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 if (file_.get() != nullptr) { 31 UNUSED(file_->FlushCloseOrErase()); // Ignore result. 32 } 33 file_.reset(OS::OpenFileWithFlags(filename, O_CREAT | O_RDWR)); 34 if (file_.get() == nullptr) { 35 *error_msg = StringPrintf("Failed to open file '%s': %s", filename, strerror(errno)); 36 return false; 37 } 38 int flock_result = TEMP_FAILURE_RETRY(flock(file_->Fd(), LOCK_EX)); 39 if (flock_result != 0) { 40 *error_msg = StringPrintf("Failed to lock file '%s': %s", filename, strerror(errno)); 41 return false; 42 } 43 struct stat fstat_stat; 44 int fstat_result = TEMP_FAILURE_RETRY(fstat(file_->Fd(), &fstat_stat)); 45 if (fstat_result != 0) { 46 *error_msg = StringPrintf("Failed to fstat file '%s': %s", filename, strerror(errno)); 47 return false; 48 } 49 struct stat stat_stat; 50 int stat_result = TEMP_FAILURE_RETRY(stat(filename, &stat_stat)); 51 if (stat_result != 0) { 52 PLOG(WARNING) << "Failed to stat, will retry: " << filename; 53 // ENOENT can happen if someone racing with us unlinks the file we created so just retry. 54 continue; 55 } 56 if (fstat_stat.st_dev != stat_stat.st_dev || fstat_stat.st_ino != stat_stat.st_ino) { 57 LOG(WARNING) << "File changed while locking, will retry: " << filename; 58 continue; 59 } 60 return true; 61 } 62 } 63 64 bool ScopedFlock::Init(File* file, std::string* error_msg) { 65 file_.reset(new File(dup(file->Fd()), true)); 66 if (file_->Fd() == -1) { 67 file_.reset(); 68 *error_msg = StringPrintf("Failed to duplicate open file '%s': %s", 69 file->GetPath().c_str(), strerror(errno)); 70 return false; 71 } 72 if (0 != TEMP_FAILURE_RETRY(flock(file_->Fd(), LOCK_EX))) { 73 file_.reset(); 74 *error_msg = StringPrintf( 75 "Failed to lock file '%s': %s", file->GetPath().c_str(), strerror(errno)); 76 return false; 77 } 78 return true; 79 } 80 81 File* ScopedFlock::GetFile() { 82 CHECK(file_.get() != nullptr); 83 return file_.get(); 84 } 85 86 bool ScopedFlock::HasFile() { 87 return file_.get() != nullptr; 88 } 89 90 ScopedFlock::ScopedFlock() { } 91 92 ScopedFlock::~ScopedFlock() { 93 if (file_.get() != nullptr) { 94 int flock_result = TEMP_FAILURE_RETRY(flock(file_->Fd(), LOCK_UN)); 95 CHECK_EQ(0, flock_result); 96 if (file_->FlushCloseOrErase() != 0) { 97 PLOG(WARNING) << "Could not close scoped file lock file."; 98 } 99 } 100 } 101 102 } // namespace art 103