ghc/runtime/main/Select.lc

   1 %
   2 % (c) The AQUA Project, Glasgow University, 1995
   3 %
   4 %************************************************************************
   5 %*                                                                      *
   6 \section[Select.lc]{Select Available File Descriptors}
   7 %*                                                                      *
   8 %************************************************************************
   9
  10 \begin{code}
  11
  12 #ifdef CONCURRENT
  13
  14 /* #define STK_CHK_DEBUG */
  15
  16 #define NULL_REG_MAP
  17 #define NON_POSIX_SOURCE
  18 /* Should there be a POSIX alternative based on poll()? */
  19 #include "stgdefs.h"
  20
  21 # if defined(HAVE_SYS_TYPES_H)
  22 #  include <sys/types.h>
  23 # endif
  24
  25 # ifdef HAVE_SYS_TIME_H
  26 #  include <sys/time.h>
  27 # endif
  28
  29 void
  30 AwaitEvent(I_ delta)
  31 {
  32     P_ tso, prev, next;
  33     rtsBool ready;
  34     fd_set rfd;
  35     I_ us;
  36     I_ min;
  37     I_ maxfd=0;
  38     struct timeval tv;
  39
  40     min = delta == 0 ? 0x7fffffff : 0;
  41
  42     /*
  43      * Collect all of the fd's that we're interested in, and capture
  44      * the minimum waiting time for the delayed threads.
  45      *
  46      * (I_)TSO_EVENT(tso) < 0 => thread waiting on fd (-(I_)TSO_EVENT(tso))
  47      *
  48      */
  49     FD_ZERO(&rfd);
  50     for(tso = WaitingThreadsHd; tso != Nil_closure; tso = TSO_LINK(tso)) {
  51         us = (I_) TSO_EVENT(tso);
  52         if (us > 0) {
  53             /* Looking at a delay event */
  54             if (us < min)
  55                 min = us;
  56         } else {
  57             /* Looking at a wait event */
  58             maxfd = ((-us)> maxfd) ? (-us) : maxfd;
  59             FD_SET((-us), &rfd);
  60         }
  61     }
  62
  63     /* Check for any interesting events */
  64
  65     tv.tv_sec = min / 1000000;
  66     tv.tv_usec = min % 1000000;
  67
  68     while (select((maxfd==0 ? 0 : (maxfd+1)), &rfd, NULL, NULL, &tv) < 0) {
  69         if (errno != EINTR) {
  70             fflush(stdout);
  71             fprintf(stderr, "AwaitEvent: select failed\n");
  72             EXIT(EXIT_FAILURE);
  73         }
  74     }
  75
  76     if (delta == 0)
  77         delta=min;
  78
  79     prev = NULL;
  80     for(tso = WaitingThreadsHd; tso != Nil_closure; tso = next) {
  81         next = TSO_LINK(tso);
  82         us = (I_) TSO_EVENT(tso);
  83         if (us > 0) {
  84             /* Looking at a delay event */
  85             us -= delta;
  86             ready = (us <= 0);
  87             if (!ready)
  88                 TSO_EVENT(tso) = (W_) us;
  89         } else {
  90             /* Looking at a wait event */
  91             ready = FD_ISSET((-us), &rfd);
  92         }
  93         if (ready) {
  94
  95 #if defined(GRAN)
  96             if (ThreadQueueTl == Nil_closure)
  97                 ThreadQueueHd = tso;
  98             else
  99                 TSO_LINK(ThreadQueueTl) = tso;
 100             ThreadQueueTl = tso;
 101             TSO_LINK(tso) = Nil_closure;
 102 #else
 103             if (RunnableThreadsTl == Nil_closure)
 104                 RunnableThreadsHd = tso;
 105             else
 106                 TSO_LINK(RunnableThreadsTl) = tso;
 107             RunnableThreadsTl = tso;
 108             TSO_LINK(tso) = Nil_closure;
 109 #endif
 110         } else {
 111             if (prev == NULL)
 112                 WaitingThreadsHd = tso;
 113             else
 114                 TSO_LINK(prev) = tso;
 115             prev = tso;
 116         }
 117     }
 118     if (prev == NULL)
 119         WaitingThreadsHd = WaitingThreadsTl = Nil_closure;
 120     else {
 121         TSO_LINK(prev) = Nil_closure;
 122         WaitingThreadsTl = prev;
 123     }
 124 }
 125
 126 #endif /* CONCURRENT */
 127 \end{code}