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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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