[Bordeaux-threads-devel] Deprecating recursive locks

[Stelian Ionescu]

On Wed, 2012-05-02 at 13:13 -0400, James M. Lawrence wrote:
> On Wed, May 2, 2012 at 11:27 AM, Stelian Ionescu <sionescu at cddr.org> wrote:
> > On Wed, 2012-05-02 at 11:15 -0400, James M. Lawrence wrote:
> >> On Tue, Apr 17, 2012 at 11:21 AM, Stelian Ionescu <sionescu at cddr.org> wrote:
> >> > They're an ugly hack, as described their inventor David Butenhof
> >> > (http://tinyurl.com/butenhof-recursive-mutexes) and aren't supported by
> >> > all lisps: Allegro, Clozure, CMUCL, SBCL(it has a kind of recursive
> >> > lock, but it's not a posix recursive lock), so I was thinking of making
> >> > a 1.0 release in which to remove them altogether.
> >> >
> >> > What do you think ?
> >>
> >> I currently use a recursive lock for debug logging. In the past I
> >> wrapped *debugger-hook* with a recursive lock in order to avoid
> >> multiple simultaneous debugger popups. Both are cases of throwaway
> >> code.
> >>
> >> David Butenhof does mention that recursive locks "can be a great tool"
> >> as long as they are properly understood as a temporary measure. That's
> >> how I use them, and others may as well. Yes, they are a hack, but they
> >> are a convenient hack.
> >>
> >> If recursive locks are removed then I would expect people to write
> >> their own half-ass implementations, as I would do for my debug logger.
> >> I agree that using them in a non-temporary context may constitute poor
> >> design, however that does not imply that they should be removed.
> >>
> >> Perhaps adding a note to the documentation regarding the hackiness of
> >> recursive locks (and/or even linking to the Butenhof post) would
> >> suffice in lieu of outright deletion?
> >>
> >> If you do decide to remove them, consider issuing deprecation warnings
> >> in the next release (or longer) before the actual removal. There is at
> >> least one logging library in quicklisp which uses a recursive lock. I
> >> assume other projects out there would be broken as well.
> >
> > Which one ? Such library is broken because few CL implementations
> > actually have recursive locks
> 
> log4cl, released a few months ago.
> 
> You mentioned that Clozure does not support recursive locks. The funny
> thing about Clozure is that ccl:make-lock actually returns a recursive
> lock.

Indeed I was fooled by that. Good to know, this is a excellent reason
not to ever use Clozure

-- 
Stelian Ionescu a.k.a. fe[nl]ix
Quidquid latine dictum sit, altum videtur.
http://common-lisp.net/project/iolib

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