diff --git a/compiler-rt/lib/asan/asan_allocator.cpp b/compiler-rt/lib/asan/asan_allocator.cpp
--- a/compiler-rt/lib/asan/asan_allocator.cpp
+++ b/compiler-rt/lib/asan/asan_allocator.cpp
@@ -476,7 +476,7 @@
       return false;
     if (m->Beg() != addr) return false;
     AsanThread *t = GetCurrentThread();
-    m->SetAllocContext(t ? t->tid() : 0, StackDepotPut(*stack));
+    m->SetAllocContext(t ? t->tid() : kMainTid, StackDepotPut(*stack));
     return true;
   }
 
@@ -570,7 +570,7 @@
     m->SetUsedSize(size);
     m->user_requested_alignment_log = user_requested_alignment_log;
 
-    m->SetAllocContext(t ? t->tid() : 0, StackDepotPut(*stack));
+    m->SetAllocContext(t ? t->tid() : kMainTid, StackDepotPut(*stack));
 
     uptr size_rounded_down_to_granularity =
         RoundDownTo(size, SHADOW_GRANULARITY);
diff --git a/compiler-rt/lib/asan/asan_descriptions.cpp b/compiler-rt/lib/asan/asan_descriptions.cpp
--- a/compiler-rt/lib/asan/asan_descriptions.cpp
+++ b/compiler-rt/lib/asan/asan_descriptions.cpp
@@ -44,7 +44,7 @@
   CHECK(context);
   asanThreadRegistry().CheckLocked();
   // No need to announce the main thread.
-  if (context->tid == 0 || context->announced) {
+  if (context->tid == kMainTid || context->announced) {
     return;
   }
   context->announced = true;
diff --git a/compiler-rt/lib/asan/asan_thread.h b/compiler-rt/lib/asan/asan_thread.h
--- a/compiler-rt/lib/asan/asan_thread.h
+++ b/compiler-rt/lib/asan/asan_thread.h
@@ -28,7 +28,6 @@
 
 namespace __asan {
 
-const u32 kInvalidTid = 0xffffff;  // Must fit into 24 bits.
 const u32 kMaxNumberOfThreads = (1 << 22);  // 4M
 
 class AsanThread;
diff --git a/compiler-rt/lib/asan/asan_thread.cpp b/compiler-rt/lib/asan/asan_thread.cpp
--- a/compiler-rt/lib/asan/asan_thread.cpp
+++ b/compiler-rt/lib/asan/asan_thread.cpp
@@ -228,7 +228,7 @@
 }
 
 void AsanThread::Init(const InitOptions *options) {
-  DCHECK_NE(tid(), ThreadRegistry::kUnknownTid);
+  DCHECK_NE(tid(), kInvalidTid);
   next_stack_top_ = next_stack_bottom_ = 0;
   atomic_store(&stack_switching_, false, memory_order_release);
   CHECK_EQ(this->stack_size(), 0U);
@@ -291,7 +291,7 @@
 
 AsanThread *CreateMainThread() {
   AsanThread *main_thread = AsanThread::Create(
-      /* start_routine */ nullptr, /* arg */ nullptr, /* parent_tid */ 0,
+      /* start_routine */ nullptr, /* arg */ nullptr, /* parent_tid */ kMainTid,
       /* stack */ nullptr, /* detached */ true);
   SetCurrentThread(main_thread);
   main_thread->ThreadStart(internal_getpid());
@@ -305,8 +305,8 @@
   DCHECK_EQ(options, nullptr);
   uptr tls_size = 0;
   uptr stack_size = 0;
-  GetThreadStackAndTls(tid() == 0, &stack_bottom_, &stack_size, &tls_begin_,
-                       &tls_size);
+  GetThreadStackAndTls(tid() == kMainTid, &stack_bottom_, &stack_size,
+                       &tls_begin_, &tls_size);
   stack_top_ = RoundDownTo(stack_bottom_ + stack_size, SHADOW_GRANULARITY);
   tls_end_ = tls_begin_ + tls_size;
   dtls_ = DTLS_Get();
@@ -431,7 +431,7 @@
       // address. We are not entirely sure that we have correct main thread
       // limits, so only do this magic on Android, and only if the found thread
       // is the main thread.
-      AsanThreadContext *tctx = GetThreadContextByTidLocked(0);
+      AsanThreadContext *tctx = GetThreadContextByTidLocked(kMainTid);
       if (tctx && ThreadStackContainsAddress(tctx, &context)) {
         SetCurrentThread(tctx->thread);
         return tctx->thread;
@@ -468,7 +468,7 @@
 void EnsureMainThreadIDIsCorrect() {
   AsanThreadContext *context =
       reinterpret_cast<AsanThreadContext *>(AsanTSDGet());
-  if (context && (context->tid == 0))
+  if (context && (context->tid == kMainTid))
     context->os_id = GetTid();
 }
 
