Re: [PATCH] ACPI: do not mark TSC unstable for invalid C-states

From: Janne Kulmala
Date: Mon May 11 2009 - 16:09:42 EST


Thomas Gleixner wrote:
commit a71e4917dc0ebbcb5a0ecb7ca3486643c1c9a6e2 (ACPI: idle:
mark_tsc_unstable() at init-time, not run-time) marks TSC unstable
even on non affected systems.

The reason is that the state enumeration does not check the cx->valid
flag before calling tsc_halts_in_c(), so it marks TSC unstable for any
enumerated albeit invalid C state which is known to turn off TSC.

Check cx->valid before checking whether the TSC might become unstable.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
drivers/acpi/processor_idle.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/drivers/acpi/processor_idle.c
===================================================================
--- linux-2.6.orig/drivers/acpi/processor_idle.c
+++ linux-2.6/drivers/acpi/processor_idle.c
@@ -583,7 +583,7 @@ static int acpi_processor_power_verify(s
#if defined (CONFIG_GENERIC_TIME) && defined (CONFIG_X86)
/* TSC could halt in idle, so notify users */
- if (tsc_halts_in_c(cx->type))
+ if (cx->valid && tsc_halts_in_c(cx->type))
mark_tsc_unstable("TSC halts in idle");;

Small suggestion: can we fix the double ';' here at the same time?

#endif
switch (cx->type) {



Janne
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