Branch: Tag:


2002-10-01 15:50:11 by Martin Stjernholm <>

Added some blurbs which discusses the incorrect uses of the
Thread.Condition variables and why those aren't severe bugs.

Rev: server/base_server/roxen.pike:1.806

6:   // Per Hedbor, Henrik Grubbström, Pontus Hagland, David Hedbor and others.   // ABS and suicide systems contributed freely by Francesco Chemolli    - constant cvs_version="$Id: roxen.pike,v 1.805 2002/10/01 14:37:17 anders Exp $"; + constant cvs_version="$Id: roxen.pike,v 1.806 2002/10/01 15:50:11 mast Exp $";      // The argument cache. Used by the image cache.   ArgCache argcache;
500: Inside #if defined(THREADS)
  //! Thread.Queue lookalike, which uses some archaic and less   //! known features of the preempting algorithm in pike to optimize the   //! read function. + // + // If those archaic and less known features are to depend on the + // interpreter lock in the while loop that waits on the condition + // variable then it doesn't work since Pike always might yield before + // a function call (specifically, the wait() call in the condition + // variable). Thus a handler thread might wait even though there is a + // request to process. However, the only effect is that that specific + // request isn't serviced timely; when the next request comes in the + // thread will be woken up and both requests will be handled. + // Furthermore it's extremely rare in the first place since there + // normally are several handler threads.   {    inherit Thread.Condition : r_cond;    array buffer=allocate(8);
671: Inside #if defined(THREADS)
     static int num_hold_messages;   static Thread.Condition hold_wakeup_cond = Thread.Condition(); + // Note: There are races in the use of this condition variable, but + // the only effect of that is that some handler thread might be + // considered hung when it's actually waiting on hold_wakeup_cond, and + // the hold/release handler threads function deal with hung threads + // anyway. The outcome would only be that release_handler_threads + // starts some extra handler thread unnecessarily.      void hold_handler_threads()   //! Tries to put all handler threads on hold, but gives up if it takes