SBCL just changed the fasl file version, so I need to rebuild CLX and#

Sat Jul 19 00:35:28 2003

SBCL just changed the fasl file version, so I need to rebuild CLX and McCLIM. While it chugs away it might be time for some notes on McCLIM Day 2, except that there's practically no difference from day 1. I created a class for account, and a presentation type which presents as an account name. Then I decided to tackle some of the bugs

• The pg problem was that it was doing something akin to

  (handler-case 
      (foo) 
    (error (e) 
      (cleanup forms)
      (signal e)))
  

  Notice that the error is resignalled with signal instead of error. The difference between the two is that error will enter the debugger if the condition e is not handled, whereas signal will keep quiet and pretend nothing happened. I rewrote this to use an unwind-protect form instead.
• Spent some time looking at backtraces to decide where the periodic hangs were coming from. After deciding the bug was in SBCL itself, spent even more time staring hard at the queueing functions. Then rewrite them to have less obvious race conditions. I don't claim it's necessarily correct now, but I haven't managed to break it yet. It's probably slower. It might be detectably slower; it seemed to be quite slow when I was testing it, but I might have been imagining that. Or it migt have been swapping. This machine is usually swapping, after all. Anyway, changes committed, will be in 0.8.2 at the end of the month

I'm not going to cry too hard about the slowdown at the moment, because McCLIM has native-threads-unfriendly queuing, and the effect of that on top of the CLX native-threads-unfriendly thread synchronisation primitives means that there should be some fairly significant speedups to be made that don't involve staring at sbcl disassembly. In fact, as low-hanging fruit goes, I think that if we park the wheelbarrow underneath the tree and shake gently, this stuff wouldn't even fall far enough to bruise.

;;; from CLX
#+sbcl
(defvar *without-interrupts-sic-lock*
  (sb-thread:make-mutex :name "lock simulating *without-interrupts*"))
#+sbcl
(defmacro without-interrupts (&body body)
  `(sb-thread:with-recursive-lock (*without-interrupts-sic-lock*)
    ,@body))

;;; from McCLIM
(defmacro atomic-incf (place)
  `(sb-thread::with-spinlock (xlib::*conditional-store-queue*)
    (incf ,place)))

You get the idea