Re: 2.6.16rc5 'found' an extra CPU.

[Andrew Morton <akpm@osdl.org>]

Ashok Raj <ashok.raj@intel.com> wrote:
>
> Local apic entries are only 8 bits, but it seemed to not be caught with 
> u8 return value result in the check
> 
> cpu_index >= NR_CPUS becomming always false.
> 
> drivers/acpi/processor_core.c: In function `acpi_processor_get_info':
> drivers/acpi/processor_core.c:483: warning: comparison is always false due to limited range of data type
> 
> 
> Signed-off-by: Ashok Raj <ashok.raj@intel.com>
> -----------------------------------------------------
>  drivers/acpi/processor_core.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> Index: linux-2.6.16-rc5-mm1/drivers/acpi/processor_core.c
> ===================================================================
> --- linux-2.6.16-rc5-mm1.orig/drivers/acpi/processor_core.c
> +++ linux-2.6.16-rc5-mm1/drivers/acpi/processor_core.c
> @@ -395,7 +395,7 @@ static int acpi_processor_remove_fs(stru
>  #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 @@ static int acpi_processor_get_info(struc
>  	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");
> @@ -466,7 +466,7 @@ static int acpi_processor_get_info(struc
>  	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) &&
> +	if (!cpu0_initialized && (cpu_index == -1) &&
>  	    (num_online_cpus() == 1)) {
>  		cpu_index = 0;
>  	}
> @@ -480,7 +480,7 @@ static int acpi_processor_get_info(struc
>  	 *  less than the max # of CPUs. They should be ignored _iff
>  	 *  they are physically not present.
>  	 */
> -	if (cpu_index >= NR_CPUS) {
> +	if (cpu_index == -1) {
>  		if (ACPI_FAILURE
>  		    (acpi_processor_hotadd_init(pr->handle, &pr->id))) {
>  			ACPI_ERROR((AE_INFO,

On a uniprocessor build this causes a crash in acpi_processor_start():

	BUG_ON((pr->id >= NR_CPUS) || (pr->id < 0));

pr->id is 255.

I could bodge around this in various ways, but the semantics of cpu IDs in
there seem to be a bit opaque, and I suspect some more thought needs to go
into it all.

As well as uniprocessor testing ;)

-
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