On Wed, 29 Oct 2008, Pritpal Bedi wrote:
Hi Pritpal,
> CRITICAL PROC p() is the easiest way.
It depends on context. There are situations where it cannot be used
as mutex replacement - you will end with mutex simulation using
critical function and conditional variable.
> Can it be implemented in C also? Like
> HB_FUNC_CRITICAL( SOMEFUNC )
> {
> // do sth
> }
No. At least in the above way because it cannot work. The protection
has to be external to function body because classic C does not support
any mechanism which allow to bind user code as function preamble/postamble.
Additionally we have to make it working also for pure PCODE functions
loaded from .hrb files or returned directly by our compiler.
It will be possible to mark any Harbour function written in C or as .prg
code as CRITICAL for HVM. So they will have to be registered in HVM as
critical ones.
Please also note that CRITICAL function/procedure does not give
mutual exclusion because it is called CRITICAL. It's necessary
to execute low level C code which initializes mutex and then will
lock and unlock it. Hiding these operations for .prg code gives
some sense for Harbour programmers and can simplify .prg code also
increasing the speed but in C it does not give anything more then
declaring some macros which will replace real function calls what
will not change anything in final binaries and what anyone can do
for his own use at any moment :-)
best regards,
Przemek
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