libgo/runtime/go-note.c

   1 /* go-note.c -- implement notesleep, notewakeup and noteclear.
   2
   3    Copyright 2009 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 /* A note is a one-time notification.  noteclear clears the note.
   8    notesleep waits for a call to notewakeup.  notewakeup wakes up
   9    every thread waiting on the note.  */
  10
  11 #include "go-assert.h"
  12 #include "runtime.h"
  13
  14 /* We use a single global lock and condition variable.  It would be
  15    better to use a futex on Linux.  */
  16
  17 static pthread_mutex_t note_lock = PTHREAD_MUTEX_INITIALIZER;
  18 static pthread_cond_t note_cond = PTHREAD_COND_INITIALIZER;
  19
  20 /* noteclear is called before any calls to notesleep or
  21    notewakeup.  */
  22
  23 void
  24 noteclear (Note* n)
  25 {
  26   int32 i;
  27
  28   i = pthread_mutex_lock (&note_lock);
  29   __go_assert (i == 0);
  30
  31   n->woken = 0;
  32
  33   i = pthread_mutex_unlock (&note_lock);
  34   __go_assert (i == 0);
  35 }
  36
  37 /* Wait until notewakeup is called.  */
  38
  39 void
  40 notesleep (Note* n)
  41 {
  42   int32 i;
  43
  44   i = pthread_mutex_lock (&note_lock);
  45   __go_assert (i == 0);
  46
  47   while (!n->woken)
  48     {
  49       i = pthread_cond_wait (&note_cond, &note_lock);
  50       __go_assert (i == 0);
  51     }
  52
  53   i = pthread_mutex_unlock (&note_lock);
  54   __go_assert (i == 0);
  55 }
  56
  57 /* Wake up every thread sleeping on the note.  */
  58
  59 void
  60 notewakeup (Note *n)
  61 {
  62   int32 i;
  63
  64   i = pthread_mutex_lock (&note_lock);
  65   __go_assert (i == 0);
  66
  67   n->woken = 1;
  68
  69   i = pthread_cond_broadcast (&note_cond);
  70   __go_assert (i == 0);
  71
  72   i = pthread_mutex_unlock (&note_lock);
  73   __go_assert (i == 0);
  74 }