Re: [Chicken-janitors] #989: High CPU usage when calling signal handler multiple times

[Chicken Trac]

#989: High CPU usage when calling signal handler multiple times
-----------------------------+----------------------------------------------
  Reporter:  mario           |       Owner:                 
      Type:  defect          |      Status:  new            
  Priority:  critical        |   Milestone:  4.9.0          
 Component:  core libraries  |     Version:  4.8.x          
Resolution:                  |    Keywords:  signal handling
-----------------------------+----------------------------------------------

Comment(by sjamaan):

 Still unclear, but the continuation of sleep seems to be doing something
 very strange. If we explicitly capture the continuation (which should be
 identical to the implicit continuation) and pass it to the procedure when
 we invoke it, it works.  If we use the continuation supplied by the
 foreign-lambda wrapper, it breaks.

 However, if sleep(x) is replaced by a constant integer, it works with
 either continuation.

 {{{
 #!scm
 (use posix)

 ;; BROKEN:
 (define do-sleep
   (foreign-primitive ((scheme-object k) (int x))
                      "printf(\"%d\\n\", sleep(x)); C_values(2,
 C_SCHEME_UNDEFINED, C_k);"))

 ;; OKAY:
 (define do-sleep
   (foreign-primitive ((scheme-object k) (int x))
                      "printf(\"%d\\n\", sleep(x)); C_values(2,
 C_SCHEME_UNDEFINED, k);"))


 (set-signal-handler!
  signal/int
  (lambda (signal)
    (print "caught signal" signal)
    (call/cc (lambda (k) (do-sleep k 10)))))


 (let loop ()
   (sleep 1)
   (loop))
 }}}

 It gets weirder and weirder!

-- 
Ticket URL: <http://bugs.call-cc.org/ticket/989#comment:6>
Chicken Scheme <http://www.call-with-current-continuation.org/>
Chicken Scheme is a compiler for the Scheme programming language.