Remove MUTEX_DECLARE() and MTX_COLD. Instead, postpone full mutex

initialization until after malloc() is safe to call, then iterate through
all mutexes and complete their initialization.

This change is necessary in order to avoid some circular bootstrapping
dependencies.

22 files changed, 300 insertions, 150 deletions

diff --git a/sys/alpha/alpha/machdep.c b/sys/alpha/alpha/machdep.c
index d220797..ecbc9fa 100644
--- a/sys/alpha/alpha/machdep.c
+++ b/sys/alpha/alpha/machdep.c
@@ -154,8 +154,8 @@ struct bootinfo_kernel bootinfo;
 
 struct cpuhead cpuhead;
 
-MUTEX_DECLARE( ,sched_lock);
-MUTEX_DECLARE( ,Giant);
+struct mtx sched_lock;
+struct mtx Giant;
 
 struct	user *proc0paddr;
 
@@ -1003,8 +1003,8 @@ alpha_init(pfn, ptb, bim, bip, biv)
 	/*
 	 * Initialise mutexes.
 	 */
-	mtx_init(&Giant, "Giant", MTX_DEF | MTX_COLD | MTX_RECURSE);
-	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&Giant, "Giant", MTX_DEF | MTX_RECURSE);
+	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_RECURSE);
 
 	/*
 	 * Look at arguments passed to us and compute boothowto.
diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 01cee5e..1bdcb0e 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -249,8 +249,8 @@ static struct globaldata __globaldata;
 
 struct cpuhead cpuhead;
 
-MUTEX_DECLARE(,sched_lock);
-MUTEX_DECLARE(,Giant);
+struct mtx sched_lock;
+struct mtx Giant;
 
 static void
 cpu_startup(dummy)
@@ -441,7 +441,7 @@ again:
 	SLIST_INIT(&cpuhead);
 	SLIST_INSERT_HEAD(&cpuhead, GLOBALDATA, gd_allcpu);
 
-	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_RECURSE);
 
 #ifdef SMP
 	/*
@@ -1939,7 +1939,7 @@ init386(first)
 	/*
 	 * We need this mutex before the console probe.
 	 */
-	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_RECURSE);
 
 	/*
 	 * Initialize the console before we print anything out.
@@ -1954,7 +1954,7 @@ init386(first)
 	/*
 	 * Giant is used early for at least debugger traps and unexpected traps.
 	 */
-	mtx_init(&Giant, "Giant", MTX_DEF | MTX_COLD | MTX_RECURSE);
+	mtx_init(&Giant, "Giant", MTX_DEF | MTX_RECURSE);
 
 #ifdef DDB
 	kdb_init();
diff --git a/sys/amd64/amd64/tsc.c b/sys/amd64/amd64/tsc.c
index b34567b..14bcd93 100644
--- a/sys/amd64/amd64/tsc.c
+++ b/sys/amd64/amd64/tsc.c
@@ -140,7 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/amd64/isa/clock.c b/sys/amd64/isa/clock.c
index b34567b..14bcd93 100644
--- a/sys/amd64/isa/clock.c
+++ b/sys/amd64/isa/clock.c
@@ -140,7 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/i386/i386/machdep.c b/sys/i386/i386/machdep.c
index 01cee5e..1bdcb0e 100644
--- a/sys/i386/i386/machdep.c
+++ b/sys/i386/i386/machdep.c
@@ -249,8 +249,8 @@ static struct globaldata __globaldata;
 
 struct cpuhead cpuhead;
 
-MUTEX_DECLARE(,sched_lock);
-MUTEX_DECLARE(,Giant);
+struct mtx sched_lock;
+struct mtx Giant;
 
 static void
 cpu_startup(dummy)
@@ -441,7 +441,7 @@ again:
 	SLIST_INIT(&cpuhead);
 	SLIST_INSERT_HEAD(&cpuhead, GLOBALDATA, gd_allcpu);
 
-	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_RECURSE);
 
 #ifdef SMP
 	/*
@@ -1939,7 +1939,7 @@ init386(first)
 	/*
 	 * We need this mutex before the console probe.
 	 */
-	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_RECURSE);
 
 	/*
 	 * Initialize the console before we print anything out.
@@ -1954,7 +1954,7 @@ init386(first)
 	/*
 	 * Giant is used early for at least debugger traps and unexpected traps.
 	 */
-	mtx_init(&Giant, "Giant", MTX_DEF | MTX_COLD | MTX_RECURSE);
+	mtx_init(&Giant, "Giant", MTX_DEF | MTX_RECURSE);
 
 #ifdef DDB
 	kdb_init();
diff --git a/sys/i386/i386/tsc.c b/sys/i386/i386/tsc.c
index b34567b..14bcd93 100644
--- a/sys/i386/i386/tsc.c
+++ b/sys/i386/i386/tsc.c
@@ -140,7 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/i386/i386/vm86.c b/sys/i386/i386/vm86.c
index b081eef..6e2f080 100644
--- a/sys/i386/i386/vm86.c
+++ b/sys/i386/i386/vm86.c
@@ -50,7 +50,7 @@ extern int i386_extend_pcb	__P((struct proc *));
 extern int vm86pa;
 extern struct pcb *vm86pcb;
 
-MUTEX_DECLARE(static, vm86pcb_lock);
+static struct mtx vm86pcb_lock;
 
 extern int vm86_bioscall(struct vm86frame *);
 extern void vm86_biosret(struct vm86frame *);
@@ -426,7 +426,7 @@ vm86_initialize(void)
 	pcb = &vml->vml_pcb;
 	ext = &vml->vml_ext;
 