diff --git a/compiler-rt/lib/lsan/lsan_common.h b/compiler-rt/lib/lsan/lsan_common.h
--- a/compiler-rt/lib/lsan/lsan_common.h
+++ b/compiler-rt/lib/lsan/lsan_common.h
@@ -66,8 +66,6 @@
   kIgnored = 3
 };
 
-const u32 kInvalidTid = (u32) -1;
-
 struct Flags {
 #define LSAN_FLAG(Type, Name, DefaultValue, Description) Type Name;
 #include "lsan_flags.inc"
diff --git a/compiler-rt/lib/lsan/lsan_interceptors.cpp b/compiler-rt/lib/lsan/lsan_interceptors.cpp
--- a/compiler-rt/lib/lsan/lsan_interceptors.cpp
+++ b/compiler-rt/lib/lsan/lsan_interceptors.cpp
@@ -460,7 +460,7 @@
   if (res == 0) {
     int tid = ThreadCreate(GetCurrentThread(), *(uptr *)th,
                            IsStateDetached(detached));
-    CHECK_NE(tid, 0);
+    CHECK_NE(tid, kMainTid);
     atomic_store(&p.tid, tid, memory_order_release);
     while (atomic_load(&p.tid, memory_order_acquire) != 0)
       internal_sched_yield();
diff --git a/compiler-rt/lib/lsan/lsan_posix.cpp b/compiler-rt/lib/lsan/lsan_posix.cpp
--- a/compiler-rt/lib/lsan/lsan_posix.cpp
+++ b/compiler-rt/lib/lsan/lsan_posix.cpp
@@ -48,7 +48,7 @@
   OnStartedArgs args;
   uptr stack_size = 0;
   uptr tls_size = 0;
-  GetThreadStackAndTls(tid == 0, &args.stack_begin, &stack_size,
+  GetThreadStackAndTls(tid == kMainTid, &args.stack_begin, &stack_size,
                        &args.tls_begin, &tls_size);
   args.stack_end = args.stack_begin + stack_size;
   args.tls_end = args.tls_begin + tls_size;
@@ -75,8 +75,8 @@
 }
 
 void InitializeMainThread() {
-  u32 tid = ThreadCreate(0, 0, true);
-  CHECK_EQ(tid, 0);
+  u32 tid = ThreadCreate(kMainTid, 0, true);
+  CHECK_EQ(tid, kMainTid);
   ThreadStart(tid, GetTid());
 }
 
diff --git a/compiler-rt/lib/lsan/lsan_thread.cpp b/compiler-rt/lib/lsan/lsan_thread.cpp
--- a/compiler-rt/lib/lsan/lsan_thread.cpp
+++ b/compiler-rt/lib/lsan/lsan_thread.cpp
@@ -94,7 +94,7 @@
 }
 
 void EnsureMainThreadIDIsCorrect() {
-  if (GetCurrentThread() == 0)
+  if (GetCurrentThread() == kMainTid)
     CurrentThreadContext()->os_id = GetTid();
 }
 
