Subj : Re: recursive mutexes
To   : comp.programming.threads
From : Uenal Mutlu
Date : Wed May 18 2005 11:25 pm

"Sergei Organov" wrote
> "Uenal Mutlu" writes:
> > "Sergei Organov" wrote
> > > "Uenal Mutlu"
>
> > I'm willingly making use of its recursivity feature because it
> > simplifies many things, and most importantly it is safer than
> > non-recursive locking,
>
> It depends on the definition of "safer". For me "safer" is not equal to
> "no deadlock".

True, and nobody has said that. A recursive mutex helps only for the
current thread to not deadlock itself. But apart from this the same dangers
for deadlock exist equally for both non-recursive and recursive mutices.
If you apply my deadlock theorem then a deadlock cannot occur.
If you also want to exclude self-deadlocking then the use of
a recursive-mutex will solve even that case. What's left?

> Using my definition of "safer", the recursive lock is not
> safer due to the fact that it allows actual problems in the code to be
> hidden for a long time.

It depends whether you see the use of a recursive mutex
as a problem or not. As I said: if I use a recursive mutex then
I'm making use of its recursion feature. This then cannot
be seen as an error (but we already had discussed this case).

> > though it has a neglectable overhead. If I use a _recursive locking
> > method_ then I'm of course aware of these facts.
>
> If you were aware of the experience that has been gathered in this
> field, you won't use recursive locking method in the first place.

I respect all the old veterans, but please let us also make
some progress in the field, and not always chew the old gum..

> The recursive locks simplify your life by allowing you not to think
> about quality of your design. Kinda like favorite goto's in programming
> languages, -- they do simplify programming in the short run but the
> result is usually a wrong and unmaintainable problem^H^H^H^Hgram in the
> long run. If you consider such simplifications to be a good thing, --
> it's your problem.

I would say that it is even much easier to develop a complex system
and also much easier to maintain it by the use of recursive mutices.
Nevertheless, this seems to be a religious issue, so I do respect your
and other's view on this, but please try to respect my view and my preferance
for recursive mutices too, since I've researched this field and am a
prefessional developer with more than 15 yrs of experience, so
I too know of what I'm talking of. Besides this, I strongly believe the future
belongs to the recursive mutices for their simplicity and safety over
non-recursive mutices, esp. for the huge and complex requirements
nowadays and of the future.

.