-	mtx_init(&vm86pcb_lock, "vm86pcb lock", MTX_DEF | MTX_COLD);
+	mtx_init(&vm86pcb_lock, "vm86pcb lock", MTX_DEF);
 
 	bzero(pcb, sizeof(struct pcb));
 	pcb->new_ptd = vm86pa | PG_V | PG_RW | PG_U;
diff --git a/sys/i386/isa/clock.c b/sys/i386/isa/clock.c
index b34567b..14bcd93 100644
--- a/sys/i386/isa/clock.c
+++ b/sys/i386/isa/clock.c
@@ -140,7 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/ia64/ia64/machdep.c b/sys/ia64/ia64/machdep.c
index 30f5ef6..85bcd0b 100644
--- a/sys/ia64/ia64/machdep.c
+++ b/sys/ia64/ia64/machdep.c
@@ -84,8 +84,8 @@ struct bootinfo_kernel bootinfo;
 
 struct cpuhead cpuhead;
 
-MUTEX_DECLARE( ,sched_lock);
-MUTEX_DECLARE( ,Giant);
+struct mtx sched_lock;
+struct mtx Giant;
 
 struct	user *proc0paddr;
 
@@ -590,8 +590,8 @@ ia64_init()
 	/*
 	 * Initialise mutexes.
 	 */
-	mtx_init(&Giant, "Giant", MTX_DEF | MTX_COLD | MTX_RECURSE);
-	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&Giant, "Giant", MTX_DEF | MTX_RECURSE);
+	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_RECURSE);
 
 #if 0
 	/*
diff --git a/sys/isa/atrtc.c b/sys/isa/atrtc.c
index b34567b..14bcd93 100644
--- a/sys/isa/atrtc.c
+++ b/sys/isa/atrtc.c
@@ -140,7 +140,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
index 158377d..8314a0e 100644
--- a/sys/kern/kern_lock.c
+++ b/sys/kern/kern_lock.c
@@ -80,7 +80,7 @@
 extern int lock_nmtx;
 int lock_mtx_selector;
 struct mtx *lock_mtx_array;
-MUTEX_DECLARE(static, lock_mtx);
+static struct mtx lock_mtx;
 
 static int acquire(struct lock *lkp, int extflags, int wanted);
 static int apause(struct lock *lkp, int flags);
@@ -98,7 +98,7 @@ lockmgr_init(void *dummy __unused)
 	 * initialized in a call to lockinit().
 	 */
 	if (lock_mtx_selector == 0)
-		mtx_init(&lock_mtx, "lockmgr", MTX_DEF | MTX_COLD);
+		mtx_init(&lock_mtx, "lockmgr", MTX_DEF);
 	else {
 		/*
 		 * This is necessary if (lock_nmtx == 1) and doesn't hurt
@@ -546,7 +546,7 @@ lockinit(lkp, prio, wmesg, timo, flags)
 			 * so there's no reason to protect modification of
 			 * lock_mtx_selector or lock_mtx.
 			 */
-			mtx_init(&lock_mtx, "lockmgr", MTX_DEF | MTX_COLD);
+			mtx_init(&lock_mtx, "lockmgr", MTX_DEF);
 			lock_mtx_selector = 1;
 		}
 		lkp->lk_interlock = &lock_mtx;
diff --git a/sys/kern/kern_malloc.c b/sys/kern/kern_malloc.c
index d6275b8..396f02b 100644
--- a/sys/kern/kern_malloc.c
+++ b/sys/kern/kern_malloc.c
@@ -74,7 +74,7 @@ static struct kmemusage *kmemusage;
 static char *kmembase;
 static char *kmemlimit;
 
-MUTEX_DECLARE(static, malloc_mtx);
+static struct mtx malloc_mtx;
 
 u_int vm_kmem_size;
 
@@ -439,7 +439,7 @@ kmeminit(dummy)
 #error "kmeminit: MAXALLOCSAVE too small"
 #endif
 
-	mtx_init(&malloc_mtx, "malloc", MTX_DEF | MTX_COLD);
+	mtx_init(&malloc_mtx, "malloc", MTX_DEF);
 
 	/*
 	 * Try to auto-tune the kernel memory size, so that it is
diff --git a/sys/kern/kern_mutex.c b/sys/kern/kern_mutex.c
index 0d42519..d996459 100644
--- a/sys/kern/kern_mutex.c
+++ b/sys/kern/kern_mutex.c
@@ -88,11 +88,16 @@
 #ifdef WITNESS
 static struct mtx_debug all_mtx_debug = { NULL, {NULL, NULL}, NULL, 0,
 	"All mutexes queue head" };
-static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, &all_mtx_debug,
+static struct mtx all_mtx = { 0, MTX_UNOWNED, 0, 0, {&all_mtx_debug},
 	TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
 	{ NULL, NULL }, &all_mtx, &all_mtx };
+/*
+ * Set to 0 once mutexes have been fully initialized so that witness code can be
+ * safely executed.
+ */
+static int witness_cold = 1;
 #else	/* WITNESS */
-static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, "All mutexes queue head",
+static struct mtx all_mtx = { 0, MTX_UNOWNED, 0, 0, {"All mutexes queue head"},
 	TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
 	{ NULL, NULL }, &all_mtx, &all_mtx };
 #endif	/* WITNESS */
@@ -521,6 +526,10 @@ mtx_validate(struct mtx *m, int when)
 	int i;
 	int retval = 0;
 
+#ifdef WITNESS
+	if (witness_cold)
+		return 0;
+#endif
 	if (m == &all_mtx || cold)
 		return 0;
 
