ghc/rts/Timer.c

   1 /* -----------------------------------------------------------------------------
   2  *
   3  * (c) The GHC Team, 1995-2005
   4  *
   5  * Interval timer service for profiling and pre-emptive scheduling.
   6  *
   7  * ---------------------------------------------------------------------------*/
   8
   9 /*
  10  * The interval timer is used for profiling and for context switching in the
  11  * threaded build.
  12  *
  13  * This file defines the platform-independent view of interval timing, relying
  14  * on platform-specific services to install and run the timers.
  15  *
  16  */
  17 #include "Rts.h"
  18 #include "RtsFlags.h"
  19 #include "Proftimer.h"
  20 #include "Schedule.h"
  21 #include "Timer.h"
  22 #include "Ticker.h"
  23 #include "Capability.h"
  24 #include "OSThreads.h"
  25
  26 /* ticks left before next pre-emptive context switch */
  27 static int ticks_to_ctxt_switch = 0;
  28
  29 #if defined(THREADED_RTS)
  30 /* idle ticks left before we perform a GC */
  31 static int ticks_to_gc = 0;
  32 #endif
  33
  34 #if defined(THREADED_RTS)
  35 static void OSThreadProcAttr proddingThread(void *p);
  36 #endif
  37
  38 /*
  39  * Function: handle_tick()
  40  *
  41  * At each occurrence of a tick, the OS timer will invoke
  42  * handle_tick().
  43  */
  44 static
  45 void
  46 handle_tick(int unused STG_UNUSED)
  47 {
  48 #ifdef PROFILING
  49   handleProfTick();
  50 #endif
  51   if (RtsFlags.ConcFlags.ctxtSwitchTicks > 0) {
  52       ticks_to_ctxt_switch--;
  53       if (ticks_to_ctxt_switch <= 0) {
  54           ticks_to_ctxt_switch = RtsFlags.ConcFlags.ctxtSwitchTicks;
  55           context_switch = 1;   /* schedule a context switch */
  56
  57 #if defined(THREADED_RTS)
  58           /*
  59            * If we've been inactive for idleGCDelayTicks (set by +RTS
  60            * -I), tell the scheduler to wake up and do a GC, to check
  61            * for threads that are deadlocked.
  62            */
  63           switch (recent_activity) {
  64           case ACTIVITY_YES:
  65               recent_activity = ACTIVITY_MAYBE_NO;
  66               ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  67               break;
  68           case ACTIVITY_MAYBE_NO: {
  69               OSThreadId id;
  70               if (ticks_to_gc == 0) break; /* 0 ==> no idle GC */
  71               ticks_to_gc--;
  72               if (ticks_to_gc == 0) {
  73                   ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
  74                   recent_activity = ACTIVITY_INACTIVE;
  75                   blackholes_need_checking = rtsTrue;
  76                   /* hack: re-use the blackholes_need_checking flag */
  77
  78                   /* We can't prod the Capability from inside the
  79                    * signal handler, because pthread_cond_signal()
  80                    * doesn't work from signal handlers.  Let's hope
  81                    * that pthread_create() works:
  82                    */
  83                   createOSThread(&id, proddingThread, NULL);
  84               }
  85               break;
  86           }
  87           default:
  88               break;
  89           }
  90 #endif
  91       }
  92   }
  93 }
  94
  95 #if defined(THREADED_RTS)
  96 static void OSThreadProcAttr
  97 proddingThread(void *p STG_UNUSED)
  98 {
  99     prodOneCapability();
 100     // and exit again.
 101 }
 102 #endif
 103
 104 int
 105 startTimer(nat ms)
 106 {
 107 #ifdef PROFILING
 108   initProfTimer();
 109 #endif
 110
 111   return startTicker(ms, handle_tick);
 112 }
 113
 114 int
 115 stopTimer()
 116 {
 117   return stopTicker();
 118 }