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changeset 17951:6a0ad2977919

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8039042: G1: Phantom zeros in cardtable Reviewed-by: tschatzl, mgerdin
author pliden
date Tue, 20 May 2014 10:24:30 +0200
parents 8a140676873f
children 09619752c16d
files src/share/vm/gc_implementation/g1/g1SATBCardTableModRefBS.cpp
diffstat 1 files changed, 9 insertions(+), 1 deletions(-) [+]
line wrap: on
line diff
--- 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