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SubjectRe: [PATCH v3 07/22] kthread: Detect when a kthread work is used by more workers
On Tue, Nov 24, 2015 at 11:06:50AM +0100, Petr Mladek wrote:
> On Mon 2015-11-23 17:27:03, Tejun Heo wrote:
> > Hello,
> >
> > On Wed, Nov 18, 2015 at 02:25:12PM +0100, Petr Mladek wrote:
> > > @@ -610,6 +625,12 @@ repeat:
> > > if (work) {
> > > __set_current_state(TASK_RUNNING);
> > > work->func(work);
> > > +
> > > + spin_lock_irq(&worker->lock);
> > > + /* Allow to queue the work into another worker */
> > > + if (!kthread_work_pending(work))
> > > + work->worker = NULL;
> > > + spin_unlock_irq(&worker->lock);
> >
> > Doesn't this mean that the work item can't be freed from its callback?
> > That pattern tends to happen regularly.
>
> I am not sure if I understand your question. Do you mean switching
> work->func during the life time of the struct kthread_work? This
> should not be affected by the above code.

No, work->func(work) doing: kfree(work).

That is indeed something quite frequently done, and since you now have
references to work after calling func, things would go *boom* rather
quickly.


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