On Thu, Sep 21, 2023 at 10:01 AM Sebastian Huber < sebastian.hu...@embedded-brains.de> wrote:
> On 21.09.23 16:52, Kinsey Moore wrote: > > On Thu, Sep 21, 2023 at 9:47 AM Sebastian Huber > > <sebastian.hu...@embedded-brains.de > > <mailto:sebastian.hu...@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. > Yes, there is no behavior here where rtems_chain_set_off_chain() is being called on a node that is still in a chain. This section of code is entirely managing the side-effect of RTEMS_DEBUG that sets the node in the off-chain state post-extraction. In this case, that side-effect is undesirable and so a lock is in place to prevent that temporary side-effect from leaking to other parts of the system since all other off-chain checks are behind the same lock. Kinsey
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