Index: lib/asan/asan_posix.cc
===================================================================
--- lib/asan/asan_posix.cc
+++ lib/asan/asan_posix.cc
@@ -46,11 +46,14 @@
   // We also check si_code to filter out SEGV caused by something else other
   // then hitting the guard page or unmapped memory, like, for example,
   // unaligned memory access.
+  CHECK_EQ(false, in_sigsegv_handler);
+  in_sigsegv_handler = true;
   if (addr + 128 > sp && addr < sp + 0xFFFF &&
       (code == si_SEGV_MAPERR || code == si_SEGV_ACCERR))
     ReportStackOverflow(pc, sp, bp, context, addr);
   else
     ReportSIGSEGV("SEGV", pc, sp, bp, context, addr);
+  in_sigsegv_handler = false;
 }
 
 // ---------------------- TSD ---------------- {{{1
Index: lib/sanitizer_common/sanitizer_internal_defs.h
===================================================================
--- lib/sanitizer_common/sanitizer_internal_defs.h
+++ lib/sanitizer_common/sanitizer_internal_defs.h
@@ -210,6 +210,8 @@
 SANITIZER_INTERFACE_ATTRIBUTE
 void NORETURN CheckFailed(const char *file, int line, const char *cond,
                           u64 v1, u64 v2);
+
+extern bool in_sigsegv_handler;
 }  // namespace __sanitizer
 
 // Check macro
Index: lib/sanitizer_common/sanitizer_stacktrace.h
===================================================================
--- lib/sanitizer_common/sanitizer_stacktrace.h
+++ lib/sanitizer_common/sanitizer_stacktrace.h
@@ -15,6 +15,10 @@
 
 #include "sanitizer_internal_defs.h"
 
+#if SANITIZER_FREEBSD
+#include <osreldate.h>  // for __FreeBSD_version
+#endif
+
 namespace __sanitizer {
 
 static const uptr kStackTraceMax = 256;
@@ -29,6 +33,13 @@
 # define SANITIZER_CAN_FAST_UNWIND 1
 #endif
 
+// Fast unwind is the only option on Mac.
+#if SANITIZER_MAC
+# define SANITIZER_CAN_SLOW_UNWIND 0
+#else
+# define SANITIZER_CAN_SLOW_UNWIND 1
+#endif
+
 struct StackTrace {
   const uptr *trace;
   uptr size;
@@ -40,13 +51,14 @@
   void Print() const;
 
   static bool WillUseFastUnwind(bool request_fast_unwind) {
-    // Check if fast unwind is available. Fast unwind is the only option on Mac.
-    // It is also the only option on FreeBSD as the slow unwinding that
-    // leverages _Unwind_Backtrace() yields the call stack of the signal's
-    // handler and not of the code that raised the signal (as it does on Linux).
     if (!SANITIZER_CAN_FAST_UNWIND)
       return false;
-    else if (SANITIZER_MAC != 0 || SANITIZER_FREEBSD != 0)
+    else if (!SANITIZER_CAN_SLOW_UNWIND)
+      return true;
+    else if (SANITIZER_FREEBSD && in_sigsegv_handler)
+      // On FreeBSD the slow unwinding that leverages _Unwind_Backtrace()
+      // yields the call stack of the signal's handler and not of the code
+      // that raised the signal (as it does on Linux).
       return true;
     return request_fast_unwind;
   }
Index: lib/sanitizer_common/sanitizer_stacktrace.cc
===================================================================
--- lib/sanitizer_common/sanitizer_stacktrace.cc
+++ lib/sanitizer_common/sanitizer_stacktrace.cc
@@ -17,6 +17,8 @@
 
 namespace __sanitizer {
 
+bool in_sigsegv_handler = false;
+
 uptr StackTrace::GetPreviousInstructionPc(uptr pc) {
 #if defined(__arm__)
   // Cancel Thumb bit.