_HAS_WAITERS |
+                       newown |= RW_READ_INCR | RW_HAS_WAITERS |
                            RW_WRITE_WANTED;
                        next = rw_cas(rw, owner, newown);
                        turnstile_exit(rw);