ghc/rts/win32/AwaitEvent.c

   1 /*
   2  * Wait/check for external events. Periodically, the
   3  * Scheduler checks for the completion of external operations,
   4  * like the expiration of timers, completion of I/O requests
   5  * issued by Haskell threads.
   6  *
   7  * If the Scheduler is otherwise out of work, it'll block
   8  * herein waiting for external events to occur.
   9  *
  10  * This file mirrors the select()-based functionality
  11  * for POSIX / Unix platforms in rts/Select.c, but for
  12  * Win32.
  13  *
  14  */
  15 #include "Rts.h"
  16 #include "Schedule.h"
  17 #include <windows.h>
  18 #include "win32/AsyncIO.h"
  19 #if defined(RTS_SUPPORTS_THREADS)
  20 #include "Capability.h"
  21 #endif
  22
  23 void
  24 awaitEvent(rtsBool wait)
  25 {
  26   RELEASE_LOCK(&sched_mutex);
  27   do {
  28     /* Try to de-queue completed IO requests */
  29     if (!awaitRequests(wait)) {
  30       return;
  31     }
  32     ACQUIRE_LOCK(&sched_mutex);
  33     /* we were interrupted, return to the scheduler immediately.
  34      */
  35     if (interrupted) {
  36       return; /* still hold the lock */
  37     }
  38
  39     /* If new runnable threads have arrived, stop waiting for
  40      * I/O and run them.
  41      */
  42     if (run_queue_hd != END_TSO_QUEUE) {
  43       return; /* still hold the lock */
  44     }
  45
  46 #ifdef RTS_SUPPORTS_THREADS
  47     /* If another worker thread wants to take over,
  48      * return to the scheduler
  49      */
  50     if (needToYieldToReturningWorker()) {
  51       return; /* still hold the lock */
  52     }
  53 #endif
  54     RELEASE_LOCK(&sched_mutex);
  55   } while (wait && !interrupted && run_queue_hd == END_TSO_QUEUE);
  56 }
  57
  58 #ifdef RTS_SUPPORTS_THREADS
  59 void
  60 wakeBlockedWorkerThread()
  61 {
  62   abandonRequestWait();
  63 }
  64 #endif
  65