Index: openmp/tools/archer/README.md
===================================================================
--- openmp/tools/archer/README.md
+++ openmp/tools/archer/README.md
@@ -104,7 +104,11 @@
 <tr>
 <td class="org-left">flush&#95;shadow</td>
 <td class="org-right">0</td>
-<td class="org-left">Flush shadow memory at the end of an outer OpenMP parallel region. Our experiments show that this can reduce memory overhead by ~30% and runtime overhead by ~10%. This flag is useful for large OpenMP applications that typically require large amounts of memory, causing out-of-memory exceptions when checked by Archer.</td>
+<td class="org-left">Flush shadow memory at the end of an outer OpenMP
+parallel region. Our experiments show that this can reduce memory overhead
+by ~30% and runtime overhead by ~10%. This flag is useful for large OpenMP
+applications that typically require large amounts of memory, causing
+out-of-memory exceptions when checked by Archer.</td>
 </tr>
 </tbody>
 
@@ -118,6 +122,17 @@
 
 <tbody>
 <tr>
+<td class="org-left">ignore&#95;serial</td>
+<td class="org-right">0</td>
+<td class="org-left">Turn off tracking and analysis of memory accesses in
+the sequential part of an OpenMP program. (Only effective when OpenMP
+runtime is initialized. In doubt, insert omp_get_max_threads() as first
+statement in main!)</td>
+</tr>
+</tbody>
+
+<tbody>
+<tr>
 <td class="org-left">verbose</td>
 <td class="org-right">0</td>
 <td class="org-left">Print startup information.</td>
Index: openmp/tools/archer/ompt-tsan.cpp
===================================================================
--- openmp/tools/archer/ompt-tsan.cpp
+++ openmp/tools/archer/ompt-tsan.cpp
@@ -43,18 +43,14 @@
 class ArcherFlags {
 public:
 #if (LLVM_VERSION) >= 40
-  int flush_shadow;
+  int flush_shadow{0};
 #endif
-  int print_max_rss;
-  int verbose;
-  int enabled;
+  int print_max_rss{0};
+  int verbose{0};
+  int enabled{1};
+  int ignore_serial{0};
 
-  ArcherFlags(const char *env)
-      :
-#if (LLVM_VERSION) >= 40
-        flush_shadow(0),
-#endif
-        print_max_rss(0), verbose(0), enabled(1) {
+  ArcherFlags(const char *env) {
     if (env) {
       std::vector<std::string> tokens;
       std::string token;
@@ -75,6 +71,8 @@
           continue;
         if (sscanf(it->c_str(), "enable=%d", &enabled))
           continue;
+        if (sscanf(it->c_str(), "ignore_serial=%d", &ignore_serial))
+          continue;
         std::cerr << "Illegal values for ARCHER_OPTIONS variable: " << token
                   << std::endl;
       }
@@ -505,12 +503,16 @@
   parallel_data->ptr = Data;
 
   TsanHappensBefore(Data->GetParallelPtr());
+  if (archer_flags->ignore_serial && ToTaskData(parent_task_data)->isInitial())
+    TsanIgnoreWritesEnd();
 }
 
 static void ompt_tsan_parallel_end(ompt_data_t *parallel_data,
                                    ompt_data_t *task_data,
                                    int flag,
                                    const void *codeptr_ra) {
+  if (archer_flags->ignore_serial && ToTaskData(task_data)->isInitial())
+    TsanIgnoreWritesBegin();
   ParallelData *Data = ToParallelData(parallel_data);
   TsanHappensAfter(Data->GetBarrierPtr(0));
   TsanHappensAfter(Data->GetBarrierPtr(1));
@@ -909,10 +911,14 @@
         stderr,
         "Warning: please export TSAN_OPTIONS='ignore_noninstrumented_modules=1' "
         "to avoid false positive reports from the OpenMP runtime!\n");
+  if (archer_flags->ignore_serial)
+    TsanIgnoreWritesBegin();
   return 1; // success
 }
 
 static void ompt_tsan_finalize(ompt_data_t *tool_data) {
+  if (archer_flags->ignore_serial)
+    TsanIgnoreWritesEnd();
   if (archer_flags->print_max_rss) {
     struct rusage end;
     getrusage(RUSAGE_SELF, &end);