1 // Copyright 2014 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 // Tool to log the execution of the process (Chrome). Writes logs containing 6 // time and address of the callback being called for the first time. 7 // 8 // For performance reasons logs are buffered. Every thread has its own buffer 9 // and log file so the contention between threads is minimal. As a side-effect, 10 // functions called might be mentioned in many thread logs. 11 // 12 // A special thread is created in the process to periodically flush logs for all 13 // threads in case the thread had stopped before flushing its logs. 14 // 15 // Also note that the instrumentation code is self-activated. It begins to 16 // record the log data when it is called first, including the run-time startup. 17 // Have it in mind when modifying it, in particular do not use global objects 18 // with constructors as they are called during startup (too late for us). 19 20 #ifndef TOOLS_CYGPROFILE_CYGPROFILE_H_ 21 #define TOOLS_CYGPROFILE_CYGPROFILE_H_ 22 23 #include <vector> 24 25 #include <sys/time.h> 26 #include <sys/types.h> 27 28 #include "base/callback.h" 29 #include "base/containers/hash_tables.h" 30 #include "base/macros.h" 31 #include "base/memory/scoped_ptr.h" 32 #include "base/synchronization/lock.h" 33 #include "build/build_config.h" 34 35 #if !defined(OS_ANDROID) 36 // This is only supported on Android thanks to the fact that on Android 37 // processes (other than the system's zygote) don't fork. 38 // 39 // To make cygprofile truly work (i.e. without any deadlock) on Chrome 40 // platforms that use fork(), cygprofile.cc should be written in a way that 41 // guarantees that: 42 // - No lock is acquired by a foreign thread during fork(). In particular this 43 // means that cygprofile.cc should not perform any heap allocation (since heap 44 // allocators, including TCMalloc generally use locks). 45 // - Only cygprofile.cc uses pthread_atfork() in the whole process. Unlike POSIX 46 // signals, pthread_atfork() doesn't provide a way to install multiple handlers. 47 // Calling pthread_atfork() in cygprofile.cc would override any handler that 48 // could have been installed previously. 49 // 50 // Chrome happens to violate the first requirement at least once by having its 51 // process launcher thread fork. However the child process in that case, when 52 // it's not instrumented with cygprofile, directly calls exec(). This is safe 53 // since the child process doesn't try to release a lock acquired by another 54 // thread in the parent process which would lead to a deadlock. This problem was 55 // actually observed by trying to port the current version of cygprofile.cc to 56 // Linux. 57 #error This is only supported on Android. 58 #endif 59 60 // The following is only exposed for testing. 61 namespace cygprofile { 62 63 class Thread; 64 65 // Single log entry recorded for each function call. 66 struct LogEntry { 67 LogEntry(const void* address); 68 69 const timespec time; 70 const pid_t pid; 71 const pid_t tid; 72 const void* const address; 73 }; 74 75 // Per-thread function calls log. 76 class ThreadLog { 77 public: 78 // Callback invoked for flushing that can be provided for testing. 79 typedef base::Callback<void (std::vector<LogEntry>*)> FlushCallback; 80 81 ThreadLog(); 82 83 // Used for testing. 84 ThreadLog(const FlushCallback& flush_callback); 85 86 ~ThreadLog(); 87 88 // Must only be called from the thread this ThreadLog instance is watching. 89 void AddEntry(void* address); 90 91 // Can be called from any thread. 92 void TakeEntries(std::vector<LogEntry>* output); 93 94 // Flushes the provided vector of entries to a file and clears it. Note that 95 // this can be called from any thread. 96 void Flush(std::vector<LogEntry>* entries) const; 97 98 private: 99 // Default implementation (that can be overridden for testing) of the method 100 // above. 101 void FlushInternal(std::vector<LogEntry>* entries) const; 102 103 // Thread identifier as Linux kernel shows it. LWP (light-weight process) is 104 // a unique ID of the thread in the system, unlike pthread_self() which is the 105 // same for fork()-ed threads. 106 const pid_t tid_; 107 108 // Current thread is inside the instrumentation routine. 109 bool in_use_; 110 111 // Callback used to flush entries. 112 const FlushCallback flush_callback_; 113 114 // Keeps track of all functions that have been logged on this thread so we do 115 // not record duplicates. 116 std::hash_set<void*> called_functions_; 117 118 // A lock that guards |entries_| usage between per-thread instrumentation 119 // routine and timer flush callback. So the contention could happen only 120 // during the flush, every 15 secs. 121 base::Lock lock_; 122 123 std::vector<LogEntry> entries_; 124 125 DISALLOW_COPY_AND_ASSIGN(ThreadLog); 126 }; 127 128 // Manages a list of per-thread logs. 129 class ThreadLogsManager { 130 public: 131 ThreadLogsManager(); 132 133 // Used for testing. The provided callbacks are used for testing to 134 // synchronize the internal thread with the unit test running on the main 135 // thread. 136 ThreadLogsManager(const base::Closure& wait_callback, 137 const base::Closure& notify_callback); 138 139 ~ThreadLogsManager(); 140 141 // Can be called from any thread. 142 void AddLog(scoped_ptr<ThreadLog> new_log); 143 144 private: 145 void StartInternalFlushThread_Locked(); 146 147 // Flush thread's entry point. 148 void FlushAllLogsOnFlushThread(); 149 150 // Used to make the internal thread sleep before each flush iteration. 151 const base::Closure wait_callback_; 152 // Used to trigger a notification when a flush happened on the internal 153 // thread. 154 const base::Closure notify_callback_; 155 156 // Protects the state below. 157 base::Lock lock_; 158 scoped_ptr<Thread> flush_thread_; 159 std::vector<ThreadLog*> logs_; 160 161 DISALLOW_COPY_AND_ASSIGN(ThreadLogsManager); 162 }; 163 164 } // namespace cygprofile 165 166 #endif // TOOLS_CYGPROFILE_CYGPROFILE_H_ 167
