[lwip-devel] [task #7212] Add Mutex concept in sys_arch

[Jonathan Larmour]

Follow-up Comment #7, task #7212 (project lwip):

> Perhaps it need an explain. In fact, my design choice answers to
> several contraints of my platform, and my first release was
> based on a IT which directly pass packets, with a
> SYS_ARCH_PROTECT based on disable interrupts. But, in my case,
> interrupts have to be really short to have no impact on the
> global performance of the system due to cache management (it's a
> DSP, and there is some tasks which have to be less interrupted as 
> possible, and the network sub system is not the one with the
> higher priority, disable interrupts give my stalls delays I have
> to reduce). That's why in my case, my system got a better
> performance with this design than with the one you find better
> for eCos port. But, this is another subject of course, and such
> design choice depend of the target to my point of view. 

Sure, that makes sense. In fact with eCos SYS_ARCH_PROTECT only disables
tasking, it doesn't disable interrupts. This is enough to stop any re-entrancy
(given how the ethernet devices work), but high priority interrupts can still
operate.

Anyway, for others, that is not the way they could do it, and adding another
thread would be worse for memory use. Adding mutex locks into the memp/pbuf
code will force them to.

Maybe Simon's suggestion is the best compromise (although there also needs to
be something to match SYS_ARCH_DECL_PROTECT, and to declare the mutex).


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