@@ -576,39 +585,35 @@ mtx_validate(struct mtx *m, int when)
 void
 mtx_init(struct mtx *m, const char *t, int flag)
 {
-#ifdef WITNESS
-	struct mtx_debug *debug;
-#endif
-
 	if ((flag & MTX_QUIET) == 0)
 		CTR2(KTR_LOCK, "mtx_init 0x%p (%s)", m, t);
 #ifdef MUTEX_DEBUG
 	if (mtx_validate(m, MV_INIT))	/* diagnostic and error correction */
 		return;
 #endif
-#ifdef WITNESS
-	if (flag & MTX_COLD)
-		debug = m->mtx_debug;
-	else
-		debug = NULL;
-	if (debug == NULL) {
-#ifdef DIAGNOSTIC
-		if(cold && bootverbose)
-			printf("malloc'ing mtx_debug while cold for %s\n", t);
-#endif
 
-		/* XXX - should not use DEVBUF */
-		debug = malloc(sizeof(struct mtx_debug), M_DEVBUF,
-		    M_NOWAIT | M_ZERO);
-		MPASS(debug != NULL);
-	}
-#endif
 	bzero((void *)m, sizeof *m);
 	TAILQ_INIT(&m->mtx_blocked);
 #ifdef WITNESS
-	m->mtx_debug = debug;
-#endif
+	if (!witness_cold) {
+		/* XXX - should not use DEVBUF */
+		m->mtx_union.mtxu_debug = malloc(sizeof(struct mtx_debug),
+		    M_DEVBUF, M_NOWAIT | M_ZERO);
+		MPASS(m->mtx_union.mtxu_debug != NULL);
+
+		m->mtx_description = t;
+	} else {
+		/*
+		 * Save a pointer to the description so that witness_fixup()
+		 * can properly initialize this mutex later on.
+		 */
+		m->mtx_union.mtxu_description = t;
+	}
+#else
 	m->mtx_description = t;
+#endif
+
+	m->mtx_flags = flag;
 	m->mtx_lock = MTX_UNOWNED;
 	/* Put on all mutex queue */
 	mtx_enter(&all_mtx, MTX_DEF);
@@ -619,13 +624,20 @@ mtx_init(struct mtx *m, const char *t, int flag)
 	if (++mtx_cur_cnt > mtx_max_cnt)
 		mtx_max_cnt = mtx_cur_cnt;
 	mtx_exit(&all_mtx, MTX_DEF);
-	witness_init(m, flag);
+#ifdef WITNESS
+	if (!witness_cold)
+		witness_init(m, flag);
+#endif
 }
 
 void
 mtx_destroy(struct mtx *m)
 {
 
+#ifdef WITNESS
+	KASSERT(!witness_cold, ("%s: Cannot destroy while still cold\n",
+	    __FUNCTION__));
+#endif
 	CTR2(KTR_LOCK, "mtx_destroy 0x%p (%s)", m, m->mtx_description);
 #ifdef MUTEX_DEBUG
 	if (m->mtx_next == NULL)
@@ -653,13 +665,40 @@ mtx_destroy(struct mtx *m)
 	m->mtx_next = m->mtx_prev = NULL;
 #endif
 #ifdef WITNESS
-	free(m->mtx_debug, M_DEVBUF);
-	m->mtx_debug = NULL;
+	free(m->mtx_union.mtxu_debug, M_DEVBUF);
+	m->mtx_union.mtxu_debug = NULL;
 #endif
 	mtx_cur_cnt--;
 	mtx_exit(&all_mtx, MTX_DEF);
 }
 
+static void
+witness_fixup(void *dummy __unused)
+{
+#ifdef WITNESS
+	struct mtx *mp;
+	const char *description;
+
+	/* Iterate through all mutexes and finish up mutex initialization. */
+	for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) {
+		description = mp->mtx_union.mtxu_description;
+
+		/* XXX - should not use DEVBUF */
+		mp->mtx_union.mtxu_debug = malloc(sizeof(struct mtx_debug),
+		    M_DEVBUF, M_NOWAIT | M_ZERO);
+		MPASS(mp->mtx_union.mtxu_debug != NULL);
+
+		mp->mtx_description = description;
+
+		witness_init(mp, mp->mtx_flags);
+	}
+
+	/* Mark the witness code as being ready for use. */
+	atomic_store_rel_int(&witness_cold, 0);
+#endif
+}
+SYSINIT(wtnsfxup, SI_SUB_MUTEX, SI_ORDER_FIRST, witness_fixup, NULL)
+
 /*
  * The non-inlined versions of the mtx_*() functions are always built (above),
  * but the witness code depends on the WITNESS kernel option being specified.
@@ -716,7 +755,7 @@ int	witness_skipspin = 0;
 SYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RD, &witness_skipspin, 0,
     "");
 
-MUTEX_DECLARE(static,w_mtx);
+static struct mtx	w_mtx;
 static struct witness	*w_free;
 static struct witness	*w_all;
 static int		 w_inited;
@@ -813,6 +852,8 @@ witness_enter(struct mtx *m, int flags, const char *file, int line)
 	int go_into_ddb = 0;
 #endif /* DDB */
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	w = m->mtx_witness;
@@ -957,6 +998,8 @@ witness_exit(struct mtx *m, int flags, const char *file, int line)
 {
 	struct witness *w;
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	w = m->mtx_witness;
@@ -1003,6 +1046,8 @@ witness_try_enter(struct mtx *m, int flags, const char *file, int line)
 	struct proc *p;
 	struct witness *w = m->mtx_witness;
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	if (flags & MTX_SPIN) {
@@ -1053,6 +1098,7 @@ witness_display(void(*prnt)(const char *fmt, ...))
 {
 	struct witness *w, *w1;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	witness_levelall();
 
