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From: John Max Skaller (skaller_at_[hidden])
Date: 2001-08-14 16:42:06

Alexander Terekhov wrote:

> could you please explain what is wrong with the following
> design of e.g. win32-like recursive mutex using TSD/TLS
> (usefulness/correctness of recursive locking aside):
> given:
> key - tsd key (or sub-key)
> lock - mutex/bin.semaphore (non-recursive lock)
> nCount - int

        I presume 'tsd' means 'thread shared data'.
In which case, I claim first a better design is to
_pass_ each thread a pointer to the shared object.

> init {
> tsd::init( &key );

        This call is clearly not typesafe:
again, I presume it takes a void *. argument.
If you pass to the thread a pointer to a
data structure such as

        struct shared {
                int key;

or whaetever, then you can initialise the key
in a typesafe manner. Furthermore, by sharing
objects between _groups_ of threads, you can
control which groups share with each other,
and which are indepedent. That is, the design
is both unsafe and inflexible, whereas passing
a pointer to each thread explicitly is typesafe
and flexible.

But perhaps I misunderstood, so please explain
if that is so (quite possible!)

John (Max) Skaller, mailto:skaller_at_[hidden] 
10/1 Toxteth Rd Glebe NSW 2037 Australia voice: 61-2-9660-0850
New generation programming language Felix
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