diff --git a/compiler-rt/lib/memprof/memprof_descriptions.cpp b/compiler-rt/lib/memprof/memprof_descriptions.cpp
--- a/compiler-rt/lib/memprof/memprof_descriptions.cpp
+++ b/compiler-rt/lib/memprof/memprof_descriptions.cpp
@@ -44,7 +44,7 @@
   CHECK(context);
   memprofThreadRegistry().CheckLocked();
   // No need to announce the main thread.
-  if (context->tid == 0 || context->announced) {
+  if (context->tid == kMainTid || context->announced) {
     return;
   }
   context->announced = true;
diff --git a/compiler-rt/lib/memprof/memprof_thread.h b/compiler-rt/lib/memprof/memprof_thread.h
--- a/compiler-rt/lib/memprof/memprof_thread.h
+++ b/compiler-rt/lib/memprof/memprof_thread.h
@@ -27,7 +27,6 @@
 
 namespace __memprof {
 
-const u32 kInvalidTid = 0xffffff;          // Must fit into 24 bits.
 const u32 kMaxNumberOfThreads = (1 << 22); // 4M
 
 class MemprofThread;
diff --git a/compiler-rt/lib/memprof/memprof_thread.cpp b/compiler-rt/lib/memprof/memprof_thread.cpp
--- a/compiler-rt/lib/memprof/memprof_thread.cpp
+++ b/compiler-rt/lib/memprof/memprof_thread.cpp
@@ -156,7 +156,7 @@
 
 MemprofThread *CreateMainThread() {
   MemprofThread *main_thread = MemprofThread::Create(
-      /* start_routine */ nullptr, /* arg */ nullptr, /* parent_tid */ 0,
+      /* start_routine */ nullptr, /* arg */ nullptr, /* parent_tid */ kMainTid,
       /* stack */ nullptr, /* detached */ true);
   SetCurrentThread(main_thread);
   main_thread->ThreadStart(internal_getpid(),
@@ -171,8 +171,8 @@
   DCHECK_EQ(options, nullptr);
   uptr tls_size = 0;
   uptr stack_size = 0;
-  GetThreadStackAndTls(tid() == 0, &stack_bottom_, &stack_size, &tls_begin_,
-                       &tls_size);
+  GetThreadStackAndTls(tid() == kMainTid, &stack_bottom_, &stack_size,
+                       &tls_begin_, &tls_size);
   stack_top_ = stack_bottom_ + stack_size;
   tls_end_ = tls_begin_ + tls_size;
   dtls_ = DTLS_Get();
@@ -214,7 +214,7 @@
 void EnsureMainThreadIDIsCorrect() {
   MemprofThreadContext *context =
       reinterpret_cast<MemprofThreadContext *>(TSDGet());
-  if (context && (context->tid == 0))
+  if (context && (context->tid == kMainTid))
     context->os_id = GetTid();
 }
 } // namespace __memprof
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h b/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h
--- a/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_internal_defs.h
@@ -409,6 +409,9 @@
     (void)enable_fp;                      \
   } while (0)
 
+constexpr u32 kInvalidTid = -1;
+constexpr u32 kMainTid = 0;
+
 }  // namespace __sanitizer
 
 namespace __asan {
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.h b/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.h
--- a/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.h
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.h
@@ -87,8 +87,6 @@
 
 class ThreadRegistry {
  public:
-  static const u32 kUnknownTid;
-
   ThreadRegistry(ThreadContextFactory factory, u32 max_threads,
                  u32 thread_quarantine_size, u32 max_reuse = 0);
   void GetNumberOfThreads(uptr *total = nullptr, uptr *running = nullptr,
@@ -113,7 +111,7 @@
   void RunCallbackForEachThreadLocked(ThreadCallback cb, void *arg);
 
   typedef bool (*FindThreadCallback)(ThreadContextBase *tctx, void *arg);
-  // Finds a thread using the provided callback. Returns kUnknownTid if no
+  // Finds a thread using the provided callback. Returns kInvalidTid if no
   // thread is found.
   u32 FindThread(FindThreadCallback cb, void *arg);
   // Should be guarded by ThreadRegistryLock. Return 0 if no thread
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.cpp b/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.cpp
--- a/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.cpp
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_thread_registry.cpp
@@ -85,7 +85,7 @@
   unique_id = _unique_id;
   detached = _detached;
   // Parent tid makes no sense for the main thread.
-  if (tid != 0)
+  if (tid != kMainTid)
     parent_tid = _parent_tid;
   OnCreated(arg);
 }
@@ -99,8 +99,6 @@
 
 // ThreadRegistry implementation.
 
