# HG changeset patch
# User pliden
# Date 1400574270 -7200
# Node ID 6a0ad297791984e3d0794c3a87b97edc248d3751
# Parent  8a140676873f3f91ecec53e0e2c2d518006f5e1a
8039042: G1: Phantom zeros in cardtable
Reviewed-by: tschatzl, mgerdin

diff -r 8a140676873f -r 6a0ad2977919 src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp
--- a/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	Wed May 14 14:32:23 2014 +0200
+++ b/src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp	Tue May 20 10:24:30 2014 +0200
@@ -95,7 +95,15 @@
   jbyte *const first = byte_for(mr.start());
   jbyte *const last = byte_after(mr.last());
 
-  memset(first, g1_young_gen, last - first);
+  // Below we may use an explicit loop instead of memset() because on
+  // certain platforms memset() can give concurrent readers phantom zeros.
+  if (UseMemSetInBOT) {
+    memset(first, g1_young_gen, last - first);
+  } else {
+    for (jbyte* i = first; i < last; i++) {
+      *i = g1_young_gen;
+    }
+  }
 }
 
 #ifndef PRODUCT