tsan: disable thread safety analysis in more functions

[vitalybuka]

Summary

In preparation for replacing tsan Mutex with sanitizer_common Mutex,
which has thread-safety annotations. Thread safety analysis does not
understand MetaMap::GetAndLock which returns a locked sync object.

Depends on D106490.

compiler-rt/lib/tsan/rtl/tsan_interface_atomic.cpp

 
 #if __TSAN_HAS_INT128 && !SANITIZER_GO
 static a128 NoTsanAtomicLoad(const volatile a128 *a, morder mo) {
   SpinMutexLock lock(&mutex128);
   return *a;
 }
 #endif
 
-template<typename T>
-static T AtomicLoad(ThreadState *thr, uptr pc, const volatile T *a, morder mo) {
+template <typename T>
+static T AtomicLoad(ThreadState *thr, uptr pc, const volatile T *a,
+                    morder mo) NO_THREAD_SAFETY_ANALYSIS {
   CHECK(IsLoadOrder(mo));
   // This fast-path is critical for performance.
   // Assume the access is atomic.
   if (!IsAcquireOrder(mo)) {
     MemoryReadAtomic(thr, pc, (uptr)a, SizeLog<T>());
     return NoTsanAtomicLoad(a, mo);
   }
   // Don't create sync object if it does not exist yet. For example, an atomic

 
 #if __TSAN_HAS_INT128 && !SANITIZER_GO
 static void NoTsanAtomicStore(volatile a128 *a, a128 v, morder mo) {
   SpinMutexLock lock(&mutex128);
   *a = v;
 }
 #endif
 
-template<typename T>
+template <typename T>
 static void AtomicStore(ThreadState *thr, uptr pc, volatile T *a, T v,
-    morder mo) {
+                        morder mo) NO_THREAD_SAFETY_ANALYSIS {
   CHECK(IsStoreOrder(mo));
   MemoryWriteAtomic(thr, pc, (uptr)a, SizeLog<T>());
   // This fast-path is critical for performance.
   // Assume the access is atomic.
   // Strictly saying even relaxed store cuts off release sequence,
   // so must reset the clock.
   if (!IsReleaseOrder(mo)) {
     NoTsanAtomicStore(a, v, mo);
     return;
   }
   __sync_synchronize();
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, (uptr)a, true);
   thr->fast_state.IncrementEpoch();
   // Can't increment epoch w/o writing to the trace as well.
   TraceAddEvent(thr, thr->fast_state, EventTypeMop, 0);
   ReleaseStoreImpl(thr, pc, &s->clock);
   NoTsanAtomicStore(a, v, mo);
   s->mtx.Unlock();
 }
 
-template<typename T, T (*F)(volatile T *v, T op)>
-static T AtomicRMW(ThreadState *thr, uptr pc, volatile T *a, T v, morder mo) {
+template <typename T, T (*F)(volatile T *v, T op)>
+static T AtomicRMW(ThreadState *thr, uptr pc, volatile T *a, T v,
+                   morder mo) NO_THREAD_SAFETY_ANALYSIS {
   MemoryWriteAtomic(thr, pc, (uptr)a, SizeLog<T>());
   SyncVar *s = 0;
   if (mo != mo_relaxed) {
     s = ctx->metamap.GetOrCreateAndLock(thr, pc, (uptr)a, true);
     thr->fast_state.IncrementEpoch();
     // Can't increment epoch w/o writing to the trace as well.
     TraceAddEvent(thr, thr->fast_state, EventTypeMop, 0);
     if (IsAcqRelOrder(mo))

 #endif
 
 template<typename T>
 static T NoTsanAtomicCAS(volatile T *a, T c, T v, morder mo, morder fmo) {
   NoTsanAtomicCAS(a, &c, v, mo, fmo);
   return c;
 }
 
