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SubjectRe: [Patch] lkdtm: avoid calling lkdtm_do_action() with spin lock held
On Sat, 28 Jan 2012 20:52:47 +0800
Cong Wang <xiyou.wangcong@gmail.com> wrote:

> lkdtm_do_action() may call sleeping functions like kmalloc(),
> so do not call it with spin lock held.
>
> Cc: Prarit Bhargava <prarit@redhat.com>
> Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
>
> ---
> diff --git a/drivers/misc/lkdtm.c b/drivers/misc/lkdtm.c
> index 150cd70..28adefe 100644
> --- a/drivers/misc/lkdtm.c
> +++ b/drivers/misc/lkdtm.c
> @@ -354,6 +354,7 @@ static void lkdtm_do_action(enum ctype which)
> static void lkdtm_handler(void)
> {
> unsigned long flags;
> + bool do_it = false;
>
> spin_lock_irqsave(&count_lock, flags);
> count--;
> @@ -361,10 +362,13 @@ static void lkdtm_handler(void)
> cp_name_to_str(cpoint), cp_type_to_str(cptype), count);
>
> if (count == 0) {
> - lkdtm_do_action(cptype);
> + do_it = true;
> count = cpoint_count;
> }
> spin_unlock_irqrestore(&count_lock, flags);
> +
> + if (do_it)
> + lkdtm_do_action(cptype);
> }
>
> static int lkdtm_register_cpoint(enum cname which)

lkdtm_handler() can be called from module IRQ handlers, so perhaps the
same problems can still happen. The patch does improve things though ;)



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