ppapi/shared_impl/proxy_lock.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ppapi/shared_impl/proxy_lock.h"
   6
   7 #include "base/lazy_instance.h"
   8 #include "base/synchronization/lock.h"
   9 #include "base/threading/thread_local.h"
  10 #include "ppapi/shared_impl/ppapi_globals.h"
  11
  12 namespace ppapi {
  13
  14 base::LazyInstance<base::Lock>::Leaky g_proxy_lock = LAZY_INSTANCE_INITIALIZER;
  15
  16 bool g_disable_locking = false;
  17 base::LazyInstance<base::ThreadLocalBoolean>::Leaky
  18     g_disable_locking_for_thread = LAZY_INSTANCE_INITIALIZER;
  19
  20 // Simple single-thread deadlock detector for the proxy lock.
  21 // |true| when the current thread has the lock.
  22 base::LazyInstance<base::ThreadLocalBoolean>::Leaky g_proxy_locked_on_thread =
  23     LAZY_INSTANCE_INITIALIZER;
  24
  25 // static
  26 base::Lock* ProxyLock::Get() {
  27   if (g_disable_locking || g_disable_locking_for_thread.Get().Get())
  28     return NULL;
  29   return &g_proxy_lock.Get();
  30 }
  31
  32 // Functions below should only access the lock via Get to ensure that they don't
  33 // try to use the lock on the host side of the proxy, where locking is
  34 // unnecessary and wrong (because we haven't coded the host side to account for
  35 // locking).
  36
  37 // static
  38 void ProxyLock::Acquire() {
  39   base::Lock* lock = Get();
  40   if (lock) {
  41     // This thread does not already hold the lock.
  42     const bool deadlock = g_proxy_locked_on_thread.Get().Get();
  43     CHECK(!deadlock);
  44
  45     lock->Acquire();
  46     g_proxy_locked_on_thread.Get().Set(true);
  47   }
  48 }
  49
  50 // static
  51 void ProxyLock::Release() {
  52   base::Lock* lock = Get();
  53   if (lock) {
  54     // This thread currently holds the lock.
  55     const bool locked = g_proxy_locked_on_thread.Get().Get();
  56     CHECK(locked);
  57
  58     g_proxy_locked_on_thread.Get().Set(false);
  59     lock->Release();
  60   }
  61 }
  62
  63 // static
  64 void ProxyLock::AssertAcquired() {
  65   base::Lock* lock = Get();
  66   if (lock) {
  67     // This thread currently holds the lock.
  68     const bool locked = g_proxy_locked_on_thread.Get().Get();
  69     CHECK(locked);
  70
  71     lock->AssertAcquired();
  72   }
  73 }
  74
  75 // static
  76 void ProxyLock::DisableLocking() {
  77   // Note, we don't DCHECK that this flag isn't already set, because multiple
  78   // unit tests may run in succession and all set it.
  79   g_disable_locking = true;
  80 }
  81
  82 ProxyLock::LockingDisablerForTest::LockingDisablerForTest() {
  83   // Note, we don't DCHECK that this flag isn't already set, because multiple
  84   // unit tests may run in succession and all set it.
  85   g_disable_locking_for_thread.Get().Set(true);
  86 }
  87
  88 ProxyLock::LockingDisablerForTest::~LockingDisablerForTest() {
  89   g_disable_locking_for_thread.Get().Set(false);
  90 }
  91
  92 void CallWhileUnlocked(const base::Closure& closure) {
  93   ProxyAutoUnlock lock;
  94   closure.Run();
  95 }
  96
  97 }  // namespace ppapi