lkml.org 
[lkml]   [2013]   [Feb]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: io_apic.c --> "nr_ioapics" not initialized !
On Wed, 20 Feb 2013, Armin Steinhoff wrote:
> after a walk through the module "io_apic.c" in
> "/usr/src/linux/arch/x86/kernel/apic" I got the impression that the variable
> "nr_ioapics" is used but isn't initialized !
> Could it be the source of boot problems ?

Well no, unless your compiler is silly.

arch/x86/kernel/apic/io_apic.c:int nr_ioapics;

That's initialized to 0

> Dangerous coding stile in "static struct resource * __init
> ioapic_setup_resources(int nr_ioapics)" ....

Though the brilliant brain who decided to name the argument of
ioapic_setup_resources() the same as a global variable and of course
the call site of it to do:

ioapic_res = ioapic_setup_resources(nr_ioapics);

Brilliant. Unfortunately that's completely correct C code. Though it's
confusing as hell and definitely worth to be fixed. Patch below.

Thanks,

tglx

Index: linux-2.6/arch/x86/kernel/apic/io_apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c
+++ linux-2.6/arch/x86/kernel/apic/io_apic.c
@@ -3637,25 +3637,25 @@ void __init setup_ioapic_dest(void)

static struct resource *ioapic_resources;

-static struct resource * __init ioapic_setup_resources(int nr_ioapics)
+static struct resource * __init ioapic_setup_resources(int cnt)
{
unsigned long n;
struct resource *res;
char *mem;
int i;

- if (nr_ioapics <= 0)
+ if (cnt <= 0)
return NULL;

n = IOAPIC_RESOURCE_NAME_SIZE + sizeof(struct resource);
- n *= nr_ioapics;
+ n *= cnt;

mem = alloc_bootmem(n);
res = (void *)mem;

- mem += sizeof(struct resource) * nr_ioapics;
+ mem += sizeof(struct resource) * cnt;

- for (i = 0; i < nr_ioapics; i++) {
+ for (i = 0; i < cnt; i++) {
res[i].name = mem;
res[i].flags = IORESOURCE_MEM | IORESOURCE_BUSY;
snprintf(mem, IOAPIC_RESOURCE_NAME_SIZE, "IOAPIC %u", i);

\
 
 \ /
  Last update: 2013-02-21 03:22    [W:0.116 / U:4.468 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site