Fix thread-safety (annotalysis) annotations

tcmalloc contains some thread-safety annotations; however those
annotations have not been exercised for some time, as they used
macros/attributes only supported by a legacy branch of gcc.

Pull request gperftools#1251 converted those macros to support modern
versions of clang; this CR fixes the annotations that were
enabled. For the most part, this just requires re-enabling
annotations on member functions that take/release locks. For the
tcmalloc fork (pre-fork and post-fork) handlers, we mark the
functions as exempt from this analysis, as it takes a dynamic
number of locks.

src/base/low_level_alloc.cc

@@ -248,7 +248,7 @@ namespace {
       this->arena_->mu.Lock();
     }
     ~ArenaLock() { RAW_CHECK(this->left_, "haven't left Arena region"); }
-    void Leave() /*UNLOCK_FUNCTION()*/ {
+    void Leave() UNLOCK_FUNCTION() {
       this->arena_->mu.Unlock();
 #if 0
       if (this->mask_valid_) {

src/base/spinlock.h

@@ -63,9 +63,7 @@ class LOCKABLE SpinLock {
   }
 
   // Acquire this SpinLock.
-  // TODO(csilvers): uncomment the annotation when we figure out how to
-  //                 support this macro with 0 args (see thread_annotations.h)
-  inline void Lock() /*EXCLUSIVE_LOCK_FUNCTION()*/ {
+  inline void Lock() EXCLUSIVE_LOCK_FUNCTION() {
     if (base::subtle::Acquire_CompareAndSwap(&lockword_, kSpinLockFree,
                                              kSpinLockHeld) != kSpinLockFree) {
       SlowLock();
@@ -84,9 +82,7 @@ class LOCKABLE SpinLock {
   }
 
   // Release this SpinLock, which must be held by the calling thread.
-  // TODO(csilvers): uncomment the annotation when we figure out how to
-  //                 support this macro with 0 args (see thread_annotations.h)
-  inline void Unlock() /*UNLOCK_FUNCTION()*/ {
+  inline void Unlock() UNLOCK_FUNCTION() {
     uint64 prev_value = static_cast<uint64>(
         base::subtle::Release_AtomicExchange(&lockword_, kSpinLockFree));
     if (prev_value != kSpinLockHeld) {
@@ -127,9 +123,7 @@ class SCOPED_LOCKABLE SpinLockHolder {
       : lock_(l) {
     l->Lock();
   }
-  // TODO(csilvers): uncomment the annotation when we figure out how to
-  //                 support this macro with 0 args (see thread_annotations.h)
-  inline ~SpinLockHolder() /*UNLOCK_FUNCTION()*/ { lock_->Unlock(); }
+  inline ~SpinLockHolder() UNLOCK_FUNCTION() { lock_->Unlock(); }
 };
 // Catch bug where variable name is omitted, e.g. SpinLockHolder (&lock);
 #define SpinLockHolder(x) COMPILE_ASSERT(0, spin_lock_decl_missing_var_name)

src/central_freelist.h

@@ -82,11 +82,11 @@ class CentralFreeList {
 
   // Lock/Unlock the internal SpinLock. Used on the pthread_atfork call
   // to set the lock in a consistent state before the fork.
-  void Lock() {
+  void Lock() EXCLUSIVE_LOCK_FUNCTION(lock_) {
     lock_.Lock();
   }
 
-  void Unlock() {
+  void Unlock() UNLOCK_FUNCTION(lock_) {
     lock_.Unlock();
   }
 

src/static_vars.cc

@@ -52,14 +52,14 @@ namespace tcmalloc {
 // sure the central_cache locks remain in a consisten state in the forked
 // version of the thread.
 
-void CentralCacheLockAll()
+void CentralCacheLockAll() NO_THREAD_SAFETY_ANALYSIS
 {
   Static::pageheap_lock()->Lock();
   for (int i = 0; i < Static::num_size_classes(); ++i)
     Static::central_cache()[i].Lock();
 }
 
-void CentralCacheUnlockAll()
+void CentralCacheUnlockAll() NO_THREAD_SAFETY_ANALYSIS
 {
   for (int i = 0; i < Static::num_size_classes(); ++i)
     Static::central_cache()[i].Unlock();