From: Tanaka Akira <akr@...17n.org>
Date: 2002-05-30T10:15:11+09:00
Subject: [ruby-dev:17223] race condition on Queue#pop?

$B$J$s$H$J$/(B thread.rb $B$rD/$a$F$$$F!"(BQueue#pop $B$K(B race condition $B$,$"$k(B
$B$N$G$O$J$$$+$H$$$&5$$,$7$F$-$^$7$?!#(B

Queue#pop $B$O(B

  def pop(non_block=false)
    Thread.critical = true
    begin
      loop do
       if @que.empty?
          if non_block
            raise ThreadError, "queue empty"
          end
          @waiting.push Thread.current
          Thread.stop
        else
          return @que.shift
        end
      end
    ensure
      Thread.critical = false
    end
  end

$B$H$$$&%3!<%I$G!"$"$k%9%l%C%I(B A $B$,(B pop $B$r8F$S=P$7!":G=i$K(B @que $B$,6u$@$C(B
$B$?>l9g!"$$$C$?$s(B Thread.stop $B$G;_$^$k$o$1$G$9$,!"(B($BB>$N%9%l%C%I(B B $B$,(B
Queue#push $B$r8F$S=P$7$?7k2L(B)$B:F3+$7$?;~$K$O(B Thread.critical $B$O(B false $B$K(B
$B$J$C$F$$$k$O$:$G$9!#(B

$B=>$C$F!"%k!<%W$N(B 2$B2s$jL\$G!"(B@que.empty? $B$ND>8e$K%9%l%C%I$N%3%s%F%-%9%H(B
$B%9%$%C%A$,5/$3$k2DG=@-$,$"$k$h$&$K;W$$$^$9!#$=$N%?%$%_%s%0$GB>$N(B ($B>e5-(B
$B$N(B Queue#push $B$r8F$S=P$7$?$b$N$H$O0[$J$k%9%l%C%I(B C $B$,(B) Queue#pop $B$r8F(B
$B$S=P$9$H!"(B@que $B$,6u$K$J$j!"$5$i$K%9%l%C%I(B A $B$K%3%s%F%-%9%H%9%$%C%A$7$F(B
$B=hM}$rB3$1$k$H6u$N(B @que $B$r(B shift $B$9$k$3$H$K$J$j!"(Bnil $B$,JV$jCM$K$J$k5$(B
$B$,$7$^$9!#(B

$B;DG0$J$,$i!"$3$NLdBj$rH/8=$5$;$k%F%9%H%9%/%j%W%H$r:n$k$3$H$O$G$-$^$;$s(B
$B$G$7$?$,!"$3$N$h$&$J$3$H$,$*$-$J$$J]>Z$O$I$3$+$K$"$k$G$7$g$&$+(B?
$B$b$7!"J]>Z$G$-$J$$$J$i!"<!$N$h$&$J%Q%C%A$rEv$F$k$H$$$$$s$8$c$J$$$+$H;W(B
$B$$$^$9!#(B

Index: lib/thread.rb
===================================================================
RCS file: /src/ruby/lib/thread.rb,v
retrieving revision 1.12
diff -u -r1.12 thread.rb
--- lib/thread.rb	2002/05/29 05:20:39	1.12
+++ lib/thread.rb	2002/05/30 01:02:19
@@ -182,6 +182,7 @@
 	  end
 	  @waiting.push Thread.current
 	  Thread.stop
+	  Thread.critical = true
 	else
 	  return @que.shift
 	end

$B$A$J$_$K!"(Breturn @que.shift $B$ND>A0$K(B sleep 1 unless Thread.critical $B$H(B
$B$$$&%3!<%I$rF~$l$l$P!"LdBj$rH/8=$5$;$k$3$H$,$G$-$^$7$?!#(B
-- 
[$BEDCf(B $BE/(B][$B$?$J$+(B $B$"$-$i(B][Tanaka Akira]
$B!V$U$($m(B! $B$o$+$a$A$c$s:n@o$G$9$(C"=$B!W(B(Little Worker, $B7KM7@84](B)