-template<typename T>
-static bool AtomicCAS(ThreadState *thr, uptr pc,
-    volatile T *a, T *c, T v, morder mo, morder fmo) {
+template <typename T>
+static bool AtomicCAS(ThreadState *thr, uptr pc, volatile T *a, T *c, T v,
+                      morder mo, morder fmo) NO_THREAD_SAFETY_ANALYSIS {
   // 31.7.2.18: "The failure argument shall not be memory_order_release
   // nor memory_order_acq_rel". LLVM (2021-05) fallbacks to Monotonic
   // (mo_relaxed) when those are used.
   CHECK(IsLoadOrder(fmo));
 
   MemoryWriteAtomic(thr, pc, (uptr)a, SizeLog<T>());
   SyncVar *s = 0;
   bool write_lock = IsReleaseOrder(mo);

compiler-rt/lib/tsan/rtl/tsan_rtl_mutex.cpp

static void ReportMutexMisuse(ThreadState *thr, uptr pc, ReportType typ,
   rep.AddMutex(mid);
   VarSizeStackTrace trace;
   ObtainCurrentStack(thr, pc, &trace);
   rep.AddStack(trace, true);
   rep.AddLocation(addr, 1);
   OutputReport(thr, rep);
 }
 
-void MutexCreate(ThreadState *thr, uptr pc, uptr addr, u32 flagz) {
+void MutexCreate(ThreadState *thr, uptr pc, uptr addr,
+                 u32 flagz) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexCreate %zx flagz=0x%x\n", thr->tid, addr, flagz);
   if (!(flagz & MutexFlagLinkerInit) && IsAppMem(addr)) {
     CHECK(!thr->is_freeing);
     thr->is_freeing = true;
     MemoryWrite(thr, pc, addr, kSizeLog1);
     thr->is_freeing = false;
   }
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   s->SetFlags(flagz & MutexCreationFlagMask);
   if (!SANITIZER_GO && s->creation_stack_id == 0)
     s->creation_stack_id = CurrentStackId(thr, pc);
   s->mtx.Unlock();
 }
 
-void MutexDestroy(ThreadState *thr, uptr pc, uptr addr, u32 flagz) {
+void MutexDestroy(ThreadState *thr, uptr pc, uptr addr,
+                  u32 flagz) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexDestroy %zx\n", thr->tid, addr);
   SyncVar *s = ctx->metamap.GetIfExistsAndLock(addr, true);
   if (s == 0)
     return;
   if ((flagz & MutexFlagLinkerInit)
       || s->IsFlagSet(MutexFlagLinkerInit)
       || ((flagz & MutexFlagNotStatic) && !s->IsFlagSet(MutexFlagNotStatic))) {
     // Destroy is no-op for linker-initialized mutexes.
if (IsAppMem(addr)) {
     CHECK(!thr->is_freeing);
     thr->is_freeing = true;
     MemoryWrite(thr, pc, addr, kSizeLog1);
     thr->is_freeing = false;
   }
   // s will be destroyed and freed in MetaMap::FreeBlock.
 }
 
-void MutexPreLock(ThreadState *thr, uptr pc, uptr addr, u32 flagz) {
+void MutexPreLock(ThreadState *thr, uptr pc, uptr addr,
+                  u32 flagz) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexPreLock %zx flagz=0x%x\n", thr->tid, addr, flagz);
   if (!(flagz & MutexFlagTryLock) && common_flags()->detect_deadlocks) {
     SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, false);
     s->UpdateFlags(flagz);
     if (s->owner_tid != thr->tid) {
       Callback cb(thr, pc);
       ctx->dd->MutexBeforeLock(&cb, &s->dd, true);
       s->mtx.ReadUnlock();
       ReportDeadlock(thr, pc, ctx->dd->GetReport(&cb));
     } else {
       s->mtx.ReadUnlock();
     }
   }
 }
 
