Ludovic Courtès escreveu: > Hello, > > Andy Wingo <[EMAIL PROTECTED]> writes: > >> ERROR: srfi-18.test: thread-start!: >> thread activates only after start >> - arguments: ((syntax-error "memoization" >> "In file ~S, line ~S: ~A ~S in expression ~S." >> ("/home/lilydev/vc/guile/srfi/srfi-18.scm" 135 >> "Bad binding" ct >> (let (ct (current-thread)) >> [EMAIL PROTECTED] (or (hashq-ref >> thread-exception-handlers ct) >> (hashq-set! thread-exception-handlers ct >> (list initial-handler))))) #f)) > > I'm seeing this as well, but it's a [EMAIL PROTECTED]' here (single-binding > `let's > are memoized as [EMAIL PROTECTED]'): > > ((syntax-error "memoization" > "In file ~S, line ~S: ~A ~S in expression ~S." > ("/home/ludo/src/guile/srfi/srfi-18.scm" 138 > "Bad binding" > ct > ([EMAIL PROTECTED] (ct (#<variable b7d28110 value: > #<primitive-procedure current-thread>>)) > ([EMAIL PROTECTED] (#<variable b7d2ad88 value: > #<primitive-procedure hashq-ref>> > #<variable 839df08 value: > #<weak-key-hash-table 1/31>> [EMAIL PROTECTED]) > (#<variable b7d2adc0 value: #<primitive-procedure > hashq-set!>> #<variable 839df08 value: #<weak-key-hash-table 1/31>> [EMAIL > PROTECTED] (#<variable b7d2c498 value: #<primitive-procedure list>> > #<variable 839d130 value: #<procedure initial-handler (obj)>>)) > ))) > #f)) > > It can be reproduced, but very infrequently, with this program: > > (use-modules (ice-9 threads)) > > (define (foo x y) > (let ((z (+ x y))) > (let ((a (+ z 1))) > (let ((b (- a 2))) > (let ((c (* b 3))) > c))))) > > (define (entry) > (foo 1 2)) > > (for-each (lambda (i) (make-thread entry)) > (iota 123)) > > My explanation is that the `let*' memoizer, aka. `scm_m_letstar ()', is > not thread-safe; it's clearly not atomic, and it's of course not > protected by a mutex or so.
Is that the only one? SCM scm_m_let (SCM expr, SCM env) ... /* plain let */ SCM rvariables; SCM inits; transform_bindings (bindings, expr, &rvariables, &inits); { const SCM new_body = m_body (SCM_IM_LET, SCM_CDR (cdr_expr)); const SCM new_tail = scm_cons2 (rvariables, inits, new_body); SCM_SETCAR (expr, SCM_IM_LET); // ****!!! SCM_SETCDR (expr, new_tail); What happens if another thread tries to evaluate expr at the place marked ****!!! ? At the very least, we should have an atomic SCM_SETCELL() which overwrites car and cdr atomically. -- Han-Wen Nienhuys - [EMAIL PROTECTED] - http://www.xs4all.nl/~hanwen