v1

Author: zhengyu123

ddprof-lib/src/main/cpp/threadFilter.cpp

@@ -99,7 +99,8 @@ int ThreadFilter::mapThreadId(int thread_id) {
 
 // Get bitmap that contains the thread id, create one if it does not exist
 u64* ThreadFilter::getBitmapFor(int thread_id) {
-  int index = static_cast<u32>(thread_id) / BITMAP_CAPACITY;
+  int index = thread_id / BITMAP_CAPACITY;
+  assert(index >= 0 && index < (int)_max_bitmaps);
   u64* b = _bitmap[index];
   if (b == NULL) {
     b = (u64 *)OS::safeAlloc(BITMAP_SIZE);

ddprof-lib/src/main/java/com/datadoghq/profiler/ActiveBitmaps.java

@@ -0,0 +1,79 @@
+package com.datadoghq.profiler;
+
+import sun.misc.Unsafe;
+import java.lang.reflect.Field;
+
+
+class ActiveBitmaps {
+  private static final Unsafe UNSAFE;
+  static {
+        Unsafe unsafe = null;
+        try {
+          Field f = Unsafe.class.getDeclaredField("theUnsafe");
+          f.setAccessible(true);
+          unsafe = (Unsafe) f.get(null);
+        } catch (Exception ignore) { }
+        UNSAFE = unsafe;
+  }
+
+  private static long activeCountAddr = 0;
+
+  private static final ThreadLocal<Long> Address = new ThreadLocal<Long>() {
+    @Override protected Long initialValue() {
+        return -1L;
+    }
+  };
+
+  public static void initialize() {
+    activeCountAddr = getActiveCountAddr0(); 
+  }
+
+  static long getBitmask(int tid) {
+    int tmp = (tid >> 8) & 0xff ;
+    int bits = 0;
+    for (int index = 0; index < 7 ; index++) {
+      if ((tmp & 0x01) == 0x01) {
+        bits |= 0x01;
+      }
+      tmp >>= 1;
+      bits <<= 1; 
+    }
+    return 1L << (bits & 0x3f);
+  }
+
+  static void setActive(int tid, boolean active) {
+     long addr = Address.get();
+     if (addr == -1) {
+       addr = bitmapAddressFor0(tid);
+       Address.set(addr);
+     }
+     long bitmask = getBitmask(tid);
+     long value = UNSAFE.getLong(addr);
+     long newVal; 
+     if (active) {
+       newVal = value | bitmask;  
+     } else {
+       newVal = value & ~bitmask;
+     }
+     while (!UNSAFE.compareAndSwapLong(null, addr, value, newVal)) {
+       value = UNSAFE.getLong(addr);
+       newVal = active ? (value | bitmask) : (value & ~bitmask);
+     }
+     int delta = active ? 1 : -1;
+     assert activeCountAddr != 0;
+     UNSAFE.getAndAddInt(null, activeCountAddr, delta);
+     if (isActive0(tid) != active) {
+       throw new RuntimeException("SetActive failed");
+     }
+
+     assert isActive0(tid) == active;
+  }
+
+  // For verification 
+  private static native boolean isActive0(int tid);
+
+  // Setup bitmap and active count locations
+  private static native long bitmapAddressFor0(int tid);
+  private static native long getActiveCountAddr0();
+}
+