 	for (w = w_all; w; w = w->w_next) {
@@ -1085,6 +1131,7 @@ witness_sleep(int check_only, struct mtx *mtx, const char *file, int line)
 	char **sleep;
 	int n = 0;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	p = CURPROC;
 	for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
 	    m = LIST_NEXT(m, mtx_held)) {
@@ -1122,7 +1169,7 @@ enroll(const char *description, int flag)
 			return (NULL);
 
 	if (w_inited == 0) {
-		mtx_init(&w_mtx, "witness lock", MTX_COLD | MTX_SPIN);
+		mtx_init(&w_mtx, "witness lock", MTX_SPIN);
 		for (i = 0; i < WITNESS_COUNT; i++) {
 			w = &w_data[i];
 			witness_free(w);
@@ -1401,6 +1448,7 @@ witness_list(struct proc *p)
 	struct mtx *m;
 	int nheld;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	nheld = 0;
 	for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
 	    m = LIST_NEXT(m, mtx_held)) {
@@ -1416,6 +1464,8 @@ witness_list(struct proc *p)
 void
 witness_save(struct mtx *m, const char **filep, int *linep)
 {
+
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	*filep = m->mtx_witness->w_file;
 	*linep = m->mtx_witness->w_line;
 }
@@ -1423,6 +1473,8 @@ witness_save(struct mtx *m, const char **filep, int *linep)
 void
 witness_restore(struct mtx *m, const char *file, int line)
 {
+
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	m->mtx_witness->w_file = file;
 	m->mtx_witness->w_line = line;
 }
diff --git a/sys/kern/subr_turnstile.c b/sys/kern/subr_turnstile.c
index 0d42519..d996459 100644
--- a/sys/kern/subr_turnstile.c
+++ b/sys/kern/subr_turnstile.c
@@ -88,11 +88,16 @@
 #ifdef WITNESS
 static struct mtx_debug all_mtx_debug = { NULL, {NULL, NULL}, NULL, 0,
 	"All mutexes queue head" };
-static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, &all_mtx_debug,
+static struct mtx all_mtx = { 0, MTX_UNOWNED, 0, 0, {&all_mtx_debug},
 	TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
 	{ NULL, NULL }, &all_mtx, &all_mtx };
+/*
+ * Set to 0 once mutexes have been fully initialized so that witness code can be
+ * safely executed.
+ */
+static int witness_cold = 1;
 #else	/* WITNESS */
-static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, "All mutexes queue head",
+static struct mtx all_mtx = { 0, MTX_UNOWNED, 0, 0, {"All mutexes queue head"},
 	TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
 	{ NULL, NULL }, &all_mtx, &all_mtx };
 #endif	/* WITNESS */
@@ -521,6 +526,10 @@ mtx_validate(struct mtx *m, int when)
 	int i;
 	int retval = 0;
 
+#ifdef WITNESS
+	if (witness_cold)
+		return 0;
+#endif
 	if (m == &all_mtx || cold)
 		return 0;
 
@@ -576,39 +585,35 @@ mtx_validate(struct mtx *m, int when)
 void
 mtx_init(struct mtx *m, const char *t, int flag)
 {
-#ifdef WITNESS
-	struct mtx_debug *debug;
-#endif
-
 	if ((flag & MTX_QUIET) == 0)
 		CTR2(KTR_LOCK, "mtx_init 0x%p (%s)", m, t);
 #ifdef MUTEX_DEBUG
 	if (mtx_validate(m, MV_INIT))	/* diagnostic and error correction */
 		return;
 #endif
-#ifdef WITNESS
-	if (flag & MTX_COLD)
-		debug = m->mtx_debug;
-	else
-		debug = NULL;
-	if (debug == NULL) {
-#ifdef DIAGNOSTIC
-		if(cold && bootverbose)
-			printf("malloc'ing mtx_debug while cold for %s\n", t);
-#endif
 
-		/* XXX - should not use DEVBUF */
-		debug = malloc(sizeof(struct mtx_debug), M_DEVBUF,
-		    M_NOWAIT | M_ZERO);
-		MPASS(debug != NULL);
-	}
-#endif
 	bzero((void *)m, sizeof *m);
 	TAILQ_INIT(&m->mtx_blocked);
 #ifdef WITNESS
-	m->mtx_debug = debug;
-#endif
+	if (!witness_cold) {
+		/* XXX - should not use DEVBUF */
+		m->mtx_union.mtxu_debug = malloc(sizeof(struct mtx_debug),
+		    M_DEVBUF, M_NOWAIT | M_ZERO);
+		MPASS(m->mtx_union.mtxu_debug != NULL);
+
+		m->mtx_description = t;
+	} else {
+		/*
+		 * Save a pointer to the description so that witness_fixup()
+		 * can properly initialize this mutex later on.
+		 */
+		m->mtx_union.mtxu_description = t;
+	}
+#else
 	m->mtx_description = t;
+#endif
+
+	m->mtx_flags = flag;
 	m->mtx_lock = MTX_UNOWNED;
 	/* Put on all mutex queue */
 	mtx_enter(&all_mtx, MTX_DEF);
@@ -619,13 +624,20 @@ mtx_init(struct mtx *m, const char *t, int flag)
 	if (++mtx_cur_cnt > mtx_max_cnt)
 		mtx_max_cnt = mtx_cur_cnt;
 	mtx_exit(&all_mtx, MTX_DEF);
-	witness_init(m, flag);
+#ifdef WITNESS
+	if (!witness_cold)
+		witness_init(m, flag);
+#endif
 }
 
