Bug#35785927 testFK -n TransError -> CMVMI (Line: 1879) 0x00000006 Check cnt_inc > 0

Test used the CmvmiLongSignalMemorySnapshot dump codes to analyse if there
were leaks of LongSignalMemory if a transaction failed. (Lack of cleanup...?)

The amount of such free LongSignalMemory were stored in an array of snapshots,
then later analyzed and require's triggered in Cmvmi::execDUMP_STATE_ORD()
if leaks were belived to be found.

That code had two flaws:

1) When analyzing the snapshots we skipped over every 2'nd snapshot,
thus possibly missing some 'increases' and 'decreases' which were counted.

2) In case the snapshot array could not hold all the snapshots being taken
it wrapped around, writing over the first ones.

Patch fixes:

- All snapshots between 'start' and 'stop' is now analyzed.
- Size of the snapshot array is increased from 32 to 256 element.
  ( Note that 'testFK -n TransError' takes 50 snapshots with default args).
- Removed the wrap around and instead write a warning to the log if
  snapshot array size is exceeded. (-> Code also simplified)

Change-Id: I377e35b72e8d694646ed5a9e949c7c7dea981cd4

Author: Ole John Aske

storage/ndb/src/kernel/blocks/cmvmi/Cmvmi.cpp

@@ -1406,7 +1406,7 @@ cmp_event_buf(const void * ptr0, const void * ptr1)
 }
 
 #if defined VM_TRACE || defined ERROR_INSERT
-static Uint32 f_free_segments[32];
+static Uint32 f_free_segments[256];
 static Uint32 f_free_segment_pos = 0;
 #endif
 
@@ -1564,32 +1564,40 @@ Cmvmi::execDUMP_STATE_ORD(Signal* signal)
   if (arg == DumpStateOrd::CmvmiLongSignalMemorySnapshot)
   {
 #if defined VM_TRACE || defined ERROR_INSERT
-    f_free_segments[f_free_segment_pos] = g_sectionSegmentPool.getNoOfFree();
-    f_free_segment_pos = (f_free_segment_pos + 1) % NDB_ARRAY_SIZE(f_free_segments);
+    if (f_free_segment_pos < NDB_ARRAY_SIZE(f_free_segments))
+    {
+      f_free_segments[f_free_segment_pos++] = g_sectionSegmentPool.getNoOfFree();
+    }
+    else
+    {
+      g_eventLogger->warning("CmvmiLongSignalMemorySnapshot IGNORED"
+                             ", exceeded the max %lu snapshots",
+                             NDB_ARRAY_SIZE(f_free_segments));
+    }
 #endif
   }
 
   if (arg == DumpStateOrd::CmvmiLongSignalMemorySnapshotCheck)
   {
 #if defined VM_TRACE || defined ERROR_INSERT
-    Uint32 start = (f_free_segment_pos + 1)% NDB_ARRAY_SIZE(f_free_segments);
-    Uint32 stop = (f_free_segment_pos - 1) % NDB_ARRAY_SIZE(f_free_segments);
+    Uint32 start = 1;
+    Uint32 stop = f_free_segment_pos;
     Uint32 cnt_dec = 0;
     Uint32 cnt_inc = 0;
     Uint32 cnt_same = 0;
-    for (Uint32 i = start; i != stop; i = (i + 1) % NDB_ARRAY_SIZE(f_free_segments))
+    for (Uint32 i = start; i < stop; i++)
     {
-      Uint32 prev = (i - 1) % NDB_ARRAY_SIZE(f_free_segments);
+      Uint32 prev = (i - 1);
       if (f_free_segments[prev] == f_free_segments[i])
         cnt_same++;
       else if (f_free_segments[prev] > f_free_segments[i])
         cnt_dec++;
-      else if (f_free_segments[prev] < f_free_segments[i])
+      else
         cnt_inc++;
     }
 
     printf("snapshots: ");
-    for (Uint32 i = start; i != stop; i = (i + 1) % NDB_ARRAY_SIZE(f_free_segments))
+    for (Uint32 i = 0; i < stop; i++)
     {
       printf("%u ", f_free_segments[i]);
     }