2006-03-08 07:28:01

by Kenji Kaneshige

Subject: [PATCH][BUG] fix bug in ACPI based CPU hotplug

Hi,

I found a bug in ACPI based CPU hotplug code. Because of this bug,
ACPI based CPU hotplug will always fail if NR_CPUS is equal to or
more than 255.

Thanks,
Kenji Kaneshige


This patch fixes a serious bug in ACPI based CPU hotplug code. Because
of this bug, ACPI based CPU hotplug will always fail if NR_CPUS is
equal to or more than 255.

Signed-off-by: Kenji Kaneshige <[email protected]>
Signed-off-by: Motoyuki Itoh <[email protected]>

---
drivers/acpi/processor_core.c | 11 +++++------
1 files changed, 5 insertions(+), 6 deletions(-)

Index: linux-2.6.16-rc5-mm2/drivers/acpi/processor_core.c
===================================================================
--- linux-2.6.16-rc5-mm2.orig/drivers/acpi/processor_core.c 2006-03-07 13:42:20.000000000 +0900
+++ linux-2.6.16-rc5-mm2/drivers/acpi/processor_core.c 2006-03-08 14:03:58.000000000 +0900
@@ -382,7 +382,7 @@

/* Use the acpiid in MADT to map cpus in case of SMP */
#ifndef CONFIG_SMP
-#define convert_acpiid_to_cpu(acpi_id) (0xff)
+#define convert_acpiid_to_cpu(acpi_id) (-1)
#else

#ifdef CONFIG_IA64
@@ -395,7 +395,7 @@
#define ARCH_BAD_APICID (0xff)
#endif

-static u8 convert_acpiid_to_cpu(u8 acpi_id)
+static int convert_acpiid_to_cpu(u8 acpi_id)
{
u16 apic_id;
int i;
@@ -421,7 +421,7 @@
acpi_status status = 0;
union acpi_object object = { 0 };
struct acpi_buffer buffer = { sizeof(union acpi_object), &object };
- u8 cpu_index;
+ int cpu_index;
static int cpu0_initialized;

ACPI_FUNCTION_TRACE("acpi_processor_get_info");
@@ -466,8 +466,7 @@
cpu_index = convert_acpiid_to_cpu(pr->acpi_id);

/* Handle UP system running SMP kernel, with no LAPIC in MADT */
- if (!cpu0_initialized && (cpu_index == 0xff) &&
- (num_online_cpus() == 1)) {
+ if (!cpu0_initialized && (cpu_index < 0) && (num_online_cpus() == 1)) {
cpu_index = 0;
}

@@ -480,7 +479,7 @@
* less than the max # of CPUs. They should be ignored _iff
* they are physically not present.
*/
- if (cpu_index >= NR_CPUS) {
+ if (cpu_index < 0) {
if (ACPI_FAILURE
(acpi_processor_hotadd_init(pr->handle, &pr->id))) {
ACPI_ERROR((AE_INFO,

2006-03-08 07:37:01

by Andrew Morton

Subject: Re: [PATCH][BUG] fix bug in ACPI based CPU hotplug

Kenji Kaneshige <[email protected]> wrote:
>
> This patch fixes a serious bug in ACPI based CPU hotplug code. Because
> of this bug, ACPI based CPU hotplug will always fail if NR_CPUS is
> equal to or more than 255.

Looks rather similar to
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.16-rc5/2.6.16-rc5-mm3/broken-out/acpi-signedness-fix-2.patch
;)

I think they're functionally equivalent - the only difference is the ==-1
versus <0 comparisons.

2006-03-08 08:12:21

by Kenji Kaneshige

Subject: Re: [PATCH][BUG] fix bug in ACPI based CPU hotplug

Andrew Morton wrote:
> Kenji Kaneshige <[email protected]> wrote:
>
>>This patch fixes a serious bug in ACPI based CPU hotplug code. Because
>> of this bug, ACPI based CPU hotplug will always fail if NR_CPUS is
>> equal to or more than 255.
>
>
> Looks rather similar to
> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.16-rc5/2.6.16-rc5-mm3/broken-out/acpi-signedness-fix-2.patch
> ;)
>
> I think they're functionally equivalent - the only difference is the ==-1
> versus <0 comparisons.
>
>

Oh, I didn't noticed it.
Sorry for the noise.

Thanks,
Kenji Kaneshige