-void MutexPostLock(ThreadState *thr, uptr pc, uptr addr, u32 flagz, int rec) {
+void MutexPostLock(ThreadState *thr, uptr pc, uptr addr, u32 flagz,
+                   int rec) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexPostLock %zx flag=0x%x rec=%d\n",
       thr->tid, addr, flagz, rec);
   if (flagz & MutexFlagRecursiveLock)
     CHECK_GT(rec, 0);
   else
     rec = 1;
   if (IsAppMem(addr))
     MemoryReadAtomic(thr, pc, addr, kSizeLog1);
void MutexPostLock(ThreadState *thr, uptr pc, uptr addr, u32 flagz,
   if (report_double_lock)
     ReportMutexMisuse(thr, pc, ReportTypeMutexDoubleLock, addr, mid);
   if (first && pre_lock && common_flags()->detect_deadlocks) {
     Callback cb(thr, pc);
     ReportDeadlock(thr, pc, ctx->dd->GetReport(&cb));
   }
 }
 
-int MutexUnlock(ThreadState *thr, uptr pc, uptr addr, u32 flagz) {
+int MutexUnlock(ThreadState *thr, uptr pc, uptr addr,
+                u32 flagz) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexUnlock %zx flagz=0x%x\n", thr->tid, addr, flagz);
   if (IsAppMem(addr))
     MemoryReadAtomic(thr, pc, addr, kSizeLog1);
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   thr->fast_state.IncrementEpoch();
   TraceAddEvent(thr, thr->fast_state, EventTypeUnlock, s->GetId());
   int rec = 0;
   bool report_bad_unlock = false;
if (report_bad_unlock)
     ReportMutexMisuse(thr, pc, ReportTypeMutexBadUnlock, addr, mid);
   if (common_flags()->detect_deadlocks && !report_bad_unlock) {
     Callback cb(thr, pc);
     ReportDeadlock(thr, pc, ctx->dd->GetReport(&cb));
   }
   return rec;
 }
 
-void MutexPreReadLock(ThreadState *thr, uptr pc, uptr addr, u32 flagz) {
+void MutexPreReadLock(ThreadState *thr, uptr pc, uptr addr,
+                      u32 flagz) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexPreReadLock %zx flagz=0x%x\n", thr->tid, addr, flagz);
   if (!(flagz & MutexFlagTryLock) && common_flags()->detect_deadlocks) {
     SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, false);
     s->UpdateFlags(flagz);
     Callback cb(thr, pc);
     ctx->dd->MutexBeforeLock(&cb, &s->dd, false);
     s->mtx.ReadUnlock();
     ReportDeadlock(thr, pc, ctx->dd->GetReport(&cb));
   }
 }
 
-void MutexPostReadLock(ThreadState *thr, uptr pc, uptr addr, u32 flagz) {
+void MutexPostReadLock(ThreadState *thr, uptr pc, uptr addr,
+                       u32 flagz) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexPostReadLock %zx flagz=0x%x\n", thr->tid, addr, flagz);
   if (IsAppMem(addr))
     MemoryReadAtomic(thr, pc, addr, kSizeLog1);
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, false);
   s->UpdateFlags(flagz);
   thr->fast_state.IncrementEpoch();
   TraceAddEvent(thr, thr->fast_state, EventTypeRLock, s->GetId());
   bool report_bad_lock = false;
void MutexPostReadLock(ThreadState *thr, uptr pc, uptr addr,
   if (report_bad_lock)
     ReportMutexMisuse(thr, pc, ReportTypeMutexBadReadLock, addr, mid);
   if (pre_lock  && common_flags()->detect_deadlocks) {
     Callback cb(thr, pc);
     ReportDeadlock(thr, pc, ctx->dd->GetReport(&cb));
   }
 }
 
