2007-12-19 00:45:33

by Parag Warudkar

Subject: [PATCH] x86: Fix dmi_alloc() to not advance alloc index in case of failure

dmi_alloc() for CONFIG_X86_64 is defined to allocate from a static array
and it maintains a allocation index which is advanced each time allocation
is attempted - it gets incremented even if an allocation fails thereby
depriving any future request that may be small enough to be satisfied from
the array.

Fix this by first testing if allocation is going to be possible and
incrementing alloc index only then.

Signed-off-by: Parag Warudkar <[email protected]>

--- linux-2.6/include/asm-x86/dmi.h 2007-12-07 10:04:42.000000000 -0500
+++ linux-2.6-work/include/asm-x86/dmi.h 2007-12-18 18:08:42.000000000 -0500
@@ -22,8 +22,9 @@
static inline void *dmi_alloc(unsigned len)
{
int idx = dmi_alloc_index;
- if ((dmi_alloc_index += len) > DMI_MAX_DATA)
+ if ((dmi_alloc_index + len) > DMI_MAX_DATA)
return NULL;
+ dmi_alloc_index += len;
return dmi_alloc_data + idx;
}

2007-12-19 10:51:12

by Ingo Molnar

Subject: Re: [PATCH] x86: Fix dmi_alloc() to not advance alloc index in case of failure

* Parag Warudkar <[email protected]> wrote:

> dmi_alloc() for CONFIG_X86_64 is defined to allocate from a static
> array and it maintains a allocation index which is advanced each time
> allocation is attempted - it gets incremented even if an allocation
> fails thereby depriving any future request that may be small enough to
> be satisfied from the array.
>
> Fix this by first testing if allocation is going to be possible and
> incrementing alloc index only then.

Thanks, applied. Nice catch!

Ingo