 void
 mtx_destroy(struct mtx *m)
 {
 
+#ifdef WITNESS
+	KASSERT(!witness_cold, ("%s: Cannot destroy while still cold\n",
+	    __FUNCTION__));
+#endif
 	CTR2(KTR_LOCK, "mtx_destroy 0x%p (%s)", m, m->mtx_description);
 #ifdef MUTEX_DEBUG
 	if (m->mtx_next == NULL)
@@ -653,13 +665,40 @@ mtx_destroy(struct mtx *m)
 	m->mtx_next = m->mtx_prev = NULL;
 #endif
 #ifdef WITNESS
-	free(m->mtx_debug, M_DEVBUF);
-	m->mtx_debug = NULL;
+	free(m->mtx_union.mtxu_debug, M_DEVBUF);
+	m->mtx_union.mtxu_debug = NULL;
 #endif
 	mtx_cur_cnt--;
 	mtx_exit(&all_mtx, MTX_DEF);
 }
 
+static void
+witness_fixup(void *dummy __unused)
+{
+#ifdef WITNESS
+	struct mtx *mp;
+	const char *description;
+
+	/* Iterate through all mutexes and finish up mutex initialization. */
+	for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) {
+		description = mp->mtx_union.mtxu_description;
+
+		/* XXX - should not use DEVBUF */
+		mp->mtx_union.mtxu_debug = malloc(sizeof(struct mtx_debug),
+		    M_DEVBUF, M_NOWAIT | M_ZERO);
+		MPASS(mp->mtx_union.mtxu_debug != NULL);
+
+		mp->mtx_description = description;
+
+		witness_init(mp, mp->mtx_flags);
+	}
+
+	/* Mark the witness code as being ready for use. */
+	atomic_store_rel_int(&witness_cold, 0);
+#endif
+}
+SYSINIT(wtnsfxup, SI_SUB_MUTEX, SI_ORDER_FIRST, witness_fixup, NULL)
+
 /*
  * The non-inlined versions of the mtx_*() functions are always built (above),
  * but the witness code depends on the WITNESS kernel option being specified.
@@ -716,7 +755,7 @@ int	witness_skipspin = 0;
 SYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RD, &witness_skipspin, 0,
     "");
 
-MUTEX_DECLARE(static,w_mtx);
+static struct mtx	w_mtx;
 static struct witness	*w_free;
 static struct witness	*w_all;
 static int		 w_inited;
@@ -813,6 +852,8 @@ witness_enter(struct mtx *m, int flags, const char *file, int line)
 	int go_into_ddb = 0;
 #endif /* DDB */
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	w = m->mtx_witness;
@@ -957,6 +998,8 @@ witness_exit(struct mtx *m, int flags, const char *file, int line)
 {
 	struct witness *w;
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	w = m->mtx_witness;
@@ -1003,6 +1046,8 @@ witness_try_enter(struct mtx *m, int flags, const char *file, int line)
 	struct proc *p;
 	struct witness *w = m->mtx_witness;
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	if (flags & MTX_SPIN) {
@@ -1053,6 +1098,7 @@ witness_display(void(*prnt)(const char *fmt, ...))
 {
 	struct witness *w, *w1;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	witness_levelall();
 
 	for (w = w_all; w; w = w->w_next) {
@@ -1085,6 +1131,7 @@ witness_sleep(int check_only, struct mtx *mtx, const char *file, int line)
 	char **sleep;
 	int n = 0;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	p = CURPROC;
 	for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
 	    m = LIST_NEXT(m, mtx_held)) {
@@ -1122,7 +1169,7 @@ enroll(const char *description, int flag)
 			return (NULL);
 
 	if (w_inited == 0) {
-		mtx_init(&w_mtx, "witness lock", MTX_COLD | MTX_SPIN);
+		mtx_init(&w_mtx, "witness lock", MTX_SPIN);
 		for (i = 0; i < WITNESS_COUNT; i++) {
 			w = &w_data[i];
 			witness_free(w);
@@ -1401,6 +1448,7 @@ witness_list(struct proc *p)
 	struct mtx *m;
 	int nheld;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	nheld = 0;
 	for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
 	    m = LIST_NEXT(m, mtx_held)) {
@@ -1416,6 +1464,8 @@ witness_list(struct proc *p)
 void
 witness_save(struct mtx *m, const char **filep, int *linep)
 {
+
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	*filep = m->mtx_witness->w_file;
 	*linep = m->mtx_witness->w_line;
 }
@@ -1423,6 +1473,8 @@ witness_save(struct mtx *m, const char **filep, int *linep)
 void
 witness_restore(struct mtx *m, const char *file, int line)
 {
+
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	m->mtx_witness->w_file = file;
 	m->mtx_witness->w_line = line;
 }
diff --git a/sys/kern/subr_witness.c b/sys/kern/subr_witness.c
index 0d42519..d996459 100644
--- a/sys/kern/subr_witness.c
+++ b/sys/kern/subr_witness.c
@@ -88,11 +88,16 @@
 #ifdef WITNESS
 static struct mtx_debug all_mtx_debug = { NULL, {NULL, NULL}, NULL, 0,
 	"All mutexes queue head" };
-static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, &all_mtx_debug,
+static struct mtx all_mtx = { 0, MTX_UNOWNED, 0, 0, {&all_mtx_debug},
 	TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
 	{ NULL, NULL }, &all_mtx, &all_mtx };
+/*
+ * Set to 0 once mutexes have been fully initialized so that witness code can be
+ * safely executed.
+ */
+static int witness_cold = 1;
 #else	/* WITNESS */
-static struct mtx all_mtx = { MTX_UNOWNED, 0, 0, "All mutexes queue head",
+static struct mtx all_mtx = { 0, MTX_UNOWNED, 0, 0, {"All mutexes queue head"},
 	TAILQ_HEAD_INITIALIZER(all_mtx.mtx_blocked),
 	{ NULL, NULL }, &all_mtx, &all_mtx };
 #endif	/* WITNESS */
@@ -521,6 +526,10 @@ mtx_validate(struct mtx *m, int when)
 	int i;
 	int retval = 0;
 
