workbench/libs/thread/broadcastcondition.c

   1 /*
   2  * thread.library - threading and synchronisation primitives
   3  *
   4  * Copyright © 2007 Robert Norris
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the same terms as AROS itself.
   8  */
   9
  10 #include "thread_intern.h"
  11
  12 #include <exec/tasks.h>
  13 #include <exec/lists.h>
  14 #include <proto/exec.h>
  15 #include <assert.h>
  16
  17 /*****************************************************************************
  18
  19     NAME */
  20         AROS_LH1(void, BroadcastCondition,
  21
  22 /*  SYNOPSIS */
  23         AROS_LHA(void *, cond, A0),
  24
  25 /*  LOCATION */
  26         struct ThreadBase *, ThreadBase, 19, Thread)
  27
  28 /*  FUNCTION
  29         Signals all threads waiting on a condition variable.
  30
  31     INPUTS
  32         cond - the condition to signal.
  33
  34     RESULT
  35         This function always succeeds.
  36
  37     NOTES
  38         Before calling this function you should lock the mutex that protects
  39         the condition. WaitCondition() atomically unlocks the mutex and waits
  40         on the condition, so by locking the mutex first before sending the
  41         signal, you ensure that the signal cannot be missed. See
  42         WaitCondition() for more details.
  43
  44         If no threads are waiting on the condition, nothing happens.
  45
  46     EXAMPLE
  47         LockMutex(mutex);
  48         BroadcastCondition(cond);
  49         UnlockMutex(mutex);
  50
  51     BUGS
  52
  53     SEE ALSO
  54         CreateCondition(), DestroyCondition(), WaitCondition(),
  55         SignalCondition()
  56
  57     INTERNALS
  58         SIGF_SIGNAL is used to signal the selected waiting thread.
  59
  60 *****************************************************************************/
  61 {
  62     AROS_LIBFUNC_INIT
  63
  64     struct _Condition *c = (struct _Condition *) cond;
  65     struct _CondWaiter *waiter;
  66
  67     assert(c != NULL);
  68
  69     /* safely operation on the condition */
  70     ObtainSemaphore(&c->lock);
  71
  72     /* wake up all the waiters */
  73     while ((waiter = (struct _CondWaiter *) REMHEAD(&c->waiters)) != NULL) {
  74         Signal(waiter->task, SIGF_SINGLE);
  75         FreeMem(waiter, sizeof(struct _CondWaiter));
  76     }
  77
  78     /* none left */
  79     c->count = 0;
  80
  81     ReleaseSemaphore(&c->lock);
  82
  83     AROS_LIBFUNC_EXIT
  84 } /* BroadcastCondition */