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SubjectRe: route cache DoS testing and softirqs
On Tue, Mar 30, 2004 at 10:36:14AM +0530, Srivatsa Vaddagiri wrote:
> kthread_stop does:
>
> 1. kthread_stop_info.k = k;
> 2. wake_up_process(k);
>
> and if ksoftirqd were to do :
>
> a. while (!kthread_should_stop()) {
> b. __set_current_state(TASK_INTERRUPTIBLE);
> c. schedule();
> }
>
>
> There is a (narrow) possibility here that a) happens _after_ 1) as well as
> b) _after_ 2).

hmm .. I meant a) happening _before_ 1) and b) happening _after_ 2) ..

>
> a. __set_current_state(TASK_INTERRUPTIBLE);
> b. while (!kthread_should_stop()) {
> c. schedule();
> d. __set_current_state(TASK_INTERRUPTIBLE);
> }
>
> e. __set_current_state(TASK_RUNNING);
>
> In this case, even if b) happens _after_ 1) and c) _after_ 2),

Again I meant "even if b) happens _before_ 1) and c) _after_ 2) !!

> schedule simply returns immediately because task's state would have been set
> to TASK_RUNNING by 2). It goes back to the kthread_should_stop() check and
> exits!

--


Thanks and Regards,
Srivatsa Vaddagiri,
Linux Technology Center,
IBM Software Labs,
Bangalore, INDIA - 560017
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