+#ifdef WITNESS
+	if (witness_cold)
+		return 0;
+#endif
 	if (m == &all_mtx || cold)
 		return 0;
 
@@ -576,39 +585,35 @@ mtx_validate(struct mtx *m, int when)
 void
 mtx_init(struct mtx *m, const char *t, int flag)
 {
-#ifdef WITNESS
-	struct mtx_debug *debug;
-#endif
-
 	if ((flag & MTX_QUIET) == 0)
 		CTR2(KTR_LOCK, "mtx_init 0x%p (%s)", m, t);
 #ifdef MUTEX_DEBUG
 	if (mtx_validate(m, MV_INIT))	/* diagnostic and error correction */
 		return;
 #endif
-#ifdef WITNESS
-	if (flag & MTX_COLD)
-		debug = m->mtx_debug;
-	else
-		debug = NULL;
-	if (debug == NULL) {
-#ifdef DIAGNOSTIC
-		if(cold && bootverbose)
-			printf("malloc'ing mtx_debug while cold for %s\n", t);
-#endif
 
-		/* XXX - should not use DEVBUF */
-		debug = malloc(sizeof(struct mtx_debug), M_DEVBUF,
-		    M_NOWAIT | M_ZERO);
-		MPASS(debug != NULL);
-	}
-#endif
 	bzero((void *)m, sizeof *m);
 	TAILQ_INIT(&m->mtx_blocked);
 #ifdef WITNESS
-	m->mtx_debug = debug;
-#endif
+	if (!witness_cold) {
+		/* XXX - should not use DEVBUF */
+		m->mtx_union.mtxu_debug = malloc(sizeof(struct mtx_debug),
+		    M_DEVBUF, M_NOWAIT | M_ZERO);
+		MPASS(m->mtx_union.mtxu_debug != NULL);
+
+		m->mtx_description = t;
+	} else {
+		/*
+		 * Save a pointer to the description so that witness_fixup()
+		 * can properly initialize this mutex later on.
+		 */
+		m->mtx_union.mtxu_description = t;
+	}
+#else
 	m->mtx_description = t;
+#endif
+
+	m->mtx_flags = flag;
 	m->mtx_lock = MTX_UNOWNED;
 	/* Put on all mutex queue */
 	mtx_enter(&all_mtx, MTX_DEF);
@@ -619,13 +624,20 @@ mtx_init(struct mtx *m, const char *t, int flag)
 	if (++mtx_cur_cnt > mtx_max_cnt)
 		mtx_max_cnt = mtx_cur_cnt;
 	mtx_exit(&all_mtx, MTX_DEF);
-	witness_init(m, flag);
+#ifdef WITNESS
+	if (!witness_cold)
+		witness_init(m, flag);
+#endif
 }
 
 void
 mtx_destroy(struct mtx *m)
 {
 
+#ifdef WITNESS
+	KASSERT(!witness_cold, ("%s: Cannot destroy while still cold\n",
+	    __FUNCTION__));
+#endif
 	CTR2(KTR_LOCK, "mtx_destroy 0x%p (%s)", m, m->mtx_description);
 #ifdef MUTEX_DEBUG
 	if (m->mtx_next == NULL)
@@ -653,13 +665,40 @@ mtx_destroy(struct mtx *m)
 	m->mtx_next = m->mtx_prev = NULL;
 #endif
 #ifdef WITNESS
-	free(m->mtx_debug, M_DEVBUF);
-	m->mtx_debug = NULL;
+	free(m->mtx_union.mtxu_debug, M_DEVBUF);
+	m->mtx_union.mtxu_debug = NULL;
 #endif
 	mtx_cur_cnt--;
 	mtx_exit(&all_mtx, MTX_DEF);
 }
 
+static void
+witness_fixup(void *dummy __unused)
+{
+#ifdef WITNESS
+	struct mtx *mp;
+	const char *description;
+
+	/* Iterate through all mutexes and finish up mutex initialization. */
+	for (mp = all_mtx.mtx_next; mp != &all_mtx; mp = mp->mtx_next) {
+		description = mp->mtx_union.mtxu_description;
+
+		/* XXX - should not use DEVBUF */
+		mp->mtx_union.mtxu_debug = malloc(sizeof(struct mtx_debug),
+		    M_DEVBUF, M_NOWAIT | M_ZERO);
+		MPASS(mp->mtx_union.mtxu_debug != NULL);
+
+		mp->mtx_description = description;
+
+		witness_init(mp, mp->mtx_flags);
+	}
+
+	/* Mark the witness code as being ready for use. */
+	atomic_store_rel_int(&witness_cold, 0);
+#endif
+}
+SYSINIT(wtnsfxup, SI_SUB_MUTEX, SI_ORDER_FIRST, witness_fixup, NULL)
+
 /*
  * The non-inlined versions of the mtx_*() functions are always built (above),
  * but the witness code depends on the WITNESS kernel option being specified.
@@ -716,7 +755,7 @@ int	witness_skipspin = 0;
 SYSCTL_INT(_debug, OID_AUTO, witness_skipspin, CTLFLAG_RD, &witness_skipspin, 0,
     "");
 
