diff --git a/compiler-rt/lib/hwasan/hwasan.cpp b/compiler-rt/lib/hwasan/hwasan.cpp
--- a/compiler-rt/lib/hwasan/hwasan.cpp
+++ b/compiler-rt/lib/hwasan/hwasan.cpp
@@ -86,8 +86,7 @@
     cf.clear_shadow_mmap_threshold = 4096 * (SANITIZER_ANDROID ? 2 : 8);
     // Sigtrap is used in error reporting.
     cf.handle_sigtrap = kHandleSignalExclusive;
-    // FIXME: enable once all false positives have been fixed.
-    cf.detect_leaks = false;
+    cf.detect_leaks = true;
 
 #if SANITIZER_ANDROID
     // Let platform handle other signals. It is better at reporting them then we
diff --git a/compiler-rt/test/hwasan/TestCases/Linux/leak_check_segv.cpp b/compiler-rt/test/hwasan/TestCases/Linux/leak_check_segv.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/hwasan/TestCases/Linux/leak_check_segv.cpp
@@ -0,0 +1,23 @@
+// Test that SIGSEGV during leak checking does not crash the process.
+// RUN: %clangxx_hwasan -O1 %s -o %t && not %run %t 2>&1 | FileCheck %s
+// REQUIRES: leak-detection
+#include <stdlib.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <sanitizer/lsan_interface.h>
+
+char data[10 * 1024 * 1024];
+
+int main() {
+  void *p = malloc(10 * 1024 * 1024);
+  // surprise-surprise!
+  mprotect((void*)(((unsigned long)p + 4095) & ~4095), 16 * 1024, PROT_NONE);
+  mprotect((void*)(((unsigned long)data + 4095) & ~4095), 16 * 1024, PROT_NONE);
+  __lsan_do_leak_check();
+  fprintf(stderr, "DONE\n");
+}
+
+// CHECK: Tracer caught signal 11
+// CHECK: LeakSanitizer has encountered a fatal error
+// CHECK: HINT: For debugging, try setting {{.*}} LSAN_OPTIONS
+// CHECK-NOT: DONE
diff --git a/compiler-rt/test/hwasan/TestCases/Linux/signal_during_stop_the_world.cpp b/compiler-rt/test/hwasan/TestCases/Linux/signal_during_stop_the_world.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/hwasan/TestCases/Linux/signal_during_stop_the_world.cpp
@@ -0,0 +1,60 @@
+// Test StopTheWorld behavior during signal storm.
+// Historically StopTheWorld crashed because did not handle EINTR properly.
+// The test is somewhat convoluted, but that's what caused crashes previously.
+
+// RUN: %clangxx_hwasan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
+#include <time.h>
+#include <pthread.h>
+#include <sanitizer/lsan_interface.h>
+
+static void handler(int signo);
+static void *thr(void *arg);
+
+int main() {
+  struct sigaction act = {};
+  act.sa_handler = handler;
+  sigaction(SIGPROF, &act, 0);
+
+  pid_t pid = fork();
+  if (pid < 0) {
+    fprintf(stderr, "failed to fork\n");
+    exit(1);
+  }
+  if (pid == 0) {
+    // Child constantly sends signals to parent to cause spurious return from
+    // waitpid in StopTheWorld.
+    prctl(PR_SET_PDEATHSIG, SIGTERM, 0, 0, 0);
+    pid_t parent = getppid();
+    for (;;) {
+      // There is no strong reason for these two particular signals,
+      // but at least one of them ought to unblock waitpid.
+      kill(parent, SIGCHLD);
+      kill(parent, SIGPROF);
+    }
+  }
+  usleep(10000);  // Let the child start.
+  __lsan_do_leak_check();
+  // Kill and join the child.
+  kill(pid, SIGTERM);
+  waitpid(pid, 0, 0);
+  sleep(1);  // If the tracer thread still runs, give it time to crash.
+  fprintf(stderr, "DONE\n");
+// CHECK: DONE
+}
+
+static void handler(int signo) {
+}
+
+static void *thr(void *arg) {
+  for (;;)
+    sleep(1);
+  return 0;
+}
diff --git a/compiler-rt/test/hwasan/TestCases/lsan_annotations.cpp b/compiler-rt/test/hwasan/TestCases/lsan_annotations.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/hwasan/TestCases/lsan_annotations.cpp
@@ -0,0 +1,21 @@
+// Check that LSan annotations work fine.
+// RUN: %clangxx_hwasan -O0 %s -o %t && %run %t
+// RUN: %clangxx_hwasan -O3 %s -o %t && %run %t
+
+#include <sanitizer/lsan_interface.h>
+#include <stdlib.h>
+
+int *x, *y;
+
+int main() {
+  x = new int;
+  __lsan_ignore_object(x);
+
+  {
+    __lsan::ScopedDisabler disabler;
+    y = new int;
+  }
+
+  x = y = nullptr;
+  return 0;
+}
\ No newline at end of file
diff --git a/compiler-rt/test/hwasan/TestCases/lsan_crash.cpp b/compiler-rt/test/hwasan/TestCases/lsan_crash.cpp
new file mode 100644
--- /dev/null
+++ b/compiler-rt/test/hwasan/TestCases/lsan_crash.cpp
@@ -0,0 +1,31 @@
+// RUN: %clangxx_hwasan -O2 %s --std=c++14 -o %t && %run %t
+
+#include <atomic>
+#include <memory>
+#include <sanitizer/lsan_interface.h>
+#include <thread>
+#include <vector>
+
+std::atomic<bool> done;
+
+void foo() {
+  std::unique_ptr<char[]> mem;
+
+  while (!done)
+    mem.reset(new char[1000000]);
+}
+
+int main() {
+  std::vector<std::thread> threads;
+  for (int i = 0; i < 10; ++i)
+    threads.emplace_back(foo);
+
+  for (int i = 0; i < 100; ++i)
+    __lsan_do_recoverable_leak_check();
+
+  done = true;
+  for (auto &t : threads)
+    t.join();
+
+  return 0;
+}