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Commit 316da3b3 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
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x86: restrict PIT clocksource usage 



PIT clocksource is registered unconditionally even when HPET is enabled
or when PIT is replaced by the local APIC timer. In both cases PIT can
not be used as it is stopped and the readout would be stale.

Prevent registering PIT in those cases.

patch depends on:

  x86: offer is_hpet_enabled() on !CONFIG_HPET_TIMER too

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent df619e6b

arch/x86/kernel/i8253.c

+9 −1
Original line number Diff line number Diff line
@@ -197,7 +197,15 @@ static struct clocksource clocksource_pit = { 


static int __init init_pit_clocksource(void)

{

	if (num_possible_cpus() > 1) /* PIT does not scale! */

	 /*

	  * Several reasons not to register PIT as a clocksource:

	  *

	  * - On SMP PIT does not scale due to i8253_lock

	  * - when HPET is enabled

	  * - when local APIC timer is active (PIT is switched off)

	  */

	if (num_possible_cpus() > 1 || is_hpet_enabled() ||

	    pit_clockevent.mode != CLOCK_EVT_MODE_PERIODIC)

		return 0;



	clocksource_pit.mult = clocksource_hz2mult(CLOCK_TICK_RATE, 20);