-const u32 ThreadRegistry::kUnknownTid = ~0U;
-
 ThreadRegistry::ThreadRegistry(ThreadContextFactory factory, u32 max_threads,
                                u32 thread_quarantine_size, u32 max_reuse)
     : context_factory_(factory),
@@ -135,7 +133,7 @@
 u32 ThreadRegistry::CreateThread(uptr user_id, bool detached, u32 parent_tid,
                                  void *arg) {
   BlockingMutexLock l(&mtx_);
-  u32 tid = kUnknownTid;
+  u32 tid = kInvalidTid;
   ThreadContextBase *tctx = QuarantinePop();
   if (tctx) {
     tid = tctx->tid;
@@ -155,7 +153,7 @@
     Die();
   }
   CHECK_NE(tctx, 0);
-  CHECK_NE(tid, kUnknownTid);
+  CHECK_NE(tid, kInvalidTid);
   CHECK_LT(tid, max_threads_);
   CHECK_EQ(tctx->status, ThreadStatusInvalid);
   alive_threads_++;
@@ -186,7 +184,7 @@
     if (tctx != 0 && cb(tctx, arg))
       return tctx->tid;
   }
-  return kUnknownTid;
+  return kInvalidTid;
 }
 
 ThreadContextBase *
diff --git a/compiler-rt/lib/sanitizer_common/tests/sanitizer_thread_registry_test.cpp b/compiler-rt/lib/sanitizer_common/tests/sanitizer_thread_registry_test.cpp
--- a/compiler-rt/lib/sanitizer_common/tests/sanitizer_thread_registry_test.cpp
+++ b/compiler-rt/lib/sanitizer_common/tests/sanitizer_thread_registry_test.cpp
@@ -98,12 +98,10 @@
   registry->SetThreadName(6, "six");
   registry->SetThreadName(7, "seven");
   EXPECT_EQ(7U, registry->FindThread(HasName, (void*)"seven"));
-  EXPECT_EQ(ThreadRegistry::kUnknownTid,
-            registry->FindThread(HasName, (void*)"none"));
+  EXPECT_EQ(kInvalidTid, registry->FindThread(HasName, (void *)"none"));
   EXPECT_EQ(0U, registry->FindThread(HasUid, (void*)get_uid(0)));
   EXPECT_EQ(10U, registry->FindThread(HasUid, (void*)get_uid(10)));
-  EXPECT_EQ(ThreadRegistry::kUnknownTid,
-            registry->FindThread(HasUid, (void*)0x1234));
+  EXPECT_EQ(kInvalidTid, registry->FindThread(HasUid, (void *)0x1234));
   // Detach and finish and join remaining threads.
   for (u32 i = 6; i <= 10; i++) {
     registry->DetachThread(i, 0);
diff --git a/compiler-rt/lib/tsan/rtl/tsan_clock.h b/compiler-rt/lib/tsan/rtl/tsan_clock.h
--- a/compiler-rt/lib/tsan/rtl/tsan_clock.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_clock.h
@@ -63,6 +63,8 @@
   friend class ThreadClock;
   friend class Iter;
   static const uptr kDirtyTids = 2;
+  // Full kInvalidTid won't fit into Dirty::tid.
+  static const u64 kInvalidTid = (1ull << (64 - kClkBits)) - 1;
 
   struct Dirty {
     u64 epoch  : kClkBits;
@@ -146,6 +148,7 @@
 
  private:
   static const uptr kDirtyTids = SyncClock::kDirtyTids;
+  static const u64 kInvalidTid = SyncClock::kInvalidTid;
   // Index of the thread associated with he clock ("current thread").
   const unsigned tid_;
   const unsigned reused_;  // tid_ reuse count.
diff --git a/compiler-rt/lib/tsan/rtl/tsan_defs.h b/compiler-rt/lib/tsan/rtl/tsan_defs.h
--- a/compiler-rt/lib/tsan/rtl/tsan_defs.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_defs.h
@@ -98,8 +98,6 @@
 const bool kCollectHistory = true;
 #endif
 
