1 // Copyright 2016 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 "mojo/public/cpp/bindings/sync_call_restrictions.h" 6 7 #if ENABLE_SYNC_CALL_RESTRICTIONS 8 9 #include "base/debug/leak_annotations.h" 10 #include "base/lazy_instance.h" 11 #include "base/logging.h" 12 #include "base/threading/thread_local.h" 13 #include "mojo/public/c/system/core.h" 14 15 namespace mojo { 16 17 namespace { 18 19 class SyncCallSettings { 20 public: 21 static SyncCallSettings* current(); 22 allowed() const23 bool allowed() const { 24 return scoped_allow_count_ > 0 || system_defined_value_; 25 } 26 IncreaseScopedAllowCount()27 void IncreaseScopedAllowCount() { scoped_allow_count_++; } DecreaseScopedAllowCount()28 void DecreaseScopedAllowCount() { 29 DCHECK_LT(0u, scoped_allow_count_); 30 scoped_allow_count_--; 31 } 32 33 private: 34 SyncCallSettings(); 35 ~SyncCallSettings(); 36 37 bool system_defined_value_ = true; 38 size_t scoped_allow_count_ = 0; 39 }; 40 41 base::LazyInstance<base::ThreadLocalPointer<SyncCallSettings>>::DestructorAtExit 42 g_sync_call_settings = LAZY_INSTANCE_INITIALIZER; 43 44 // static current()45SyncCallSettings* SyncCallSettings::current() { 46 SyncCallSettings* result = g_sync_call_settings.Pointer()->Get(); 47 if (!result) { 48 result = new SyncCallSettings(); 49 ANNOTATE_LEAKING_OBJECT_PTR(result); 50 DCHECK_EQ(result, g_sync_call_settings.Pointer()->Get()); 51 } 52 return result; 53 } 54 SyncCallSettings()55SyncCallSettings::SyncCallSettings() { 56 MojoResult result = MojoGetProperty(MOJO_PROPERTY_TYPE_SYNC_CALL_ALLOWED, 57 &system_defined_value_); 58 DCHECK_EQ(MOJO_RESULT_OK, result); 59 60 DCHECK(!g_sync_call_settings.Pointer()->Get()); 61 g_sync_call_settings.Pointer()->Set(this); 62 } 63 ~SyncCallSettings()64SyncCallSettings::~SyncCallSettings() { 65 g_sync_call_settings.Pointer()->Set(nullptr); 66 } 67 68 } // namespace 69 70 // static AssertSyncCallAllowed()71void SyncCallRestrictions::AssertSyncCallAllowed() { 72 if (!SyncCallSettings::current()->allowed()) { 73 LOG(FATAL) << "Mojo sync calls are not allowed in this process because " 74 << "they can lead to jank and deadlock. If you must make an " 75 << "exception, please see " 76 << "SyncCallRestrictions::ScopedAllowSyncCall and consult " 77 << "mojo/OWNERS."; 78 } 79 } 80 81 // static IncreaseScopedAllowCount()82void SyncCallRestrictions::IncreaseScopedAllowCount() { 83 SyncCallSettings::current()->IncreaseScopedAllowCount(); 84 } 85 86 // static DecreaseScopedAllowCount()87void SyncCallRestrictions::DecreaseScopedAllowCount() { 88 SyncCallSettings::current()->DecreaseScopedAllowCount(); 89 } 90 91 } // namespace mojo 92 93 #endif // ENABLE_SYNC_CALL_RESTRICTIONS 94