diff --git a/sys/amd64/amd64/db_interface.c b/sys/amd64/amd64/db_interface.c
index 2ba81daeefee..26635d3eddf5 100644
--- a/sys/amd64/amd64/db_interface.c
+++ b/sys/amd64/amd64/db_interface.c
@@ -58,7 +58,6 @@ int	db_active;
 db_regs_t ddb_regs;
 
 static jmp_buf	db_global_jmpbuf;
-static int	db_global_jmpbuf_valid;
 
 #ifdef __GNUC__
 #define	rss() ({u_short ss; __asm __volatile("mov %%ss,%0" : "=r" (ss)); ss;})
@@ -119,7 +118,7 @@ kdb_trap(type, code, regs)
 	 * non-ddb functions.  db_nofault only applies to memory accesses by
 	 * internal ddb commands.
 	 */
-	if (db_global_jmpbuf_valid)
+	if (db_active)
 	    longjmp(db_global_jmpbuf, 1);
 
 	/*
@@ -154,16 +153,17 @@ kdb_trap(type, code, regs)
 #endif /* SMP */
 
 	(void) setjmp(db_global_jmpbuf);
-	db_global_jmpbuf_valid = TRUE;
-	db_active++;
 	if (ddb_mode) {
-	    cndbctl(TRUE);
+	    if (!db_active)
+		cndbctl(TRUE);
+	    db_active = 1;
 	    db_trap(type, code);
 	    cndbctl(FALSE);
-	} else
+	} else {
+	    db_active = 1;
 	    gdb_handle_exception(&ddb_regs, type, code);
-	db_active--;
-	db_global_jmpbuf_valid = FALSE;
+	}
+	db_active = 0;
 
 #ifdef SMP
 #ifdef CPUSTOP_ON_DDBBREAK
diff --git a/sys/ddb/db_ps.c b/sys/ddb/db_ps.c
index 05c0778159d9..7025ee3fda6a 100644
--- a/sys/ddb/db_ps.c
+++ b/sys/ddb/db_ps.c
@@ -120,14 +120,15 @@ db_ps(dummy1, dummy2, dummy3, dummy4)
 		}
 		db_printf("%5d %8p %8p %4d %5d %5d %07x %-4s",
 		    p->p_pid, (volatile void *)p, (void *)p->p_uarea, 
-		    p->p_ucred ? p->p_ucred->cr_ruid : 0, pp->p_pid,
-		    p->p_pgrp ? p->p_pgrp->pg_id : 0, p->p_flag, state);
+		    p->p_ucred != NULL ? p->p_ucred->cr_ruid : 0, pp->p_pid,
+		    p->p_pgrp != NULL ? p->p_pgrp->pg_id : 0, p->p_flag,
+		    state);
 		if (p->p_flag & P_KSES) {
 			db_printf("(threaded)  %s\n", p->p_comm);
 			FOREACH_THREAD_IN_PROC(p, td) {
 				db_printf( ".  .  .  .  .  .  .  "
 				           ".  thread %p   .  .  .  ", td);
-				if (td->td_wchan) {
+				if (td->td_wchan != NULL) {
 					db_printf("SLP %6s %8p\n", td->td_wmesg,
 					    (void *)td->td_wchan);
 				} else if (td->td_state == TDS_MTX) {
@@ -139,10 +140,10 @@ db_ps(dummy1, dummy2, dummy3, dummy4)
 			}
 		} else {
 			td = FIRST_THREAD_IN_PROC(p);
-			if (td->td_wchan) {
+			if (td != NULL && td->td_wchan != NULL) {
 				db_printf("  %-6s %8p", td->td_wmesg,
 				    (void *)td->td_wchan);
-			} else if (td->td_state == TDS_MTX) {
+			} else if (td != NULL && td->td_state == TDS_MTX) {
 				db_printf("  %6s %8p", td->td_mtxname,
 				    (void *)td->td_blocked);
 			} else {
diff --git a/sys/i386/i386/db_interface.c b/sys/i386/i386/db_interface.c
index 2ba81daeefee..26635d3eddf5 100644
--- a/sys/i386/i386/db_interface.c
+++ b/sys/i386/i386/db_interface.c
@@ -58,7 +58,6 @@ int	db_active;
 db_regs_t ddb_regs;
 
 static jmp_buf	db_global_jmpbuf;
-static int	db_global_jmpbuf_valid;
 
 #ifdef __GNUC__
 #define	rss() ({u_short ss; __asm __volatile("mov %%ss,%0" : "=r" (ss)); ss;})
@@ -119,7 +118,7 @@ kdb_trap(type, code, regs)
 	 * non-ddb functions.  db_nofault only applies to memory accesses by
 	 * internal ddb commands.
 	 */
-	if (db_global_jmpbuf_valid)
+	if (db_active)
 	    longjmp(db_global_jmpbuf, 1);
 
 	/*
@@ -154,16 +153,17 @@ kdb_trap(type, code, regs)
 #endif /* SMP */
 
 	(void) setjmp(db_global_jmpbuf);
-	db_global_jmpbuf_valid = TRUE;
-	db_active++;
 	if (ddb_mode) {
-	    cndbctl(TRUE);
+	    if (!db_active)
+		cndbctl(TRUE);
+	    db_active = 1;
 	    db_trap(type, code);
 	    cndbctl(FALSE);
-	} else
+	} else {
+	    db_active = 1;
 	    gdb_handle_exception(&ddb_regs, type, code);
-	db_active--;
-	db_global_jmpbuf_valid = FALSE;
+	}
+	db_active = 0;
 
 #ifdef SMP
 #ifdef CPUSTOP_ON_DDBBREAK