-const u16 kInvalidTid = kMaxTid + 1;
-
 // The following "build consistency" machinery ensures that all source files
 // are built in the same configuration. Inconsistent builds lead to
 // hard to debug crashes.
diff --git a/compiler-rt/lib/tsan/rtl/tsan_report.cpp b/compiler-rt/lib/tsan/rtl/tsan_report.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_report.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_report.cpp
@@ -69,7 +69,7 @@
 
 const int kThreadBufSize = 32;
 const char *thread_name(char *buf, int tid) {
-  if (tid == 0)
+  if (tid == kMainTid)
     return "main thread";
   internal_snprintf(buf, kThreadBufSize, "thread T%d", tid);
   return buf;
@@ -250,7 +250,7 @@
 
 static void PrintThread(const ReportThread *rt) {
   Decorator d;
-  if (rt->id == 0)  // Little sense in describing the main thread.
+  if (rt->id == kMainTid)  // Little sense in describing the main thread.
     return;
   Printf("%s", d.ThreadDescription());
   Printf("  Thread T%d", rt->id);
@@ -394,7 +394,7 @@
 
 #else  // #if !SANITIZER_GO
 
-const int kMainThreadId = 1;
+const u32 kMainGoroutineId = 1;
 
 void PrintStack(const ReportStack *ent) {
   if (ent == 0 || ent->frames == 0) {
@@ -415,7 +415,7 @@
   Printf("%s at %p by ",
       (first ? (mop->write ? "Write" : "Read")
              : (mop->write ? "Previous write" : "Previous read")), mop->addr);
-  if (mop->tid == kMainThreadId)
+  if (mop->tid == kMainGoroutineId)
     Printf("main goroutine:\n");
   else
     Printf("goroutine %d:\n", mop->tid);
@@ -428,7 +428,7 @@
     Printf("\n");
     Printf("Heap block of size %zu at %p allocated by ",
         loc->heap_chunk_size, loc->heap_chunk_start);
-    if (loc->tid == kMainThreadId)
+    if (loc->tid == kMainGoroutineId)
       Printf("main goroutine:\n");
     else
       Printf("goroutine %d:\n", loc->tid);
@@ -448,7 +448,7 @@
 }
 
 static void PrintThread(const ReportThread *rt) {
-  if (rt->id == kMainThreadId)
+  if (rt->id == kMainGoroutineId)
     return;
   Printf("\n");
   Printf("Goroutine %d (%s) created at:\n",
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
@@ -406,7 +406,7 @@
 #if TSAN_COLLECT_STATS
   u64 stat[StatCnt];
 #endif
-  const int tid;
+  const u32 tid;
   const int unique_id;
   bool in_symbolizer;
   bool in_ignored_lib;
@@ -447,9 +447,8 @@
 
   const ReportDesc *current_report;
 
-  explicit ThreadState(Context *ctx, int tid, int unique_id, u64 epoch,
-                       unsigned reuse_count,
-                       uptr stk_addr, uptr stk_size,
+  explicit ThreadState(Context *ctx, u32 tid, int unique_id, u64 epoch,
+                       unsigned reuse_count, uptr stk_addr, uptr stk_size,
                        uptr tls_addr, uptr tls_size);
 };
 