-void MutexReadUnlock(ThreadState *thr, uptr pc, uptr addr) {
+void MutexReadUnlock(ThreadState *thr, uptr pc,
+                     uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexReadUnlock %zx\n", thr->tid, addr);
   if (IsAppMem(addr))
     MemoryReadAtomic(thr, pc, addr, kSizeLog1);
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   thr->fast_state.IncrementEpoch();
   TraceAddEvent(thr, thr->fast_state, EventTypeRUnlock, s->GetId());
   bool report_bad_unlock = false;
   if (s->owner_tid != kInvalidTid) {
void MutexReadUnlock(ThreadState *thr, uptr pc,
   if (report_bad_unlock)
     ReportMutexMisuse(thr, pc, ReportTypeMutexBadReadUnlock, addr, mid);
   if (common_flags()->detect_deadlocks) {
     Callback cb(thr, pc);
     ReportDeadlock(thr, pc, ctx->dd->GetReport(&cb));
   }
 }
 
-void MutexReadOrWriteUnlock(ThreadState *thr, uptr pc, uptr addr) {
+void MutexReadOrWriteUnlock(ThreadState *thr, uptr pc,
+                            uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexReadOrWriteUnlock %zx\n", thr->tid, addr);
   if (IsAppMem(addr))
     MemoryReadAtomic(thr, pc, addr, kSizeLog1);
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   bool write = true;
   bool report_bad_unlock = false;
   if (s->owner_tid == kInvalidTid) {
     // Seems to be read unlock.
void MutexReadOrWriteUnlock(ThreadState *thr, uptr pc,
   if (report_bad_unlock)
     ReportMutexMisuse(thr, pc, ReportTypeMutexBadUnlock, addr, mid);
   if (common_flags()->detect_deadlocks) {
     Callback cb(thr, pc);
     ReportDeadlock(thr, pc, ctx->dd->GetReport(&cb));
   }
 }
 
-void MutexRepair(ThreadState *thr, uptr pc, uptr addr) {
+void MutexRepair(ThreadState *thr, uptr pc,
+                 uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexRepair %zx\n", thr->tid, addr);
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   s->owner_tid = kInvalidTid;
   s->recursion = 0;
   s->mtx.Unlock();
 }
 
-void MutexInvalidAccess(ThreadState *thr, uptr pc, uptr addr) {
+void MutexInvalidAccess(ThreadState *thr, uptr pc,
+                        uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: MutexInvalidAccess %zx\n", thr->tid, addr);
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   u64 mid = s->GetId();
   s->mtx.Unlock();
   ReportMutexMisuse(thr, pc, ReportTypeMutexInvalidAccess, addr, mid);
 }
 
-void Acquire(ThreadState *thr, uptr pc, uptr addr) {
+void Acquire(ThreadState *thr, uptr pc, uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: Acquire %zx\n", thr->tid, addr);
   if (thr->ignore_sync)
     return;
   SyncVar *s = ctx->metamap.GetIfExistsAndLock(addr, false);
   if (!s)
     return;
   AcquireImpl(thr, pc, &s->clock);
   s->mtx.ReadUnlock();
void AcquireGlobal(ThreadState *thr, uptr pc) {
   DPrintf("#%d: AcquireGlobal\n", thr->tid);
   if (thr->ignore_sync)
     return;
   ThreadRegistryLock l(ctx->thread_registry);
   ctx->thread_registry->RunCallbackForEachThreadLocked(
       UpdateClockCallback, thr);
 }
 
-void ReleaseStoreAcquire(ThreadState *thr, uptr pc, uptr addr) {
+void ReleaseStoreAcquire(ThreadState *thr, uptr pc,
+                         uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: ReleaseStoreAcquire %zx\n", thr->tid, addr);
   if (thr->ignore_sync)
     return;
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   thr->fast_state.IncrementEpoch();
   // Can't increment epoch w/o writing to the trace as well.
   TraceAddEvent(thr, thr->fast_state, EventTypeMop, 0);
   ReleaseStoreAcquireImpl(thr, pc, &s->clock);
   s->mtx.Unlock();
 }
 
