[src/trunk]: src/sys/kern Three MULTIPROCESSOR + LOCKDEBUG fixes:

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

details:   https://anonhg.NetBSD.org/src/rev/7901bac17c05
branches:  trunk
changeset: 481939:7901bac17c05
user:      sommerfeld <sommerfeld%NetBSD.org@localhost>
date:      Wed Feb 09 16:46:09 2000 +0000

description:
Three MULTIPROCESSOR + LOCKDEBUG fixes:
1) fix typo preventing compilation (missing comma).
2) in SLOCK_WHERE, display cpu number in the MP case.
3) the folowing race condition was observed in _simple_lock:
        cpu 1 releases lock,
        cpu 0 grabs lock
        cpu 1 sees it's already locked.
        cpu 1 sees that lock_holder== "cpu 1"
        cpu 1 assumes that it already holds it and barfs.
        cpu 0 sets lock_holder == "cpu 0"
Fix: set lock_holder to LK_NOCPU in _simple_unlock().

diffstat:

 sys/kern/kern_lock.c |  14 +++++++++++---
 1 files changed, 11 insertions(+), 3 deletions(-)

diffs (45 lines):

diff -r adde08afe2cc -r 7901bac17c05 sys/kern/kern_lock.c
--- a/sys/kern/kern_lock.c      Wed Feb 09 16:24:03 2000 +0000
+++ b/sys/kern/kern_lock.c      Wed Feb 09 16:46:09 2000 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_lock.c,v 1.25 1999/08/27 01:14:38 thorpej Exp $   */
+/*     $NetBSD: kern_lock.c,v 1.26 2000/02/09 16:46:09 sommerfeld Exp $        */
 
 /*-
  * Copyright (c) 1999 The NetBSD Foundation, Inc.
@@ -689,10 +689,17 @@
 #define        SLOCK_DEBUGGER()        /* nothing */
 #endif /* } */
 
+#ifdef MULTIPROCESSOR
+#define SLOCK_MP()             lock_printf("on cpu %d\n", cpu_number())
+#else
+#define SLOCK_MP()             /* nothing */
+#endif
+
 #define        SLOCK_WHERE(str, alp, id, l)                                    \
 do {                                                                   \
        lock_printf(str);                                               \
-       lock_printf("currently at: %s:%d\n", (id), (l));                \
+       lock_printf("lock: %p, currently at: %s:%d\n", (alp), (id), (l));               \
+       SLOCK_MP();                                                     \
        if ((alp)->lock_file != NULL)                                   \
                lock_printf("last locked: %s:%d\n", (alp)->lock_file,   \
                    (alp)->lock_line);                                  \
@@ -792,7 +799,7 @@
        if ((rv = cpu_simple_lock_try(alp)) == 0) {
                if (alp->lock_holder == cpu_id)
                        SLOCK_WHERE("simple_lock_try: locking against myself\n",
-                           alp, id l);
+                           alp, id, l);
                goto out;
        }
 #else
@@ -858,6 +865,7 @@
        alp->unlock_line = l;
 
 #if defined(MULTIPROCESSOR) /* { */
+       alp->lock_holder = LK_NOCPU;
        /* Now that we've modified all fields, release the lock. */
        cpu_simple_unlock(alp);
 #else