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

[Cong Wang]

On 02/01/2012 11:29 PM, Arnd Bergmann wrote:
> On Wednesday 01 February 2012, Cong Wang wrote:
> > 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?
>
> There is a small chance for that, but it's much less likely than it would
> be using another process on the same CPU, plus it requires SMP.

Yeah, I updated this in [PATCH 2/2] lkdtm: avoid calling sleeping 
functions in interrupt context.
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