From: Simon Marlow <simonmar@microsoft.com>
Date: Thu, 9 Feb 2006 12:30:56 +0000 (+0000)
Subject: improvement to the deadlock detection
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=7b2ff4cc95ce49081d84c25184aec796377fbc35;p=ghc-hetmet.git

improvement to the deadlock detection

When the RTS is idle, as detected by the timer signal, instead of
prodding capabilities from the signal handler (which is not guaranteed
to work - pthread_cond_signal() can't be called from signal handlers),
create a new thread to do it.
---

diff --git a/ghc/rts/Timer.c b/ghc/rts/Timer.c
index b6414f8..425ada5 100644
--- a/ghc/rts/Timer.c
+++ b/ghc/rts/Timer.c
@@ -21,6 +21,7 @@
 #include "Timer.h"
 #include "Ticker.h"
 #include "Capability.h"
+#include "OSThreads.h"
 
 /* ticks left before next pre-emptive context switch */
 static int ticks_to_ctxt_switch = 0;
@@ -30,6 +31,10 @@ static int ticks_to_ctxt_switch = 0;
 static int ticks_to_gc = 0;
 #endif
 
+#if defined(THREADED_RTS)
+static void OSThreadProcAttr proddingThread(void *p);
+#endif
+
 /*
  * Function: handle_tick()
  *
@@ -60,7 +65,8 @@ handle_tick(int unused STG_UNUSED)
 	      recent_activity = ACTIVITY_MAYBE_NO;
 	      ticks_to_gc = RtsFlags.GcFlags.idleGCDelayTicks;
 	      break;
-	  case ACTIVITY_MAYBE_NO:
+	  case ACTIVITY_MAYBE_NO: {
+	      OSThreadId id;
 	      if (ticks_to_gc == 0) break; /* 0 ==> no idle GC */
 	      ticks_to_gc--;
 	      if (ticks_to_gc == 0) {
@@ -69,14 +75,15 @@ handle_tick(int unused STG_UNUSED)
 		  blackholes_need_checking = rtsTrue;
 		  /* hack: re-use the blackholes_need_checking flag */
 
-		  /* ToDo: this doesn't work.  Can't invoke
-		   * pthread_cond_signal from a signal handler.
-		   * Furthermore, we can't prod a capability that we
-		   * might be holding.  What can we do?
+		  /* We can't prod the Capability from inside the
+		   * signal handler, because pthread_cond_signal()
+		   * doesn't work from signal handlers.  Let's hope
+		   * that pthread_create() works:
 		   */
-		  prodOneCapability();
+		  createOSThread(&id, proddingThread, NULL);
 	      }
 	      break;
+	  }
 	  default:
 	      break;
 	  }
@@ -85,6 +92,15 @@ handle_tick(int unused STG_UNUSED)
   }
 }
 
+#if defined(THREADED_RTS)
+static void OSThreadProcAttr
+proddingThread(void *p STG_UNUSED)
+{
+    prodOneCapability();
+    // and exit again.
+}
+#endif
+
 int
 startTimer(nat ms)
 {