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
Init(const char * filename,std::string * error_msg)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
Init(File * file,std::string * error_msg)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
GetFile()77 File* ScopedFlock::GetFile() {
78 CHECK(file_.get() != NULL);
79 return file_.get();
80 }
81
HasFile()82 bool ScopedFlock::HasFile() {
83 return file_.get() != nullptr;
84 }
85
ScopedFlock()86 ScopedFlock::ScopedFlock() { }
87
~ScopedFlock()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