-MUTEX_DECLARE(static,w_mtx);
+static struct mtx	w_mtx;
 static struct witness	*w_free;
 static struct witness	*w_all;
 static int		 w_inited;
@@ -813,6 +852,8 @@ witness_enter(struct mtx *m, int flags, const char *file, int line)
 	int go_into_ddb = 0;
 #endif /* DDB */
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	w = m->mtx_witness;
@@ -957,6 +998,8 @@ witness_exit(struct mtx *m, int flags, const char *file, int line)
 {
 	struct witness *w;
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	w = m->mtx_witness;
@@ -1003,6 +1046,8 @@ witness_try_enter(struct mtx *m, int flags, const char *file, int line)
 	struct proc *p;
 	struct witness *w = m->mtx_witness;
 
+	if (witness_cold)
+		return;
 	if (panicstr)
 		return;
 	if (flags & MTX_SPIN) {
@@ -1053,6 +1098,7 @@ witness_display(void(*prnt)(const char *fmt, ...))
 {
 	struct witness *w, *w1;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	witness_levelall();
 
 	for (w = w_all; w; w = w->w_next) {
@@ -1085,6 +1131,7 @@ witness_sleep(int check_only, struct mtx *mtx, const char *file, int line)
 	char **sleep;
 	int n = 0;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	p = CURPROC;
 	for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
 	    m = LIST_NEXT(m, mtx_held)) {
@@ -1122,7 +1169,7 @@ enroll(const char *description, int flag)
 			return (NULL);
 
 	if (w_inited == 0) {
-		mtx_init(&w_mtx, "witness lock", MTX_COLD | MTX_SPIN);
+		mtx_init(&w_mtx, "witness lock", MTX_SPIN);
 		for (i = 0; i < WITNESS_COUNT; i++) {
 			w = &w_data[i];
 			witness_free(w);
@@ -1401,6 +1448,7 @@ witness_list(struct proc *p)
 	struct mtx *m;
 	int nheld;
 
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	nheld = 0;
 	for ((m = LIST_FIRST(&p->p_heldmtx)); m != NULL;
 	    m = LIST_NEXT(m, mtx_held)) {
@@ -1416,6 +1464,8 @@ witness_list(struct proc *p)
 void
 witness_save(struct mtx *m, const char **filep, int *linep)
 {
+
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	*filep = m->mtx_witness->w_file;
 	*linep = m->mtx_witness->w_line;
 }
@@ -1423,6 +1473,8 @@ witness_save(struct mtx *m, const char **filep, int *linep)
 void
 witness_restore(struct mtx *m, const char *file, int line)
 {
+
+	KASSERT(!witness_cold, ("%s: witness_cold\n", __FUNCTION__));
 	m->mtx_witness->w_file = file;
 	m->mtx_witness->w_line = line;
 }
diff --git a/sys/pc98/cbus/clock.c b/sys/pc98/cbus/clock.c
index 3acf9a4..7de923d 100644
--- a/sys/pc98/cbus/clock.c
+++ b/sys/pc98/cbus/clock.c
@@ -154,7 +154,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/pc98/cbus/pcrtc.c b/sys/pc98/cbus/pcrtc.c
index 3acf9a4..7de923d 100644
--- a/sys/pc98/cbus/pcrtc.c
+++ b/sys/pc98/cbus/pcrtc.c
@@ -154,7 +154,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/pc98/i386/machdep.c b/sys/pc98/i386/machdep.c
index cf9df15..4105324 100644
--- a/sys/pc98/i386/machdep.c
+++ b/sys/pc98/i386/machdep.c
@@ -262,8 +262,8 @@ static struct globaldata __globaldata;
 
 struct cpuhead cpuhead;
 
-MUTEX_DECLARE(,sched_lock);
-MUTEX_DECLARE(,Giant);
+struct mtx sched_lock;
+struct mtx Giant;
 
 static void
 cpu_startup(dummy)
@@ -454,7 +454,7 @@ again:
 	SLIST_INIT(&cpuhead);
 	SLIST_INSERT_HEAD(&cpuhead, GLOBALDATA, gd_allcpu);
 
-	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_RECURSE);
 
 #ifdef SMP
 	/*
@@ -2248,7 +2248,7 @@ init386(first)
 	/*
 	 * We need this mutex before the console probe.
 	 */
-	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_RECURSE);
 
 	/*
 	 * Initialize the console before we print anything out.
@@ -2263,7 +2263,7 @@ init386(first)
 	/*
 	 * Giant is used early for at least debugger traps and unexpected traps.
 	 */
-	mtx_init(&Giant, "Giant", MTX_DEF | MTX_COLD | MTX_RECURSE);
+	mtx_init(&Giant, "Giant", MTX_DEF | MTX_RECURSE);
 
 #ifdef DDB
 	kdb_init();
diff --git a/sys/pc98/pc98/clock.c b/sys/pc98/pc98/clock.c
index 3acf9a4..7de923d 100644
--- a/sys/pc98/pc98/clock.c
+++ b/sys/pc98/pc98/clock.c
@@ -154,7 +154,7 @@ int	timer0_max_count;
 u_int	tsc_freq;
 int	tsc_is_broken;
 int	wall_cmos_clock;	/* wall CMOS clock assumed if != 0 */
-MUTEX_DECLARE(,clock_lock);
+struct mtx clock_lock;
 
 static	int	beeping = 0;
 static	const u_char daysinmonth[] = {31,28,31,30,31,30,31,31,30,31,30,31};
diff --git a/sys/pc98/pc98/machdep.c b/sys/pc98/pc98/machdep.c
index cf9df15..4105324 100644
--- a/sys/pc98/pc98/machdep.c
+++ b/sys/pc98/pc98/machdep.c
@@ -262,8 +262,8 @@ static struct globaldata __globaldata;
 
 struct cpuhead cpuhead;
 
