make quick reboot work more reliably

Reference: /n/atom/patch/applied/rebootrely
Date: Thu May 29 01:25:25 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/main.c	Thu May 29 01:25:18 2014
+++ /sys/src/nix/k10/main.c	Thu May 29 01:25:19 2014
@@ -338,6 +338,7 @@
 	lapicpri(0xff);
 	m->online = 0;
 	adec(&active.nonline);
+	adec((int*)&sys->nmach);
 	ndnr();
 }
 
@@ -354,10 +355,15 @@
 	synccons();
 	procwired(up, 0);
 
-	for(i = 1; i < active.nonline; i++)
+	/*
+	 * assumptions abound that the set of processors is contiguous
+	 * cf. procflushseg
+	 */
+	for(i = active.nonline - 1; i > 0; i--){
 		kproc("apshut", apshut, (void*)i);
-	while((a=active.nonline)>1)
-		monmwait(&active.nonline, a);
+		while((a=active.nonline) == i)
+			monmwait(&active.nonline, a);
+	}
 
 	devtabshutdown();
 	pcireset();
@@ -376,7 +382,6 @@
 	f = UINT2PTR(REBOOTADDR);
 	memmove(f, rebootcode, sizeof(rebootcode));
 	print("warp32...\n");
-	coherence();		/* necessary */
 	f(PTR2UINT(entry), PADDR(code), size);
 }