Hello, Petr.
On Tue, Nov 24, 2015 at 11:06:50AM +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.
So, something like the following.
void my_work_fn(work)
{
struct my_struct *s = container_of(work, ...);
do something with s;
kfree(s);
}
and the queuer does
struct my_struct *s = kmalloc(sizeof(*s));
init s and s->work;
queue(&s->work);
expecting s to be freed on completion. IOW, you can't expect the work
item to remain accessible once the work function starts executing.
> The above code allows to queue an _unused_ kthread_work into any
> kthread_worker. For example, it is needed for khugepaged,
> see http://marc.info/?l=linux-kernel&m=144785344924871&w=2
> The work is static but the worker can be started/stopped
> (allocated/freed) repeatedly. It means that the work need
> to be usable with many workers. But it is associated only
> with one worker when being used.
It can just re-init work items when it restarts workers, right?
Thanks.
--
tejun
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