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
@@ -129,27 +129,30 @@
 }
 
 // The objects are allocated in TLS, so one may rely on zero-initialization.
-ThreadState::ThreadState(Context *ctx, int tid, int unique_id, u64 epoch,
-                         unsigned reuse_count,
-                         uptr stk_addr, uptr stk_size,
+ThreadState::ThreadState(Context *ctx, u32 tid, int unique_id, u64 epoch,
+                         unsigned reuse_count, uptr stk_addr, uptr stk_size,
                          uptr tls_addr, uptr tls_size)
-  : fast_state(tid, epoch)
-  // Do not touch these, rely on zero initialization,
-  // they may be accessed before the ctor.
-  // , ignore_reads_and_writes()
-  // , ignore_interceptors()
-  , clock(tid, reuse_count)
+    : fast_state(tid, epoch)
+      // Do not touch these, rely on zero initialization,
+      // they may be accessed before the ctor.
+      // , ignore_reads_and_writes()
+      // , ignore_interceptors()
+      ,
+      clock(tid, reuse_count)
 #if !SANITIZER_GO
-  , jmp_bufs()
+      ,
+      jmp_bufs()
 #endif
-  , tid(tid)
-  , unique_id(unique_id)
-  , stk_addr(stk_addr)
-  , stk_size(stk_size)
-  , tls_addr(tls_addr)
-  , tls_size(tls_size)
+      ,
+      tid(tid),
+      unique_id(unique_id),
+      stk_addr(stk_addr),
+      stk_size(stk_size),
+      tls_addr(tls_addr),
+      tls_size(tls_size)
 #if !SANITIZER_GO
-  , last_sleep_clock(tid)
+      ,
+      last_sleep_clock(tid)
 #endif
 {
 }
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl_mutex.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl_mutex.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl_mutex.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl_mutex.cpp
@@ -98,9 +98,8 @@
     ctx->dd->MutexInit(&cb, &s->dd);
   }
   bool unlock_locked = false;
-  if (flags()->report_destroy_locked
-      && s->owner_tid != SyncVar::kInvalidTid
-      && !s->IsFlagSet(MutexFlagBroken)) {
+  if (flags()->report_destroy_locked && s->owner_tid != kInvalidTid &&
+      !s->IsFlagSet(MutexFlagBroken)) {
     s->SetFlags(MutexFlagBroken);
     unlock_locked = true;
   }
@@ -171,7 +170,7 @@
   thr->fast_state.IncrementEpoch();
   TraceAddEvent(thr, thr->fast_state, EventTypeLock, s->GetId());
   bool report_double_lock = false;
-  if (s->owner_tid == SyncVar::kInvalidTid) {
+  if (s->owner_tid == kInvalidTid) {
     CHECK_EQ(s->recursion, 0);
     s->owner_tid = thr->tid;
     s->last_lock = thr->fast_state.raw();
@@ -231,7 +230,7 @@
     s->recursion -= rec;
     if (s->recursion == 0) {
       StatInc(thr, StatMutexUnlock);
-      s->owner_tid = SyncVar::kInvalidTid;
+      s->owner_tid = kInvalidTid;
       ReleaseStoreImpl(thr, pc, &s->clock);
     } else {
       StatInc(thr, StatMutexRecUnlock);
@@ -277,7 +276,7 @@
   thr->fast_state.IncrementEpoch();
   TraceAddEvent(thr, thr->fast_state, EventTypeRLock, s->GetId());
   bool report_bad_lock = false;
-  if (s->owner_tid != SyncVar::kInvalidTid) {
+  if (s->owner_tid != kInvalidTid) {
     if (flags()->report_mutex_bugs && !s->IsFlagSet(MutexFlagBroken)) {
       s->SetFlags(MutexFlagBroken);
       report_bad_lock = true;
@@ -316,7 +315,7 @@
   thr->fast_state.IncrementEpoch();
   TraceAddEvent(thr, thr->fast_state, EventTypeRUnlock, s->GetId());
   bool report_bad_unlock = false;
-  if (s->owner_tid != SyncVar::kInvalidTid) {
+  if (s->owner_tid != kInvalidTid) {
     if (flags()->report_mutex_bugs && !s->IsFlagSet(MutexFlagBroken)) {
       s->SetFlags(MutexFlagBroken);
       report_bad_unlock = true;
@@ -346,7 +345,7 @@
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   bool write = true;
   bool report_bad_unlock = false;
-  if (s->owner_tid == SyncVar::kInvalidTid) {
+  if (s->owner_tid == kInvalidTid) {
     // Seems to be read unlock.
     write = false;
     StatInc(thr, StatMutexReadUnlock);
@@ -361,7 +360,7 @@
     s->recursion--;
     if (s->recursion == 0) {
       StatInc(thr, StatMutexUnlock);
-      s->owner_tid = SyncVar::kInvalidTid;
+      s->owner_tid = kInvalidTid;
       ReleaseStoreImpl(thr, pc, &s->clock);
     } else {
       StatInc(thr, StatMutexRecUnlock);
@@ -389,7 +388,7 @@
 void MutexRepair(ThreadState *thr, uptr pc, uptr addr) {
   DPrintf("#%d: MutexRepair %zx\n", thr->tid, addr);
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
-  s->owner_tid = SyncVar::kInvalidTid;
+  s->owner_tid = kInvalidTid;
   s->recursion = 0;
   s->mtx.Unlock();
 }
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
@@ -51,7 +51,7 @@
 
