最近中在看art代码，看到这个函数的时候，想到logcat的events log中有大量的dvm_lock_sameple信息
进程名，主线程？，线程名字，锁等待时间，当前持有者的文件名，行号，上一个持有者文件名，行号，锁等待的百分比
打印此条LOG的时候，上一个锁的持有者已经释放锁，本线程为下一个锁的持有者，即将获取锁上一个持有者的文件名，可能是“-”，表示与持有者是同一个文件。 dvm_lock_sample: [com.banyac.midrive.launcher,1,main,6,SourceFile,234,-,358,1]art/runtime/monitor_android.cc
void Monitor::LogContentionEvent(Thread* self, uint32_t wait_ms, uint32_t sample_percent, const char* owner_filename, uint32_t owner_line_number) { // Emit the event list length, 1 byte. char eventBuffer[174]; char* cp = eventBuffer; *cp++ = 9; // Emit the process name, <= 37 bytes. int fd = open("/proc/self/cmdline", O_RDONLY); char procName[33]; memset(procName, 0, sizeof(procName)); read(fd, procName, sizeof(procName) - 1); close(fd); size_t len = strlen(procName); cp = EventLogWriteString(cp, procName, len); // Emit the sensitive thread ("main thread") status, 5 bytes. cp = EventLogWriteInt(cp, Monitor::IsSensitiveThread()); // Emit self thread name string, <= 37 bytes. std::string thread_name; self->GetThreadName(thread_name); cp = EventLogWriteString(cp, thread_name.c_str(), thread_name.size()); // Emit the wait time, 5 bytes. cp = EventLogWriteInt(cp, wait_ms); // Emit the source code file name, <= 37 bytes. uint32_t pc; mirror::ArtMethod* m = self->GetCurrentMethod(&pc); const char* filename; uint32_t line_number; TranslateLocation(m, pc, &filename, &line_number); cp = EventLogWriteString(cp, filename, strlen(filename)); // Emit the source code line number, 5 bytes. cp = EventLogWriteInt(cp, line_number); // Emit the lock owner source code file name, <= 37 bytes. if (owner_filename == NULL) { owner_filename = ""; } else if (strcmp(filename, owner_filename) == 0) { // Common case, so save on log space. owner_filename = "-"; } cp = EventLogWriteString(cp, owner_filename, strlen(owner_filename)); // Emit the source code line number, 5 bytes. cp = EventLogWriteInt(cp, owner_line_number); // Emit the sample percentage, 5 bytes. cp = EventLogWriteInt(cp, sample_percent); CHECK_LE((size_t)(cp - eventBuffer), sizeof(eventBuffer)); android_btWriteLog(EVENT_LOG_TAG_dvm_lock_sample, EVENT_TYPE_LIST, eventBuffer, (size_t)(cp - eventBuffer)); }