diff --git a/compiler-rt/lib/tsan/rtl/tsan_mman.cpp b/compiler-rt/lib/tsan/rtl/tsan_mman.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_mman.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_mman.cpp
@@ -220,7 +220,7 @@
 void OnUserAlloc(ThreadState *thr, uptr pc, uptr p, uptr sz, bool write) {
   DPrintf("#%d: alloc(%zu) = 0x%zx\n", thr->tid, sz, p);
   ctx->metamap.AllocBlock(thr, pc, p, sz);
-  if (write && thr->ignore_reads_and_writes == 0)
+  if (write && thr->ignore_reads_and_writes == 0 && thr->is_inited)
     MemoryRangeImitateWrite(thr, pc, (uptr)p, sz);
   else
     MemoryResetRange(thr, pc, (uptr)p, sz);
@@ -230,7 +230,7 @@
   CHECK_NE(p, (void*)0);
   uptr sz = ctx->metamap.FreeBlock(thr->proc(), p);
   DPrintf("#%d: free(0x%zx, %zu)\n", thr->tid, p, sz);
-  if (write && thr->ignore_reads_and_writes == 0)
+  if (write && thr->ignore_reads_and_writes == 0 && thr->is_inited)
     MemoryRangeFreed(thr, pc, (uptr)p, sz);
 }
 
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.h b/compiler-rt/lib/tsan/rtl/tsan_rtl.h
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.h
@@ -159,12 +159,8 @@
 #if !SANITIZER_GO
   IgnoreSet mop_ignore_set;
   IgnoreSet sync_ignore_set;
-  // C/C++ uses fixed size shadow stack.
-  uptr shadow_stack[kShadowStackSize];
-#else
-  // Go uses malloc-allocated shadow stack with dynamic size.
-  uptr *shadow_stack;
 #endif
+  uptr *shadow_stack;
   uptr *shadow_stack_end;
   uptr *shadow_stack_pos;
   RawShadow *racy_shadow_addr;
@@ -616,6 +612,9 @@
                                         EventType typ, u64 addr) {
   if (!kCollectHistory)
     return;
+  // TraceSwitch accesses shadow_stack, but it's called infrequently,
+  // so we check it here proactively.
+  DCHECK(thr->shadow_stack);
   DCHECK_GE((int)typ, 0);
   DCHECK_LE((int)typ, 7);
   DCHECK_EQ(GetLsb(addr, kEventPCBits), addr);
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
@@ -148,15 +148,19 @@
 {
   CHECK_EQ(reinterpret_cast<uptr>(this) % SANITIZER_CACHE_LINE_SIZE, 0);
 #if !SANITIZER_GO
-  shadow_stack_pos = shadow_stack;
-  shadow_stack_end = shadow_stack + kShadowStackSize;
+  // C/C++ uses fixed size shadow stack.
+  const int kInitStackSize = kShadowStackSize;
+  shadow_stack = static_cast<uptr *>(
+      MmapNoReserveOrDie(kInitStackSize * sizeof(uptr), "shadow stack"));
+  SetShadowRegionHugePageMode(reinterpret_cast<uptr>(shadow_stack),
+                              kInitStackSize * sizeof(uptr));
 #else
-  // Setup dynamic shadow stack.
+  // Go uses malloc-allocated shadow stack with dynamic size.
   const int kInitStackSize = 8;
-  shadow_stack = (uptr *)Alloc(kInitStackSize * sizeof(uptr));
+  shadow_stack = static_cast<uptr *>(Alloc(kInitStackSize * sizeof(uptr)));
+#endif
   shadow_stack_pos = shadow_stack;
   shadow_stack_end = shadow_stack + kInitStackSize;
-#endif
 }
 
 #if !SANITIZER_GO
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl_thread.cpp
@@ -227,15 +227,11 @@
   if (thr->tls_addr && thr->tls_size)
     DontNeedShadowFor(thr->tls_addr, thr->tls_size);
   thr->is_dead = true;
+  thr->is_inited = false;
   ctx->thread_registry.FinishThread(thr->tid);
 }
 
 void ThreadContext::OnFinished() {
-#if SANITIZER_GO
-  Free(thr->shadow_stack);
-  thr->shadow_stack_pos = nullptr;
-  thr->shadow_stack_end = nullptr;
-#endif
   if (!detached) {
     thr->fast_state.IncrementEpoch();
     // Can't increment epoch w/o writing to the trace as well.
@@ -244,6 +240,15 @@
   }
   epoch1 = thr->fast_state.epoch();
 
+#if !SANITIZER_GO
+  UnmapOrDie(thr->shadow_stack, kShadowStackSize * sizeof(uptr));
+#else
+  Free(thr->shadow_stack);
+#endif
+  thr->shadow_stack = nullptr;
+  thr->shadow_stack_pos = nullptr;
+  thr->shadow_stack_end = nullptr;
+
   if (common_flags()->detect_deadlocks)
     ctx->dd->DestroyLogicalThread(thr->dd_lt);
   thr->clock.ResetCached(&thr->proc()->clock_cache);