Commit a6a95406 authored Feb 04, 2009 by Pavel Emelyanov Committed by Ingo Molnar Feb 05, 2009

x86: fix hpet timer reinit for x86_64



There's a small problem with hpet_rtc_reinit function - it checks
for the:

	hpet_readl(HPET_COUNTER) - hpet_t1_cmp > 0

to continue increasing both the HPET_T1_CMP (register) and the
hpet_t1_cmp (variable).

But since the HPET_COUNTER is always 32-bit, if the hpet_t1_cmp
is 64-bit this condition will always be FALSE once the latter hits
the 32-bit boundary, and we can have a situation, when we don't
increase the HPET_T1_CMP register high enough.

The result - timer stops ticking, since HPET_T1_CMP becomes less,
than the COUNTER and never increased again.

The solution is (based on Linus's suggestion) to not compare 64-bits
(on 64-bit x86), but to do the comparison on 32-bit signed
integers.

Reported-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent b1792e36

arch/x86/kernel/hpet.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1075,7 +1075,7 @@ static void hpet_rtc_timer_reinit(void)
		hpet_t1_cmp += delta;
		hpet_writel(hpet_t1_cmp, HPET_T1_CMP);
		lost_ints++;
		} while ((long)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0);
		} while ((s32)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0);

		if (lost_ints) {
		if (hpet_rtc_flags & RTC_PIE)