Inhibit NMI watchdog when Alt-SysRq-T operation is underway

On large memory configuration with not so fast CPUs the NMI watchdog is
triggered when memory addresses are being gathered and printed.  The code
paths for Alt-SysRq-t are sprinkled with touch_nmi_watchdog in various
places but not in this routine (or in the loop that utilizes this
function).  The patch has been tested for regression on large CPU+memory
configuration (128 logical CPUs + 224 GB) and 1,2,4,16-CPU sockets with
various memory sizes (1,2,4,6,20).

Cc: Andi Kleen <ak@suse.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/x86_64/kernel/traps.c

@@ -330,6 +330,7 @@ static int print_trace_stack(void *data, char *name)
 
 static void print_trace_address(void *data, unsigned long addr)
 {
+	touch_nmi_watchdog();
 	printk_address(addr);
 }