William "Chops" Westfield escreveu:
> On Jun 13, 2009, at 1:50 PM, Isaac Marino Bavaresco wrote:
>
>   =

>>> In general, I would not expect ANY functions in a normal PIC C  =

>>> library
>>> to be reenterant (multi-threading safe) unless explicitly documented
>>> to be so;
>>>       =

>
>   =

>> The problem may arise for functions that deal with the control
>> registers, which have fixed addresses and FreeRTOS doesn't save/ =

>> restore.
>>     =

>
> I'd expect the problems to be most likely to show up when global data  =

> structures (like buffers for a serial port) are involved.   Typical  =

> buffer code like:
>     txbuffer[outptr++] =3D char;
> wont normally contain primitives to protect them against some other  =

> process doing the same thing at the same time.  And it must, if the OS  =

> is really preemptive.
>
> BillW
>   =


This is basic, usually the designer must ensure only one task uses each
resource (serial port, etc.) at any given time (just one task use each
resource ever or using a mutex/open, close, etc.).

Even when just one task uses a resource but for instance the task fills
the buffer and an interrupt empties it, the designer must encapsulate
the accesses inside critical sections.

Regards,

Isaac

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