Yoann Padioleau noted that mach is not set in lock, therefor tests on l->m
depend on lock vs. ilock, which is inconsistent.

Reference: /n/atom/patch/applied/taslockmach
Date: Thu Jun  5 13:35:16 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/9/port/taslock.c	Thu Jun  5 13:34:28 2014
+++ /sys/src/9/port/taslock.c	Thu Jun  5 13:34:28 2014
@@ -82,6 +82,7 @@
 		l->pc = pc;
 		l->p = up;
 		l->isilock = 0;
+		l->m = MACHP(m->machno);
 #ifdef LOCKCYCLES
 		l->lockcycles = -lcycles();
 #endif
@@ -117,6 +118,7 @@
 			l->pc = pc;
 			l->p = up;
 			l->isilock = 0;
+			l->m = MACHP(m->machno);
 #ifdef LOCKCYCLES
 			l->lockcycles = -lcycles();
 #endif
--- /sys/src/nix/port/taslock.c	Thu Jun  5 13:34:29 2014
+++ /sys/src/nix/port/taslock.c	Thu Jun  5 13:34:30 2014
@@ -49,6 +49,7 @@
 		l->pc = pc;
 		l->p = up;
 		l->isilock = 0;
+		l->m = m;
 		if(LOCKCYCLES)
 			cycles(&l->lockcycles);
 
@@ -86,6 +87,7 @@
 			l->pc = pc;
 			l->p = up;
 			l->isilock = 0;
+			l->m = m;
 			if(LOCKCYCLES)
 				cycles(&l->lockcycles);
 			if(l != &waitstatslk)
@@ -220,7 +222,7 @@
 	if(islo())
 		print("iunlock while lo: pc %#p, held by %#p\n", getcallerpc(&l), l->pc);
 	if(l->m != m){
-		print("iunlock by cpu%d, locked by cpu%d: pc %#p, held by %#p\n",
+		print("iunlock by mach%d, locked by mach%d: pc %#p, held by %#p\n",
 			m->machno, l->m->machno, getcallerpc(&l), l->pc);
 	}