 void ThreadContext::OnCreated(void *arg) {
   thr = 0;
-  if (tid == 0)
+  if (tid == kMainTid)
     return;
   OnCreatedArgs *args = static_cast<OnCreatedArgs *>(arg);
   if (!args->thr)  // GCD workers don't have a parent thread.
@@ -179,7 +179,7 @@
 
 #if !SANITIZER_GO
 static void ReportIgnoresEnabled(ThreadContext *tctx, IgnoreSet *set) {
-  if (tctx->tid == 0) {
+  if (tctx->tid == kMainTid) {
     Printf("ThreadSanitizer: main thread finished with ignores enabled\n");
   } else {
     Printf("ThreadSanitizer: thread T%d %s finished with ignores enabled,"
@@ -250,9 +250,10 @@
   uptr tls_size = 0;
 #if !SANITIZER_GO
   if (thread_type != ThreadType::Fiber)
-    GetThreadStackAndTls(tid == 0, &stk_addr, &stk_size, &tls_addr, &tls_size);
+    GetThreadStackAndTls(tid == kMainTid, &stk_addr, &stk_size, &tls_addr,
+                         &tls_size);
 
-  if (tid) {
+  if (tid != kMainTid) {
     if (stk_addr && stk_size)
       MemoryRangeImitateWrite(thr, /*pc=*/ 1, stk_addr, stk_size);
 
@@ -313,7 +314,7 @@
 int ThreadConsumeTid(ThreadState *thr, uptr pc, uptr uid) {
   ConsumeThreadContext findCtx = {uid, nullptr};
   ctx->thread_registry->FindThread(ConsumeThreadByUid, &findCtx);
-  int tid = findCtx.tctx ? findCtx.tctx->tid : ThreadRegistry::kUnknownTid;
+  int tid = findCtx.tctx ? findCtx.tctx->tid : kInvalidTid;
   DPrintf("#%d: ThreadTid uid=%zu tid=%d\n", thr->tid, uid, tid);
   return tid;
 }
diff --git a/compiler-rt/lib/tsan/rtl/tsan_sync.h b/compiler-rt/lib/tsan/rtl/tsan_sync.h
--- a/compiler-rt/lib/tsan/rtl/tsan_sync.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_sync.h
@@ -50,13 +50,11 @@
 struct SyncVar {
   SyncVar();
 
-  static const int kInvalidTid = -1;
-
   uptr addr;  // overwritten by DenseSlabAlloc freelist
   Mutex mtx;
   u64 uid;  // Globally unique id.
   u32 creation_stack_id;
-  int owner_tid;  // Set only by exclusive owners.
+  u32 owner_tid;  // Set only by exclusive owners.
   u64 last_lock;
   int recursion;
   atomic_uint32_t flags;