1 /* 2 * Copyright (C) 2011 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #include "scoped_flock.h" 18 19 #include <sys/file.h> 20 #include <sys/stat.h> 21 22 #include "base/logging.h" 23 #include "base/stringprintf.h" 24 #include "base/unix_file/fd_file.h" 25 26 namespace art { 27 28 bool ScopedFlock::Init(const char* filename, std::string* error_msg) { 29 while (true) { 30 file_.reset(OS::OpenFileWithFlags(filename, O_CREAT | O_RDWR)); 31 if (file_.get() == NULL) { 32 *error_msg = StringPrintf("Failed to open file '%s': %s", filename, strerror(errno)); 33 return false; 34 } 35 int flock_result = TEMP_FAILURE_RETRY(flock(file_->Fd(), LOCK_EX)); 36 if (flock_result != 0) { 37 *error_msg = StringPrintf("Failed to lock file '%s': %s", filename, strerror(errno)); 38 return false; 39 } 40 struct stat fstat_stat; 41 int fstat_result = TEMP_FAILURE_RETRY(fstat(file_->Fd(), &fstat_stat)); 42 if (fstat_result != 0) { 43 *error_msg = StringPrintf("Failed to fstat file '%s': %s", filename, strerror(errno)); 44 return false; 45 } 46 struct stat stat_stat; 47 int stat_result = TEMP_FAILURE_RETRY(stat(filename, &stat_stat)); 48 if (stat_result != 0) { 49 PLOG(WARNING) << "Failed to stat, will retry: " << filename; 50 // ENOENT can happen if someone racing with us unlinks the file we created so just retry. 51 continue; 52 } 53 if (fstat_stat.st_dev != stat_stat.st_dev || fstat_stat.st_ino != stat_stat.st_ino) { 54 LOG(WARNING) << "File changed while locking, will retry: " << filename; 55 continue; 56 } 57 return true; 58 } 59 } 60 61 bool ScopedFlock::Init(File* file, std::string* error_msg) { 62 file_.reset(new File(dup(file->Fd()))); 63 if (file_->Fd() == -1) { 64 file_.reset(); 65 *error_msg = StringPrintf("Failed to duplicate open file '%s': %s", 66 file->GetPath().c_str(), strerror(errno)); 67 return false; 68 } 69 if (0 != TEMP_FAILURE_RETRY(flock(file_->Fd(), LOCK_EX))) { 70 file_.reset(); 71 *error_msg = StringPrintf("Failed to lock file '%s': %s", file->GetPath().c_str(), strerror(errno)); 72 return false; 73 } 74 return true; 75 } 76 77 File* ScopedFlock::GetFile() { 78 CHECK(file_.get() != NULL); 79 return file_.get(); 80 } 81 82 bool ScopedFlock::HasFile() { 83 return file_.get() != nullptr; 84 } 85 86 ScopedFlock::ScopedFlock() { } 87 88 ScopedFlock::~ScopedFlock() { 89 if (file_.get() != NULL) { 90 int flock_result = TEMP_FAILURE_RETRY(flock(file_->Fd(), LOCK_UN)); 91 CHECK_EQ(0, flock_result); 92 } 93 } 94 95 } // namespace art 96