Ok great, thanks Greg!
On Fri, Jul 3, 2020 at 1:13 PM Gregory Nutt <spudan...@gmail.com> wrote:
>
> > I have a few spots in my code where I am doing something, and I'm just
> now
> > realizing I'm not explicitly sure if it's supported or not.
> >
> > Here is my question:
> >
> > Can work_queue be called from within a worker function that uses the same
> > work_s struct?
> Yes.
> > The documentation only says that if there is existing work, it will be
> > replaced. But what happens if there is existing work, AND it's currently
> > running?
> >
> > I have a few areas where I'm doing it, and it does seem to be working,
> but
> > I'm not sure if there are any race conditions or other considerations
> that
> > I'm not aware of.
>
> That would be clearer if that read "pending" or "queued" work instead of
> "existing" work. The data in the work queue structures is decanted when
> the work starts:
>
> 128 /* Remove the ready-to-execute work from the list */
> 129
> 130 dq_rem((struct dq_entry_s *)work, &wqueue->q);
> 131
> 132 /* Extract the work description from the entry (in
> case the work
> 133 * instance by the re-used after it has been de-queued).
> 134 */
> 135
> 136 worker = work->worker;
> 137
> 138 /* Check for a race condition where the work may be
> nullified
> 139 * before it is removed from the queue.
> 140 */
> 141
> 142 if (worker != NULL)
> 143 {
> 144 /* Extract the work argument (before re-enabling
> interrupts) */
> 145
> 146 arg = work->arg;
> 147
> 148 /* Mark the work as no longer being queued */
> 149
> 150 work->worker = NULL;
> 151
> 152 /* Do the work. Re-enable interrupts while the
> work is being
> 153 * performed... we don't have any idea how long
> this will take!
> 154 */
> 155
> 156 leave_critical_section(flags);
> 157 worker(arg);
> 158
> 159 /* Now, unfortunately, since we re-enabled
> interrupts we don't
> 160 * know the state of the work list and we will
> have to start
> 161 * back at the head of the list.
> 162 */
> 163
> 164 flags = enter_critical_section();
> 165 work = (FAR struct work_s *)wqueue->q.head;
> 166 }
>
> So the work is no longer queued with the worker function executes.
>
> Greg
>
>
>
