| // Copyright 2014 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| // |
| // Tool to log the execution of the process (Chrome). Writes logs containing |
| // time and address of the callback being called for the first time. |
| // |
| // For performance reasons logs are buffered. Every thread has its own buffer |
| // and log file so the contention between threads is minimal. As a side-effect, |
| // functions called might be mentioned in many thread logs. |
| // |
| // A special thread is created in the process to periodically flush logs for all |
| // threads in case the thread had stopped before flushing its logs. |
| // |
| // Also note that the instrumentation code is self-activated. It begins to |
| // record the log data when it is called first, including the run-time startup. |
| // Have it in mind when modifying it, in particular do not use global objects |
| // with constructors as they are called during startup (too late for us). |
| |
| #ifndef TOOLS_CYGPROFILE_CYGPROFILE_H_ |
| #define TOOLS_CYGPROFILE_CYGPROFILE_H_ |
| |
| #include <sys/time.h> |
| #include <sys/types.h> |
| |
| #include <memory> |
| #include <vector> |
| |
| #include "base/callback.h" |
| #include "base/containers/hash_tables.h" |
| #include "base/macros.h" |
| #include "base/synchronization/lock.h" |
| #include "build/build_config.h" |
| |
| #if !defined(OS_ANDROID) |
| // This is only supported on Android thanks to the fact that on Android |
| // processes (other than the system's zygote) don't fork. |
| // |
| // To make cygprofile truly work (i.e. without any deadlock) on Chrome |
| // platforms that use fork(), cygprofile.cc should be written in a way that |
| // guarantees that: |
| // - No lock is acquired by a foreign thread during fork(). In particular this |
| // means that cygprofile.cc should not perform any heap allocation (since heap |
| // allocators, including TCMalloc generally use locks). |
| // - Only cygprofile.cc uses pthread_atfork() in the whole process. Unlike POSIX |
| // signals, pthread_atfork() doesn't provide a way to install multiple handlers. |
| // Calling pthread_atfork() in cygprofile.cc would override any handler that |
| // could have been installed previously. |
| // |
| // Chrome happens to violate the first requirement at least once by having its |
| // process launcher thread fork. However the child process in that case, when |
| // it's not instrumented with cygprofile, directly calls exec(). This is safe |
| // since the child process doesn't try to release a lock acquired by another |
| // thread in the parent process which would lead to a deadlock. This problem was |
| // actually observed by trying to port the current version of cygprofile.cc to |
| // Linux. |
| #error This is only supported on Android. |
| #endif |
| |
| // The following is only exposed for testing. |
| namespace cygprofile { |
| |
| class Thread; |
| |
| // Single log entry recorded for each function call. |
| struct LogEntry { |
| LogEntry(const void* address, pid_t pid, pid_t tid); |
| |
| const timespec time; |
| const pid_t pid; |
| const pid_t tid; |
| const void* const address; |
| }; |
| |
| // Per-thread function calls log. |
| class ThreadLog { |
| public: |
| // Callback invoked for flushing that can be provided for testing. |
| typedef base::Callback<void (std::vector<LogEntry>*)> FlushCallback; |
| |
| ThreadLog(); |
| |
| // Used for testing. |
| ThreadLog(const FlushCallback& flush_callback); |
| |
| ~ThreadLog(); |
| |
| // Must only be called from the thread this ThreadLog instance is watching. |
| void AddEntry(void* address); |
| |
| // Can be called from any thread. |
| void TakeEntries(std::vector<LogEntry>* output); |
| |
| // Flushes the provided vector of entries to a file and clears it. Note that |
| // this can be called from any thread. |
| void Flush(std::vector<LogEntry>* entries) const; |
| |
| private: |
| // Default implementation (that can be overridden for testing) of the method |
| // above. |
| void FlushInternal(std::vector<LogEntry>* entries) const; |
| |
| // Process ID, as returned by getpid(). |
| const pid_t pid_; |
| |
| // Thread identifier as Linux kernel shows it. LWP (light-weight process) is |
| // a unique ID of the thread in the system, unlike pthread_self() which is the |
| // same for fork()-ed threads. |
| const pid_t tid_; |
| |
| // Current thread is inside the instrumentation routine. |
| bool in_use_; |
| |
| // Callback used to flush entries. |
| const FlushCallback flush_callback_; |
| |
| // Keeps track of all functions that have been logged on this thread so we do |
| // not record duplicates. |
| base::hash_set<void*> called_functions_; |
| |
| // A lock that guards |entries_| usage between per-thread instrumentation |
| // routine and timer flush callback. So the contention could happen only |
| // during the flush, every 15 secs. |
| base::Lock lock_; |
| |
| std::vector<LogEntry> entries_; |
| |
| DISALLOW_COPY_AND_ASSIGN(ThreadLog); |
| }; |
| |
| // Manages a list of per-thread logs. |
| class ThreadLogsManager { |
| public: |
| ThreadLogsManager(); |
| |
| // Used for testing. The provided callbacks are used for testing to |
| // synchronize the internal thread with the unit test running on the main |
| // thread. |
| ThreadLogsManager(const base::Closure& wait_callback, |
| const base::Closure& notify_callback); |
| |
| ~ThreadLogsManager(); |
| |
| // Can be called from any thread. |
| void AddLog(std::unique_ptr<ThreadLog> new_log); |
| |
| private: |
| void StartInternalFlushThread_Locked(); |
| |
| // Flush thread's entry point. |
| void FlushAllLogsOnFlushThread(); |
| |
| // Used to make the internal thread sleep before each flush iteration. |
| const base::Closure wait_callback_; |
| // Used to trigger a notification when a flush happened on the internal |
| // thread. |
| const base::Closure notify_callback_; |
| |
| // Protects the state below. |
| base::Lock lock_; |
| std::unique_ptr<Thread> flush_thread_; |
| std::vector<std::unique_ptr<ThreadLog>> logs_; |
| |
| DISALLOW_COPY_AND_ASSIGN(ThreadLogsManager); |
| }; |
| |
| } // namespace cygprofile |
| |
| #endif // TOOLS_CYGPROFILE_CYGPROFILE_H_ |