Index: lib/sanitizer_common/sanitizer_common.h
===================================================================
--- lib/sanitizer_common/sanitizer_common.h
+++ lib/sanitizer_common/sanitizer_common.h
@@ -48,7 +48,7 @@
 static const uptr kErrorMessageBufferSize = 1 << 16;
 
 // Denotes fake PC values that come from JIT/JAVA/etc.
-// For such PC values __tsan_symbolize_external() will be called.
+// For such PC values __tsan_symbolize_external_ex() will be called.
 const u64 kExternalPCBit = 1ULL << 60;
 
 extern const char *SanitizerToolName;  // Can be changed by the tool.
Index: lib/tsan/rtl/tsan_rtl_report.cc
===================================================================
--- lib/tsan/rtl/tsan_rtl_report.cc
+++ lib/tsan/rtl/tsan_rtl_report.cc
@@ -649,8 +649,8 @@
     // callback. Most likely, TraceTopPC will now return a EventTypeFuncExit
     // event. Later we subtract -1 from it (in GetPreviousInstructionPc)
     // and the resulting PC has kExternalPCBit set, so we pass it to
-    // __tsan_symbolize_external. __tsan_symbolize_external is within its rights
-    // to crash since the PC is completely bogus.
+    // __tsan_symbolize_external_ex. __tsan_symbolize_external_ex is within its
+    // rights to crash since the PC is completely bogus.
     // test/tsan/double_race.cc contains a test case for this.
     toppc = 0;
   }
Index: lib/tsan/rtl/tsan_symbolize.cc
===================================================================
--- lib/tsan/rtl/tsan_symbolize.cc
+++ lib/tsan/rtl/tsan_symbolize.cc
@@ -36,6 +36,7 @@
   thr->ignore_interceptors--;
 }
 
+// Legacy API.
 // May be overriden by JIT/JAVA/etc,
 // whatever produces PCs marked with kExternalPCBit.
 SANITIZER_WEAK_DEFAULT_IMPL
@@ -45,9 +46,50 @@
   return false;
 }
 
+// New API: call __tsan_symbolize_external_ex only when it exists.
+// Once old clients are gone, provide dummy implementation.
+extern "C" SANITIZER_INTERFACE_ATTRIBUTE SANITIZER_WEAK_ATTRIBUTE
+void __tsan_symbolize_external_ex(uptr pc,
+                                  void (*add_frame)(void *, const char *,
+                                                    const char *, int, int),
+                                  void *ctx);
+
+struct SymbolizedStackBuilder {
+  SymbolizedStack *head;
+  SymbolizedStack *tail;
+  uptr addr;
+};
+
+static void AddFrame(void *ctx, const char *function_name, const char *file,
+                     int line, int column) {
+  SymbolizedStackBuilder *ssb = (struct SymbolizedStackBuilder *)ctx;
+  if (ssb->tail) {
+    ssb->tail->next = SymbolizedStack::New(ssb->addr);
+    ssb->tail = ssb->tail->next;
+  } else {
+    ssb->head = ssb->tail = SymbolizedStack::New(ssb->addr);
+  }
+  AddressInfo *info = &ssb->tail->info;
+  if (function_name) {
+    info->function = internal_strdup(function_name);
+  }
+  if (file) {
+    info->file = internal_strdup(file);
+  }
+  info->line = line;
+  info->column = column;
+}
+
 SymbolizedStack *SymbolizeCode(uptr addr) {
   // Check if PC comes from non-native land.
   if (addr & kExternalPCBit) {
+    if (__tsan_symbolize_external_ex) {
+      SymbolizedStackBuilder ssb = {nullptr, nullptr, addr};
+      __tsan_symbolize_external_ex(addr, AddFrame, &ssb);
+      return ssb.head ? ssb.head : SymbolizedStack::New(addr);
+    }
+    // Legacy code: remove along with the declaration above
+    // once all clients using this API are gone.
     // Declare static to not consume too much stack space.
     // We symbolize reports in a single thread, so this is fine.
     static char func_buf[1024];
Index: test/tsan/java_symbolization.cc
===================================================================
--- test/tsan/java_symbolization.cc
+++ test/tsan/java_symbolization.cc
@@ -2,18 +2,13 @@
 #include "java.h"
 #include <memory.h>
 
-extern "C" bool __tsan_symbolize_external(jptr pc,
-                                          char *func_buf, jptr func_siz,
-                                          char *file_buf, jptr file_siz,
-                                          int *line, int *col) {
+extern "C" void __tsan_symbolize_external_ex(
+    jptr pc, void (*add_frame)(void *, const char *, const char *, int, int),
+    void *ctx) {
   if (pc == (1234 | kExternalPCBit)) {
-    memcpy(func_buf, "MyFunc", sizeof("MyFunc"));
-    memcpy(file_buf, "MyFile.java", sizeof("MyFile.java"));
-    *line = 1234;
-    *col = 56;
-    return true;
+    add_frame(ctx, "MyInnerFunc", "MyInnerFile.java", 1234, 56);
+    add_frame(ctx, "MyOuterFunc", "MyOuterFile.java", 4321, 65);
   }
-  return false;
 }
 
 void *Thread(void *p) {
@@ -40,5 +35,6 @@
 }
 
 // CHECK: WARNING: ThreadSanitizer: data race
-// CHECK:     #0 MyFunc MyFile.java:1234:56
+// CHECK:     #0 MyInnerFunc MyInnerFile.java:1234:56
+// CHECK:     #1 MyOuterFunc MyOuterFile.java:4321:65
 // CHECK: DONE
Index: test/tsan/java_symbolization_legacy.cc
===================================================================
--- test/tsan/java_symbolization_legacy.cc
+++ test/tsan/java_symbolization_legacy.cc
@@ -0,0 +1,44 @@
+// RUN: %clangxx_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
+#include "java.h"
+#include <memory.h>
+
+extern "C" bool __tsan_symbolize_external(jptr pc,
+                                          char *func_buf, jptr func_siz,
+                                          char *file_buf, jptr file_siz,
+                                          int *line, int *col) {
+  if (pc == (1234 | kExternalPCBit)) {
+    memcpy(func_buf, "MyFunc", sizeof("MyFunc"));
+    memcpy(file_buf, "MyFile.java", sizeof("MyFile.java"));
+    *line = 1234;
+    *col = 56;
+    return true;
+  }
+  return false;
+}
+
+void *Thread(void *p) {
+  barrier_wait(&barrier);
+  __tsan_write1_pc((jptr)p, 1234 | kExternalPCBit);
+  return 0;
+}
+
+int main() {
+  barrier_init(&barrier, 2);
+  int const kHeapSize = 1024 * 1024;
+  jptr jheap = (jptr)malloc(kHeapSize + 8) + 8;
+  __tsan_java_init(jheap, kHeapSize);
+  const int kBlockSize = 16;
+  __tsan_java_alloc(jheap, kBlockSize);
+  pthread_t th;
+  pthread_create(&th, 0, Thread, (void*)jheap);
+  __tsan_write1_pc((jptr)jheap, 1234 | kExternalPCBit);
+  barrier_wait(&barrier);
+  pthread_join(th, 0);
+  __tsan_java_free(jheap, kBlockSize);
+  fprintf(stderr, "DONE\n");
+  return __tsan_java_fini();
+}
+
+// CHECK: WARNING: ThreadSanitizer: data race
+// CHECK:     #0 MyFunc MyFile.java:1234:56
+// CHECK: DONE