[PATCH 1/2] cpukit/jffs2: Set extracted nodes off-chain

[Sebastian Huber]

On 21.09.23 16:52, Kinsey Moore wrote:
> On Thu, Sep 21, 2023 at 9:47 AM Sebastian Huber 
> <sebastian.huber at embedded-brains.de 
> <mailto:sebastian.huber at embedded-brains.de>> wrote:
> 
>     On 20.09.23 20:35, Kinsey Moore wrote:
>     [...]
>      > @@ -1306,8 +1307,22 @@ static void process_delayed_work(void)
>      >       while (!rtems_chain_is_tail(&process_work_chain, node)) {
>      >               work = (struct delayed_work*) node;
>      >               rtems_chain_node* next_node = rtems_chain_next(node);
>      > +
>      > +             /*
>      > +              * Don't leave extracted node exposed to other
>     operations
>      > +              * under RTEMS_DEBUG
>      > +              */
>      > +#ifdef RTEMS_DEBUG
>      > +             mutex_lock(&delayed_work_mutex);
>      > +#endif
>      >               rtems_chain_extract(node);
>      > +#ifdef RTEMS_DEBUG
>      > +             node->next = node;
>      > +             mutex_unlock(&delayed_work_mutex);
>      > +#endif
>      > +
>      >               work->callback(&work->work);
>      > +             rtems_chain_set_off_chain(node);
>      >               node = next_node;
>      >       }
>      >   }
> 
>     This change makes no sense to me. The code should work regardless if
>     RTEMS_DEBUG is defined or not.
> 
> 
> RTEMS_DEBUG introduces a behavioral change in rtems_chain_extract() such 
> that extracted nodes are automatically set off-chain. When RTEMS_DEBUG 
> is not set, node->next is left untouched. This has to be managed because 
> this code needs the node to remain on-chain so that it is not re-queued 
> during the operation.

Yes, but while a node is on a chain you must not call 
rtems_chain_set_off_chain(). If you want to use the off-chain state, 
then you have to use this:

rtems_chain_extract(node);
rtems_chain_set_off_chain(node);

or

rtems_chain_extract_unprotected(node);
rtems_chain_set_off_chain(node);

The automatic set off-chain in RTEMS_DEBUG is just to ensure that basic 
chain operations are used in the right state.

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