[llvm] f51bc4f - [Support] Add file lock/unlock functions
Serge Pavlov via llvm-commits
llvm-commits at lists.llvm.org
Tue Jun 2 22:23:50 PDT 2020
Author: Serge Pavlov
Date: 2020-06-03T12:22:45+07:00
New Revision: f51bc4fb60fbcef26d18eff549fc68307fd46489
URL: https://github.com/llvm/llvm-project/commit/f51bc4fb60fbcef26d18eff549fc68307fd46489
DIFF: https://github.com/llvm/llvm-project/commit/f51bc4fb60fbcef26d18eff549fc68307fd46489.diff
LOG: [Support] Add file lock/unlock functions
New functions `lockFile`, `tryLockFile` and `unlockFile` implement
simple file locking. They lock or unlock entire file. This must be
enough to support simulataneous writes to log files in parallel builds.
Differential Revision: https://reviews.llvm.org/D78896
Added:
Modified:
llvm/include/llvm/Support/FileSystem.h
llvm/lib/Support/Unix/Path.inc
llvm/lib/Support/Windows/Path.inc
llvm/unittests/Support/Path.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/Support/FileSystem.h b/llvm/include/llvm/Support/FileSystem.h
index a29a9d787947..8014c5c27b25 100644
--- a/llvm/include/llvm/Support/FileSystem.h
+++ b/llvm/include/llvm/Support/FileSystem.h
@@ -1131,6 +1131,39 @@ Expected<file_t>
openNativeFileForRead(const Twine &Name, OpenFlags Flags = OF_None,
SmallVectorImpl<char> *RealPath = nullptr);
+/// Try to locks the file during the specified time.
+///
+/// This function implements advisory locking on entire file. If it returns
+/// <em>errc::success</em>, the file is locked by the calling process. Until the
+/// process unlocks the file by calling \a unlockFile, all attempts to lock the
+/// same file will fail/block. The process that locked the file may assume that
+/// none of other processes read or write this file, provided that all processes
+/// lock the file prior to accessing its content.
+///
+/// @param File The descriptor representing the file to lock.
+/// @param Timeout Time in milliseconds that the process should wait before
+/// reporting lock failure. Zero value means try to get lock only
+/// once.
+/// @returns errc::success if lock is successfully obtained,
+/// errc::no_lock_available if the file cannot be locked, or platform-specific
+/// error_code otherwise.
+std::error_code
+tryLockFile(int FD,
+ std::chrono::milliseconds Timeout = std::chrono::milliseconds(0));
+
+/// Lock the file.
+///
+/// This function acts as @ref tryLockFile(int,std::chrono::milliseconds) but it
+/// waits infinitely.
+std::error_code lockFile(int FD);
+
+/// Unlock the file.
+///
+/// @param File The descriptor representing the file to unlock.
+/// @returns errc::success if lock is successfully released or platform-specific
+/// error_code otherwise.
+std::error_code unlockFile(int FD);
+
/// @brief Close the file object. This should be used instead of ::close for
/// portability. On error, the caller should assume the file is closed, as is
/// the case for Process::SafelyCloseFileDescriptor
diff --git a/llvm/lib/Support/Unix/Path.inc b/llvm/lib/Support/Unix/Path.inc
index bf720b318ded..cab31f92984e 100644
--- a/llvm/lib/Support/Unix/Path.inc
+++ b/llvm/lib/Support/Unix/Path.inc
@@ -33,6 +33,7 @@
#include <dirent.h>
#include <pwd.h>
+#include <sys/file.h>
#ifdef __APPLE__
#include <mach-o/dyld.h>
@@ -1047,6 +1048,34 @@ Expected<size_t> readNativeFileSlice(file_t FD, MutableArrayRef<char> Buf,
return NumRead;
}
+std::error_code tryLockFile(int FD, std::chrono::milliseconds Timeout) {
+ auto Start = std::chrono::steady_clock::now();
+ auto End = Start + Timeout;
+ do {
+ if (::flock(FD, LOCK_EX | LOCK_NB) == 0)
+ return std::error_code();
+ int Error = errno;
+ if (Error == EWOULDBLOCK) {
+ usleep(1000);
+ continue;
+ }
+ return std::error_code(Error, std::generic_category());
+ } while (std::chrono::steady_clock::now() < End);
