[project @ 2003-06-26 12:22:59 by stolz]

[ghc-hetmet.git] / ghc / rts / Select.c

diff --git a/ghc/rts/Select.c b/ghc/rts/Select.c
index a2c990e..677fdd2 100644 (file)
--- a/ghc/rts/Select.c
+++ b/ghc/rts/Select.c
@@ -1,5 +1,5 @@
 /* -----------------------------------------------------------------------------
- * $Id: Select.c,v 1.21 2002/07/17 09:21:51 simonmar Exp $
+ * $Id: Select.c,v 1.29 2003/06/26 12:22:59 stolz Exp $
  *
  * (c) The GHC Team 1995-2002
  *
@@ -7,6 +7,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
+
 /* we're outside the realms of POSIX here... */
 /* #include "PosixSource.h" */
 
@@ -14,8 +15,10 @@
 #include "Schedule.h"
 #include "RtsUtils.h"
 #include "RtsFlags.h"
+#include "Timer.h"
 #include "Itimer.h"
 #include "Signals.h"
+#include "Capability.h"
 
 # ifdef HAVE_SYS_TYPES_H
 #  include <sys/types.h>
@@ -25,16 +28,23 @@
 #  include <sys/time.h>
 # endif
 
-# ifdef mingw32_TARGET_OS
-#  include <windows.h>
-# endif
-
 #include <errno.h>
 #include <string.h>
 
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
 /* last timestamp */
 nat timestamp = 0;
 
+#ifdef RTS_SUPPORTS_THREADS
+static rtsBool isWorkerBlockedInAwaitEvent = rtsFalse;
+static rtsBool workerWakeupPending = rtsFalse;
+static int workerWakeupPipe[2];
+static rtsBool workerWakeupInited = rtsFalse;
+#endif
+
 /* There's a clever trick here to avoid problems when the time wraps
  * around.  Since our maximum delay is smaller than 31 bits of ticks
  * (it's actually 31 bits of microseconds), we can safely check
@@ -84,13 +94,10 @@ awaitEvent(rtsBool wait)
     StgTSO *tso, *prev, *next;
     rtsBool ready;
     fd_set rfd,wfd;
-#ifndef mingw32_TARGET_OS
     int numFound;
     int maxfd = -1;
-#endif
     rtsBool select_succeeded = rtsTrue;
     rtsBool unblock_all = rtsFalse;
-    static rtsBool prev_unblocked_all = rtsFalse;
     struct timeval tv;
     lnat min, ticks;
 
@@ -126,7 +133,6 @@ awaitEvent(rtsBool wait)
          min = 0x7ffffff;
       }
 
-#ifndef mingw32_TARGET_OS
       /* 
        * Collect all of the fd's that we're interested in
        */
@@ -158,6 +164,15 @@ awaitEvent(rtsBool wait)
        }
       }
 
+#ifdef RTS_SUPPORTS_THREADS
+      if(!workerWakeupInited) {
+          pipe(workerWakeupPipe);
+          workerWakeupInited = rtsTrue;
+      }
+      FD_SET(workerWakeupPipe[0], &rfd);
+      maxfd = workerWakeupPipe[0] > maxfd ? workerWakeupPipe[0] : maxfd;
+#endif
+      
       /* Release the scheduler lock while we do the poll.
        * this means that someone might muck with the blocked_queue
        * while we do this, but it shouldn't matter:
@@ -170,6 +185,11 @@ awaitEvent(rtsBool wait)
        *
        * I believe none of these cases lead to trouble --SDM.
        */
+      
+#ifdef RTS_SUPPORTS_THREADS
+      isWorkerBlockedInAwaitEvent = rtsTrue;
+      workerWakeupPending = rtsFalse;
+#endif
       RELEASE_LOCK(&sched_mutex);
 
       /* Check for any interesting events */
@@ -188,12 +208,16 @@ awaitEvent(rtsBool wait)
               should we see a bad file descriptor & give the threads
               a chance to clean up their act. 
               
-              To avoid getting stuck in a loop, repeated EBADF failures
-              are 'handled' through barfing.
+              Note: assume here that threads becoming unblocked
+              will try to read/write the file descriptor before trying
+              to issue a threadWaitRead/threadWaitWrite again (==> an
+              IOError will result for the thread that's got the bad
+              file descriptor.) Hence, there's no danger of a bad
+              file descriptor being repeatedly select()'ed on, so
+              the RTS won't loop.
            */
-           if ( errno == EBADF && !prev_unblocked_all) {
+           if ( errno == EBADF ) {
              unblock_all = rtsTrue;
-             prev_unblocked_all = rtsTrue;
              break;
            } else {
              fprintf(stderr,"%d\n", errno);
@@ -202,20 +226,17 @@ awaitEvent(rtsBool wait)
              barf("select failed");
            }
          }
-#else /* on mingwin */
-      while (1) {
-         Sleep(0); /* don't busy wait */
-#endif /* mingw32_TARGET_OS */
          ACQUIRE_LOCK(&sched_mutex);
+#ifdef RTS_SUPPORTS_THREADS
+          isWorkerBlockedInAwaitEvent = rtsFalse;
+#endif
 
-         prev_unblocked_all = rtsFalse;
-
-#ifndef mingw32_TARGET_OS
          /* We got a signal; could be one of ours.  If so, we need
           * to start up the signal handler straight away, otherwise
           * we could block for a long time before the signal is
           * serviced.
           */
+#if defined(RTS_USER_SIGNALS)
          if (signals_pending()) {
              RELEASE_LOCK(&sched_mutex); /* ToDo: kill */
              startSignalHandlers();
@@ -241,6 +262,18 @@ awaitEvent(rtsBool wait)
              return; /* still hold the lock */
          }
          
+#ifdef RTS_SUPPORTS_THREADS
+         /* If another worker thread wants to take over,
+          * return to the scheduler
+          */
+         if (needToYieldToReturningWorker()) {
+             return; /* still hold the lock */
+         }
+#endif
+         
+#ifdef RTS_SUPPORTS_THREADS
+          isWorkerBlockedInAwaitEvent = rtsTrue;
+#endif
          RELEASE_LOCK(&sched_mutex);
       }
 
@@ -286,6 +319,36 @@ awaitEvent(rtsBool wait)
              blocked_queue_tl = prev;
          }
       }
-
+      
+#if defined(RTS_SUPPORTS_THREADS)
+       // if we were woken up by wakeBlockedWorkerThread,
+       // read the dummy byte from the pipe
+      if(select_succeeded && FD_ISSET(workerWakeupPipe[0], &rfd)) {
+          unsigned char dummy;
+          wait = rtsFalse;
+          read(workerWakeupPipe[0],&dummy,1);
+      }
+#endif
     } while (wait && !interrupted && run_queue_hd == END_TSO_QUEUE);
 }
+
+
+#ifdef RTS_SUPPORTS_THREADS
+/* wakeBlockedWorkerThread
+ *
+ * If a worker thread is currently blocked within awaitEvent,
+ * wake it.
+ * Must be called with sched_mutex held.
+ */
+void
+wakeBlockedWorkerThread()
+{
+    if(isWorkerBlockedInAwaitEvent && !workerWakeupPending) {
+       unsigned char dummy = 42;       // Any value will do here
+       
+                       // write something so that select() wakes up
+       write(workerWakeupPipe[1],&dummy,1);
+       workerWakeupPending = rtsTrue;
+    }
+}
+#endif