-void Release(ThreadState *thr, uptr pc, uptr addr) {
+void Release(ThreadState *thr, uptr pc, uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: Release %zx\n", thr->tid, addr);
   if (thr->ignore_sync)
     return;
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   thr->fast_state.IncrementEpoch();
   // Can't increment epoch w/o writing to the trace as well.
   TraceAddEvent(thr, thr->fast_state, EventTypeMop, 0);
   ReleaseImpl(thr, pc, &s->clock);
   s->mtx.Unlock();
 }
 
-void ReleaseStore(ThreadState *thr, uptr pc, uptr addr) {
+void ReleaseStore(ThreadState *thr, uptr pc,
+                  uptr addr) NO_THREAD_SAFETY_ANALYSIS {
   DPrintf("#%d: ReleaseStore %zx\n", thr->tid, addr);
   if (thr->ignore_sync)
     return;
   SyncVar *s = ctx->metamap.GetOrCreateAndLock(thr, pc, addr, true);
   thr->fast_state.IncrementEpoch();
   // Can't increment epoch w/o writing to the trace as well.
   TraceAddEvent(thr, thr->fast_state, EventTypeMop, 0);
   ReleaseStoreImpl(thr, pc, &s->clock);

compiler-rt/lib/tsan/rtl/tsan_rtl_report.cpp

void ScopedReportBase::AddMutex(const SyncVar *s) {
   ReportMutex *rm = new(mem) ReportMutex;
   rep_->mutexes.PushBack(rm);
   rm->id = s->uid;
   rm->addr = s->addr;
   rm->destroyed = false;
   rm->stack = SymbolizeStackId(s->creation_stack_id);
 }
 
-u64 ScopedReportBase::AddMutex(u64 id) {
+u64 ScopedReportBase::AddMutex(u64 id) NO_THREAD_SAFETY_ANALYSIS {
   u64 uid = 0;
   u64 mid = id;
   uptr addr = SyncVar::SplitId(id, &uid);
   SyncVar *s = ctx->metamap.GetIfExistsAndLock(addr, true);
   // Check that the mutex is still alive.
   // Another mutex can be created at the same address,
   // so check uid as well.
   if (s && s->CheckId(uid)) {

compiler-rt/lib/tsan/rtl/tsan_sync.cpp

SyncVar* MetaMap::GetOrCreateAndLock(ThreadState *thr, uptr pc,
                               uptr addr, bool write_lock) {
   return GetAndLock(thr, pc, addr, write_lock, true);
 }
 
 SyncVar* MetaMap::GetIfExistsAndLock(uptr addr, bool write_lock) {
   return GetAndLock(0, 0, addr, write_lock, false);
 }
 
-SyncVar* MetaMap::GetAndLock(ThreadState *thr, uptr pc,
-                             uptr addr, bool write_lock, bool create) {
+SyncVar *MetaMap::GetAndLock(ThreadState *thr, uptr pc, uptr addr,
+                             bool write_lock,
+                             bool create) NO_THREAD_SAFETY_ANALYSIS {
   u32 *meta = MemToMeta(addr);
   u32 idx0 = *meta;
   u32 myidx = 0;
   SyncVar *mys = 0;
   for (;;) {
     u32 idx = idx0;
     for (;;) {
       if (idx == 0)

compiler-rt/lib/tsan/tests/unit/tsan_sync_test.cpp

 //===-- tsan_sync_test.cpp ------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of ThreadSanitizer (TSan), a race detector.
 //
 //===----------------------------------------------------------------------===//
 #include "tsan_sync.h"
 #include "tsan_rtl.h"
 #include "gtest/gtest.h"
 
 namespace __tsan {
 
 TEST(MetaMap, Basic) {
   ThreadState *thr = cur_thread();
   MetaMap *m = &ctx->metamap;
TEST(MetaMap, FreeRange) {
   EXPECT_EQ(mb2->siz, 3 * sizeof(u64));
   m->FreeRange(thr->proc(), (uptr)&block[0], 4 * sizeof(u64));
   mb1 = m->GetBlock((uptr)&block[0]);
   EXPECT_EQ(mb1, (MBlock*)0);
   mb2 = m->GetBlock((uptr)&block[1]);
   EXPECT_EQ(mb2, (MBlock*)0);
 }
 
