On Sun, 2012-07-22 at 09:49 -0700, Tejun Heo wrote:
> Hello,
>
> On Sat, Jul 21, 2012 at 02:20:06PM -0400, Andy Walls wrote:
> > > + worker->current_work = work;
> > > spin_unlock_irq(&worker->lock);
> > >
> > > if (work) {
> > > __set_current_state(TASK_RUNNING);
> > > work->func(work);
> >
> > If the call to 'work->func(work);' frees the memory pointed to by
> > 'work', 'worker->current_work' points to deallocated memory.
> > So 'worker->current_work' will only ever used as a unique 'work'
> > identifier to handle, correct?
>
> Yeah. flush_kthread_work(@work) which can only be called if @work is
> known to be alive looks at the pointer to determine whether it's the
> current work item on the worker.
OK. Thanks.
Hmmm, I didn't know about the constraint about 'known to be alive' in
the other email I just sent.
That might make calling flush_kthread_work() hard for a user to use, if
the user lets the work get freed by another thread executing the work.
> > > void flush_kthread_work(struct kthread_work *work)
> > > {
> > > - int seq = work->queue_seq;
> > > + struct kthread_flush_work fwork = {
> > > + KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
> > > + COMPLETION_INITIALIZER_ONSTACK(fwork.done),
> > > + };
> > > + struct kthread_worker *worker;
> > > + bool noop = false;
> > > +
> >
> > You might want a check for 'work == NULL' here, to gracefully handle
> > code like the following:
> workqueue's flush_work() doesn't allow %NULL pointer. I don't want to
> make the behaviors deviate and don't see much point in changing
> workqueue's behavior at this point.
OK. Fair enough.
Thanks.
Regards,
Andy
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