From: simonmar <unknown>
Date: Wed, 12 Oct 2005 12:58:38 +0000 (+0000)
Subject: [project @ 2005-10-12 12:58:38 by simonmar]
X-Git-Tag: Initial_conversion_from_CVS_complete~176
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=1be10360a614b6134ae5c609a148ea20a6e586e1;hp=1446bc7d943c6a92dbd48acf6a2e8fb408cdc6fb;p=ghc-hetmet.git

[project @ 2005-10-12 12:58:38 by simonmar]
DEBUG_FILL_SLOP: don't do anything on SMP, zeroing slop words isn't safe
---

diff --git a/ghc/includes/Updates.h b/ghc/includes/Updates.h
index 0d0bf2f..2685850 100644
--- a/ghc/includes/Updates.h
+++ b/ghc/includes/Updates.h
@@ -185,8 +185,13 @@ extern void awakenBlockedQueue(StgBlockingQueueElement *q, StgClosure *node);
  * to point to itself, and the closure being updated should not
  * already have been updated (the mutable list will get messed up
  * otherwise).
+ *
+ * NB. We do *not* do this in SMP mode, because when we have the
+ * possibility of multiple threads entering the same closure, zeroing
+ * the slop in one of the threads would have a disastrous effect on
+ * the other (seen in the wild!).
  */
-#if !defined(DEBUG)
+#if !defined(DEBUG) || defined(SMP)
 
 #define DEBUG_FILL_SLOP(p) /* nothing */