-TEST(MetaMap, Sync) {
+TEST(MetaMap, Sync) NO_THREAD_SAFETY_ANALYSIS {
+  // EXPECT can call memset/etc. Disable interceptors to prevent
+  // them from detecting that we exit runtime with mutexes held.
+  ScopedIgnoreInterceptors ignore;
   ThreadState *thr = cur_thread();
   MetaMap *m = &ctx->metamap;
   u64 block[4] = {};  // fake malloc block
   m->AllocBlock(thr, 0, (uptr)&block[0], 4 * sizeof(u64));
   SyncVar *s1 = m->GetIfExistsAndLock((uptr)&block[0], true);
   EXPECT_EQ(s1, (SyncVar*)0);
   s1 = m->GetOrCreateAndLock(thr, 0, (uptr)&block[0], true);
   EXPECT_NE(s1, (SyncVar*)0);
   EXPECT_EQ(s1->addr, (uptr)&block[0]);
   s1->mtx.Unlock();
   SyncVar *s2 = m->GetOrCreateAndLock(thr, 0, (uptr)&block[1], false);
   EXPECT_NE(s2, (SyncVar*)0);
   EXPECT_EQ(s2->addr, (uptr)&block[1]);
   s2->mtx.ReadUnlock();
   m->FreeBlock(thr->proc(), (uptr)&block[0]);
   s1 = m->GetIfExistsAndLock((uptr)&block[0], true);
   EXPECT_EQ(s1, (SyncVar*)0);
   s2 = m->GetIfExistsAndLock((uptr)&block[1], true);
   EXPECT_EQ(s2, (SyncVar*)0);
   m->OnProcIdle(thr->proc());
 }
 
-TEST(MetaMap, MoveMemory) {
+TEST(MetaMap, MoveMemory) NO_THREAD_SAFETY_ANALYSIS {
+  ScopedIgnoreInterceptors ignore;
   ThreadState *thr = cur_thread();
   MetaMap *m = &ctx->metamap;
   u64 block1[4] = {};  // fake malloc block
   u64 block2[4] = {};  // fake malloc block
   m->AllocBlock(thr, 0, (uptr)&block1[0], 3 * sizeof(u64));
   m->AllocBlock(thr, 0, (uptr)&block1[3], 1 * sizeof(u64));
   SyncVar *s1 = m->GetOrCreateAndLock(thr, 0, (uptr)&block1[0], true);
   s1->mtx.Unlock();
TEST(MetaMap, MoveMemory) NO_THREAD_SAFETY_ANALYSIS {
   s1->mtx.Unlock();
   s2 = m->GetIfExistsAndLock((uptr)&block2[1], true);
   EXPECT_NE(s2, (SyncVar*)0);
   EXPECT_EQ(s2->addr, (uptr)&block2[1]);
   s2->mtx.Unlock();
   m->FreeRange(thr->proc(), (uptr)&block2[0], 4 * sizeof(u64));
 }
 
-TEST(MetaMap, ResetSync) {
+TEST(MetaMap, ResetSync) NO_THREAD_SAFETY_ANALYSIS {
+  ScopedIgnoreInterceptors ignore;
   ThreadState *thr = cur_thread();
   MetaMap *m = &ctx->metamap;
   u64 block[1] = {};  // fake malloc block
   m->AllocBlock(thr, 0, (uptr)&block[0], 1 * sizeof(u64));
   SyncVar *s = m->GetOrCreateAndLock(thr, 0, (uptr)&block[0], true);
   s->Reset(thr->proc());
   s->mtx.Unlock();
   uptr sz = m->FreeBlock(thr->proc(), (uptr)&block[0]);
   EXPECT_EQ(sz, 1 * sizeof(u64));
 }
 
 }  // namespace __tsan