changeset 39451:19cd3b995de9

8148813: Windows os::check_heap needs more information Summary: added ring buffer to log info while walking the heap Reviewed-by: mgronlun, dholmes, ccheung
author iklam
date Sun, 26 Jun 2016 20:00:45 -0700
parents 78e99b030d5f
children eebe070746ad
files hotspot/src/os/windows/vm/os_windows.cpp
diffstat 1 files changed, 22 insertions(+), 1 deletions(-) [+]
line wrap: on
line diff
--- a/hotspot/src/os/windows/vm/os_windows.cpp	Fri Jun 24 15:09:00 2016 -0700
+++ b/hotspot/src/os/windows/vm/os_windows.cpp	Sun Jun 26 20:00:45 2016 -0700
@@ -5250,6 +5250,12 @@
 
 static int mallocDebugIntervalCounter = 0;
 static int mallocDebugCounter = 0;
+
+// For debugging possible bugs inside HeapWalk (a ring buffer)
+#define SAVE_COUNT 8
+static PROCESS_HEAP_ENTRY saved_heap_entries[SAVE_COUNT];
+static int saved_heap_entry_index;
+
 bool os::check_heap(bool force) {
   if (++mallocDebugCounter < MallocVerifyStart && !force) return true;
   if (++mallocDebugIntervalCounter >= MallocVerifyInterval || force) {
@@ -5270,13 +5276,28 @@
     if (HeapLock(heap) != 0) {
       PROCESS_HEAP_ENTRY phe;
       phe.lpData = NULL;
+      memset(saved_heap_entries, 0, sizeof(saved_heap_entries));
+      saved_heap_entry_index = 0;
+      int count = 0;
+
       while (HeapWalk(heap, &phe) != 0) {
+        count ++;
         if ((phe.wFlags & PROCESS_HEAP_ENTRY_BUSY) &&
             !HeapValidate(heap, 0, phe.lpData)) {
           tty->print_cr("C heap has been corrupted (time: %d allocations)", mallocDebugCounter);
-          tty->print_cr("corrupted block near address %#x, length %d", phe.lpData, phe.cbData);
+          tty->print_cr("corrupted block near address %#x, length %d, count %d", phe.lpData, phe.cbData, count);
           HeapUnlock(heap);
           fatal("corrupted C heap");
+        } else {
+          // Save previous seen entries in a ring buffer. We have seen strange
+          // heap corruption fatal errors that produced mdmp files, but when we load
+          // these mdmp files in WinDBG, "!heap -triage" shows no error.
+          // We can examine the saved_heap_entries[] array in the mdmp file to
+          // diagnose such seemingly spurious errors reported by HeapWalk.
+          saved_heap_entries[saved_heap_entry_index++] = phe;
+          if (saved_heap_entry_index >= SAVE_COUNT) {
+            saved_heap_entry_index = 0;
+          }
         }
       }
       DWORD err = GetLastError();