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

From: Cong Wang
Date: Thu Feb 02 2012 - 08:31:25 EST

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)
size_t len = 1024;
- u32 *data = kmalloc(len, GFP_KERNEL);
+ u32 *data = kmalloc(len, GFP_ATOMIC);

- schedule();
+ udelay(100);
memset(data, 0x78, len);

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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