-MUTEX_DECLARE(,sched_lock);
-MUTEX_DECLARE(,Giant);
+struct mtx sched_lock;
+struct mtx Giant;
 
 static void
 cpu_startup(dummy)
@@ -454,7 +454,7 @@ again:
 	SLIST_INIT(&cpuhead);
 	SLIST_INSERT_HEAD(&cpuhead, GLOBALDATA, gd_allcpu);
 
-	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&sched_lock, "sched lock", MTX_SPIN | MTX_RECURSE);
 
 #ifdef SMP
 	/*
@@ -2248,7 +2248,7 @@ init386(first)
 	/*
 	 * We need this mutex before the console probe.
 	 */
-	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_COLD | MTX_RECURSE);
+	mtx_init(&clock_lock, "clk", MTX_SPIN | MTX_RECURSE);
 
 	/*
 	 * Initialize the console before we print anything out.
@@ -2263,7 +2263,7 @@ init386(first)
 	/*
 	 * Giant is used early for at least debugger traps and unexpected traps.
 	 */
-	mtx_init(&Giant, "Giant", MTX_DEF | MTX_COLD | MTX_RECURSE);
+	mtx_init(&Giant, "Giant", MTX_DEF | MTX_RECURSE);
 
 #ifdef DDB
 	kdb_init();
diff --git a/sys/sys/kernel.h b/sys/sys/kernel.h
index 48acdff..3b1be03 100644
--- a/sys/sys/kernel.h
+++ b/sys/sys/kernel.h
@@ -113,6 +113,7 @@ enum sysinit_sub_id {
 	SI_SUB_VM		= 0x1000000,	/* virtual memory system init*/
 	SI_SUB_KMEM		= 0x1800000,	/* kernel memory*/
 	SI_SUB_KVM_RSRC		= 0x1A00000,	/* kvm operational limits*/
+	SI_SUB_MUTEX		= 0x1A80000,	/* mutex (witness) fixup */
 	SI_SUB_LOCK		= 0x1B00000,	/* lockmgr locks */
 	SI_SUB_EVENTHANDLER	= 0x1C00000,	/* eventhandler init */
 	SI_SUB_CPU		= 0x2000000,	/* CPU resource(s)*/
diff --git a/sys/sys/mutex.h b/sys/sys/mutex.h
index e4660ec..4ce9d36 100644
--- a/sys/sys/mutex.h
+++ b/sys/sys/mutex.h
@@ -73,8 +73,7 @@
 #define	MTX_NOSWITCH	0x20		/* Do not switch on release */
 #define	MTX_FIRST	0x40		/* First spin lock holder */
 #define MTX_TOPHALF	0x80		/* Interrupts not disabled on spin */
-#define MTX_COLD	0x100		/* Mutex init'd before malloc works */
-#define	MTX_QUIET	0x200		/* Don't log a mutex event */
+#define	MTX_QUIET	0x100		/* Don't log a mutex event */
 
 /* options that should be passed on to mtx_enter_hard, mtx_exit_hard */
 #define	MTX_HARDOPTS	(MTX_SPIN | MTX_FIRST | MTX_TOPHALF | MTX_NOSWITCH)
@@ -98,11 +97,13 @@ struct mtx_debug {
 	const char	*mtxd_description;
 };
 
-#define mtx_description	mtx_debug->mtxd_description
-#define mtx_held	mtx_debug->mtxd_held
-#define	mtx_line	mtx_debug->mtxd_line
-#define	mtx_file	mtx_debug->mtxd_file
-#define	mtx_witness	mtx_debug->mtxd_witness
+#define mtx_description	mtx_union.mtxu_debug->mtxd_description
+#define mtx_held	mtx_union.mtxu_debug->mtxd_held
+#define	mtx_line	mtx_union.mtxu_debug->mtxd_line
+#define	mtx_file	mtx_union.mtxu_debug->mtxd_file
+#define	mtx_witness	mtx_union.mtxu_debug->mtxd_witness
+#else	/* WITNESS */
+#define mtx_description	mtx_union.mtxu_description
 #endif	/* WITNESS */
 
 /*
@@ -112,25 +113,17 @@ struct mtx {
 	volatile uintptr_t mtx_lock;	/* lock owner/gate/flags */
 	volatile u_int	mtx_recurse;	/* number of recursive holds */
 	u_int		mtx_saveintr;	/* saved flags (for spin locks) */
-#ifdef WITNESS
-	struct mtx_debug *mtx_debug;
-#else
-	const char	*mtx_description;
-#endif
+	int		mtx_flags;	/* flags passed to mtx_init() */
+	union {
+		struct mtx_debug *mtxu_debug;
+		const char	*mtxu_description;
+	}		mtx_union;
 	TAILQ_HEAD(, proc) mtx_blocked;
 	LIST_ENTRY(mtx)	mtx_contested;
 	struct mtx	*mtx_next;	/* all locks in system */
 	struct mtx	*mtx_prev;
 };
 
-#ifdef	WITNESS
-#define	MUTEX_DECLARE(modifiers, name)					\
-	static struct mtx_debug __mtx_debug_##name;			\
-	modifiers struct mtx name = { 0, 0, 0, &__mtx_debug_##name }
-#else
-#define MUTEX_DECLARE(modifiers, name)	modifiers struct mtx name
-#endif
-
 #define mp_fixme(string)
 
 #ifdef _KERNEL