Re: [Patch] lkdtm: avoid calling lkdtm_do_action() with spin lockheld

[Cong Wang]

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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