Re: [lwip-users] Wait queue order for mutex, semaphore, mailbox?

[address@hidden]

Am 11.11.2021 um 21:46 schrieb Grant Edwards:
> On 2021-11-11, goldsimon@gmx.de <goldsimon@gmx.de> wrote:
> > Am 11.11.2021 um 17:36 schrieb Grant Edwards:
> > > What should the wait queue order be for lwIP mailboxes, mutexes, and
> > > semaphores?
> > >
> > > The port I'm trying to fix-up and get running is configuring all for
> > > FIFO wait queues.
> >
> > I'm not sure I understand your question. Do you mean 'if multiple
> > threads are waiting, which one gets woken first'?
>
> Yes.
>
> > In that case, it's nothing we as lwIP developers can answer:
>
> But they're the ones that actually know what those kernel objects are
> used for.

"for": yes. But to me, your "FIFO or priority" question is a performance
question: the core of lwIP is not really using those objects (in the way
you want to know about), only the application threads using sockets etc.

> > it's mainly a question of how you want your system to behave. Using
> > a decent embedded RTOS, I would say the answer is "the thread with
> > the highest priority should be woken first", but that's really up to
> > how your OS shall behave.
>
> So the lwIP stack will work correctly with either FIFO or priority
> queueing for the kernel objects used internally by lwIP?

Yes, the only impact I can see is performance: using a FIFO mechanism,
you will probably not be able to implement a true priority based thread
system.

Regards,
Simon