[PATCH] fix cpu frequency detection in arch/i386/kernel/timers/timer_tsc.c::recalibrate_cpu_khz()

When we re-calibrate the frequency, it is likely that an interrupt (as for
example the main system clock) will be triggered by the system.  Therefore
the calibration may not be accurate.  This will also provide a fix to bug
#5266.

Many thanks to Larry Finger for helping resolving this issue.
Signed-off-by: NBruno Ducrot <ducrot@poupinou.org>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Dave Jones <davej@codemonkey.org.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/timers/timer_tsc.c

@@ -330,7 +330,9 @@ int recalibrate_cpu_khz(void)
 	unsigned int cpu_khz_old = cpu_khz;
 
 	if (cpu_has_tsc) {
+		local_irq_disable();
 		init_cpu_khz();
+		local_irq_enable();
 		cpu_data[0].loops_per_jiffy =
 		    cpufreq_scale(cpu_data[0].loops_per_jiffy,
 			          cpu_khz_old,