[PATCH] cpukit/score: avoid NULL and races in priority mutex

[Joel Sherrill]

On Fri, Jan 3, 2020, 12:08 AM Sebastian Huber <
sebastian.huber at embedded-brains.de> wrote:

> On 03/01/2020 00:24, Gedare Bloom wrote:
> >     while ( !_Chain_Is_empty(
> &the_thread->Priority_node.Inherited_priorities ) ) {
> > +    _ISR_Disable( level );
> >       _Thread_Dequeue_priority_node(
> >         ((Thread_Priority_node*)_Chain_First(
> >           &the_thread->Priority_node.Inherited_priorities
> >         ))
> >       );
> > +    _ISR_Enable( level );
> >     }
>
> I don't know how the stuff works in detail, but this looks like a TOCTOU
> problem. Should this be changed into:
>
> _ISR_Disable( level );
> while ( !_Chain_Is_empty(
> &the_thread->Priority_node.Inherited_priorities ) ) {
>    _Thread_Dequeue_priority_node(
>      (Thread_Priority_node *) _Chain_First(
>        &the_thread->Priority_node.Inherited_priorities
>      )
>    );
>    _ISR_Flash( level );
> }
> _ISR_Enable( level );
>

I think Sebastian is right. There is a small window.

>
> --
> Sebastian Huber, embedded brains GmbH
>
> Address : Dornierstr. 4, D-82178 Puchheim, Germany
> Phone   : +49 89 189 47 41-16
> Fax     : +49 89 189 47 41-09
> E-Mail  : sebastian.huber at embedded-brains.de
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>
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