js/src/threading/Mutex.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "threading/Mutex.h"
   8
   9 using namespace js;
  10
  11 #ifdef DEBUG
  12
  13 MOZ_THREAD_LOCAL(js::Mutex*) js::Mutex::HeldMutexStack;
  14
  15 /* static */
  16 bool js::Mutex::Init() { return HeldMutexStack.init(); }
  17
  18 void js::Mutex::lock() {
  19   preLockChecks();
  20   impl_.lock();
  21   postLockChecks();
  22 }
  23
  24 bool js::Mutex::tryLock() {
  25   preLockChecks();
  26   if (!impl_.tryLock()) {
  27     return false;
  28   }
  29
  30   postLockChecks();
  31   return true;
  32 }
  33
  34 void js::Mutex::preLockChecks() const {
  35   Mutex* prev = HeldMutexStack.get();
  36   if (prev) {
  37     if (id_.order <= prev->id_.order) {
  38       fprintf(stderr,
  39               "Attempt to acquire mutex %s with order %u while holding %s with "
  40               "order %u\n",
  41               id_.name, id_.order, prev->id_.name, prev->id_.order);
  42       MOZ_CRASH("Mutex ordering violation");
  43     }
  44   }
  45 }
  46
  47 void js::Mutex::postLockChecks() {
  48   MOZ_ASSERT(!owningThread_);
  49   owningThread_ = ThreadId::ThisThreadId();
  50
  51   MOZ_ASSERT(prev_ == nullptr);
  52   prev_ = HeldMutexStack.get();
  53   HeldMutexStack.set(this);
  54 }
  55
  56 void js::Mutex::unlock() {
  57   preUnlockChecks();
  58   impl_.unlock();
  59 }
  60
  61 void js::Mutex::preUnlockChecks() {
  62   Mutex* stack = HeldMutexStack.get();
  63   MOZ_ASSERT(stack == this);
  64   HeldMutexStack.set(prev_);
  65   prev_ = nullptr;
  66
  67   MOZ_ASSERT(ThreadId::ThisThreadId() == owningThread_);
  68   owningThread_ = ThreadId();
  69 }
  70
  71 void js::Mutex::assertOwnedByCurrentThread() const {
  72   // This check is only thread-safe if it succeeds.
  73   MOZ_ASSERT(ThreadId::ThisThreadId() == owningThread_);
  74
  75   MOZ_ASSERT(isOwnedByCurrentThread());
  76 }
  77
  78 bool js::Mutex::isOwnedByCurrentThread() const {
  79   // Check whether the mutex is on the thread-local mutex stack.
  80   for (Mutex* mutex = HeldMutexStack.get(); mutex; mutex = mutex->prev_) {
  81     if (mutex == this) {
  82       return true;
  83     }
  84   }
  85
  86   return false;
  87 }
  88
  89 #endif