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SubjectRe: [Patch] lkdtm: avoid calling lkdtm_do_action() with spin lock held
On 01/31/2012 11:35 PM, Arnd Bergmann wrote:
> On Tuesday 31 January 2012, Cong Wang wrote:
>> @@ -323,14 +323,16 @@ static void lkdtm_do_action(enum ctype which)
>> }
>> case CT_WRITE_AFTER_FREE: {
>> size_t len = 1024;
>> - u32 *data = kmalloc(len, GFP_KERNEL);
>> + u32 *data = kmalloc(len, GFP_ATOMIC);
>>
>> kfree(data);
>> - schedule();
>> + udelay(100);
>> memset(data, 0x78, len);
>> break;
>> }
>
> I can't think of why the udelay would have any positive effect here,
> if the idea of the schedule was to let some other process allocate and
> use the memory.


Hmm, on SMP udelay on this CPU will give a chance to other CPU's to use
that memory, right?

>
> Can't you just get rid of the count_lock if you use an atomic_t for the
> count and use appropriate accesses on it?
>

Good idea, will do.



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