Commit 1396bc5e authored by Liu, Jinsong's avatar Liu, Jinsong

x86: Fix cpu offline bug: cancel SYSIO method when play dead

Play dead is a fragile and tricky point of cpu offline logic.  For how
to play cpu dead, linux kernel changed several times: Very old kernel
support 3 ways to play cpu dead: mwait, SYSIO, and halt, just like
what cpuidle did when enter C3; Later, it cancel mwait and SYSIO
support, only use halt to play dead; Latest linux 2.6.38 add mwait
support when cpu dead.

This patch cancel SYSIO method when cpu dead, keep same with latest

SYSIO is an obsoleted method to enter deep C, with some tricky
hardware behavior, and seldom supported in new platform.  Xen
experiment indicate that when cpu dead, SYSIO method would trigger
unknown issue which would bring strange error.  We now cancel SYSIO
method when cpu dead, after all, correctness is more important than
power save, and btw new platform use mwait.
Signed-off-by: default avatarLiu, Jinsong <>
parent def30207
......@@ -554,7 +554,6 @@ static void acpi_dead_idle(void)
struct acpi_processor_power *power;
struct acpi_processor_cx *cx;
int unused;
if ( (power = processor_powers[smp_processor_id()]) == NULL )
goto default_halt;
......@@ -574,10 +573,6 @@ static void acpi_dead_idle(void)
__monitor((void *)&mwait_wakeup(smp_processor_id()), 0, 0);
__mwait(cx->address, 0);
unused = inl(pmtmr_ioport);
goto default_halt;
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