+ return make_error_code(errc::no_lock_available);
+}
+
+std::error_code lockFile(int FD) {
+ if (::flock(FD, LOCK_EX) == 0)
+ return std::error_code();
+ return std::error_code(errno, std::generic_category());
+}
+
+std::error_code unlockFile(int FD) {
+ if (::flock(FD, LOCK_UN) == -1)
+ return std::error_code(errno, std::generic_category());
+ return std::error_code();
+}
+
std::error_code closeFile(file_t &F) {
file_t TmpF = F;
F = kInvalidFile;
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index ec62e656ddf0..39af3a5f46b6 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -1255,6 +1255,43 @@ Expected<size_t> readNativeFileSlice(file_t FileHandle,
return readNativeFileImpl(FileHandle, Buf, &Overlapped);
}
+std::error_code tryLockFile(int FD, std::chrono::milliseconds Timeout) {
+ DWORD Flags = LOCKFILE_EXCLUSIVE_LOCK | LOCKFILE_FAIL_IMMEDIATELY;
+ OVERLAPPED OV = {0};
+ file_t File = convertFDToNativeFile(FD);
+ auto Start = std::chrono::steady_clock::now();
+ auto End = Start + Timeout;
+ do {
+ if (::LockFileEx(File, Flags, 0, MAXDWORD, MAXDWORD, &OV))
+ return std::error_code();
+ DWORD Error = ::GetLastError();
+ if (Error == ERROR_LOCK_VIOLATION) {
+ ::Sleep(1);
+ continue;
+ }
+ return mapWindowsError(Error);
+ } while (std::chrono::steady_clock::now() < End);
+ return mapWindowsError(ERROR_LOCK_VIOLATION);
+}
+
+std::error_code lockFile(int FD) {
+ DWORD Flags = LOCKFILE_EXCLUSIVE_LOCK;
+ OVERLAPPED OV = {0};
+ file_t File = convertFDToNativeFile(FD);
+ if (::LockFileEx(File, Flags, 0, MAXDWORD, MAXDWORD, &OV))
+ return std::error_code();
+ DWORD Error = ::GetLastError();
+ return mapWindowsError(Error);
+}
+
+std::error_code unlockFile(int FD) {
+ OVERLAPPED OV = {0};
+ file_t File = convertFDToNativeFile(FD);
+ if (::UnlockFileEx(File, 0, MAXDWORD, MAXDWORD, &OV))
+ return std::error_code();
+ return mapWindowsError(::GetLastError());
+}
+
std::error_code closeFile(file_t &F) {
file_t TmpF = F;
F = kInvalidFile;
diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index 8e842a95b2b2..92b3917724ff 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -39,6 +39,8 @@
#include <sys/stat.h>
#endif
+#include <future>
+
using namespace llvm;
using namespace llvm::sys;
@@ -2038,4 +2040,47 @@ TEST_F(FileSystemTest, widenPath) {
}
#endif
+TEST_F(FileSystemTest, lockFile) {
+ int FD1, FD2;
+ SmallString<64> TempPath;
+ ASSERT_NO_ERROR(fs::createTemporaryFile("test", "temp", FD1, TempPath));
+ FileRemover Cleanup(TempPath);
+ ASSERT_NO_ERROR(fs::openFileForReadWrite(TempPath, FD2, fs::CD_OpenExisting,
+ fs::OF_Append));
+ ASSERT_NO_ERROR(fs::tryLockFile(FD1));
+
+ ASSERT_EQ(errc::no_lock_available,
+ fs::tryLockFile(FD2, std::chrono::milliseconds(5)));
+ ASSERT_NO_ERROR(fs::unlockFile(FD1));
+ ASSERT_NO_ERROR(fs::tryLockFile(FD2));
+ ASSERT_NO_ERROR(fs::unlockFile(FD2));
+}
+
+TEST_F(FileSystemTest, lockFileThread) {
+#if LLVM_ENABLE_THREADS
+ int FD1, FD2;
+ SmallString<64> TempPath;
+ ASSERT_NO_ERROR(fs::createTemporaryFile("test", "temp", FD1, TempPath));
+ FileRemover Cleanup(TempPath);
+ ASSERT_NO_ERROR(fs::openFileForReadWrite(TempPath, FD2, fs::CD_OpenExisting,
+ fs::OF_Append));
+
+ ASSERT_NO_ERROR(fs::tryLockFile(FD1));
+ ASSERT_ERROR(fs::tryLockFile(FD2));
+ std::future<std::error_code> Future = std::async(std::launch::async, [&] {
+ return fs::tryLockFile(FD2, std::chrono::seconds(5));
+ });
+ ASSERT_NO_ERROR(fs::unlockFile(FD1));
+ ASSERT_NO_ERROR(Future.get());
+ fs::unlockFile(FD2);
+
+ ASSERT_NO_ERROR(fs::tryLockFile(FD1));
+ ASSERT_ERROR(fs::tryLockFile(FD2));
+ Future = std::async(std::launch::async, [&] { return fs::lockFile(FD2); });
+ ASSERT_NO_ERROR(fs::unlockFile(FD1));
+ ASSERT_NO_ERROR(Future.get());
+ fs::unlockFile(FD2);
+#endif
+}
+
} // anonymous namespace
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