Index: lib/lsan/lsan_common.cc
===================================================================
--- lib/lsan/lsan_common.cc
+++ lib/lsan/lsan_common.cc
@@ -449,6 +449,8 @@
     Report(
         "HINT: For debugging, try setting environment variable "
         "LSAN_OPTIONS=verbosity=1:log_threads=1\n");
+    Report(
+        "HINT: LeakSanitizer does not work under ptrace (strace, gdb, etc)\n");
     Die();
   }
   param.leak_report.ApplySuppressions();
Index: lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
===================================================================
--- lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
+++ lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
@@ -190,6 +190,7 @@
 bool ThreadSuspender::SuspendAllThreads() {
   ThreadLister thread_lister(pid_);
   bool added_threads;
+  bool first_iteration = true;
   do {
     // Run through the directory entries once.
     added_threads = false;
@@ -199,12 +200,13 @@
         added_threads = true;
       tid = thread_lister.GetNextTID();
     }
-    if (thread_lister.error()) {
+    if (thread_lister.error() || (first_iteration && !added_threads)) {
       // Detach threads and fail.
       ResumeAllThreads();
       return false;
     }
     thread_lister.Reset();
+    first_iteration = false;
   } while (added_threads);
   return true;
 }
Index: test/lsan/TestCases/strace_test.cc
===================================================================
--- /dev/null
+++ test/lsan/TestCases/strace_test.cc
@@ -0,0 +1,14 @@
+// Test that lsan reports a proper error when running under strace.
+// RUN: %clangxx_lsan %s -o %t
+// RUN: not strace -o /dev/null %run %t 2>&1 | FileCheck %s
+
+#include <stdio.h>
+#include <stdlib.h>
+
+static volatile void *sink;
+
+int main() {
+  sink = malloc(42);
+}
+// CHECK: LeakSanitizer has encountered a fatal error
+// CHECK: HINT: LeakSanitizer does not work under ptrace (strace, gdb, etc)