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[Support/LockFileManager] Re-apply r203137 and r203138 but use symbolic links only on unix. 

Reid Kleckner pointed out that we can't use symbolic links on Windows.

llvm-svn: 203162
This commit is contained in:
Argyrios Kyrtzidis 2014-03-06 20:53:58 +00:00
parent 29b82b631d
commit 4147978cc5
1 changed files with 57 additions and 25 deletions
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82
llvm/lib/Support/LockFileManager.cpp
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@ -67,6 +67,22 @@ bool LockFileManager::processStillExecuting(StringRef Hostname, int PID) {
return true;
}
#if LLVM_ON_UNIX
static error_code unix_create_symbolic_link(const Twine &to,
const Twine &from) {
// Get arguments.
SmallString<128> from_storage;
SmallString<128> to_storage;
StringRef f = from.toNullTerminatedStringRef(from_storage);
StringRef t = to.toNullTerminatedStringRef(to_storage);
if (::symlink(t.begin(), f.begin()) == -1)
return error_code(errno, system_category());
return error_code::success();
}
#endif
LockFileManager::LockFileManager(StringRef FileName)
{
this->FileName = FileName;
@ -115,34 +131,50 @@ LockFileManager::LockFileManager(StringRef FileName)
}
}
// Create a hard link from the lock file name. If this succeeds, we're done.
error_code EC
= sys::fs::create_hard_link(UniqueLockFileName.str(),
LockFileName.str());
if (EC == errc::success)
return;
// Creating the hard link failed.
#ifdef LLVM_ON_UNIX
// The creation of the hard link may appear to fail, but if stat'ing the
// unique file returns a link count of 2, then we can still declare success.
struct stat StatBuf;
if (stat(UniqueLockFileName.c_str(), &StatBuf) == 0 &&
StatBuf.st_nlink == 2)
return;
while (1) {
#if LLVM_ON_UNIX
// Create a symbolic link from the lock file name. If this succeeds, we're
// done. Note that we are using symbolic link because hard links are not
// supported by all filesystems.
error_code EC
= unix_create_symbolic_link(UniqueLockFileName.str(),
LockFileName.str());
#else
// We can't use symbolic links for windows.
// Create a hard link from the lock file name. If this succeeds, we're done.
error_code EC
= sys::fs::create_hard_link(UniqueLockFileName.str(),
LockFileName.str());
#endif
if (EC == errc::success)
return;
// Someone else managed to create the lock file first. Wipe out our unique
// lock file (it's useless now) and read the process ID from the lock file.
sys::fs::remove(UniqueLockFileName.str());
if ((Owner = readLockFile(LockFileName)))
return;
if (EC != errc::file_exists) {
Error = EC;
return;
}
// There is a lock file that nobody owns; try to clean it up and report
// an error.
sys::fs::remove(LockFileName.str());
Error = EC;
// Someone else managed to create the lock file first. Read the process ID
// from the lock file.
if ((Owner = readLockFile(LockFileName))) {
// Wipe out our unique lock file (it's useless now)
sys::fs::remove(UniqueLockFileName.str());
return;
}
if (!sys::fs::exists(LockFileName.str())) {
// The previous owner released the lock file before we could read it.
// Try to get ownership again.
continue;
}
// There is a lock file that nobody owns; try to clean it up and get
// ownership.
if ((EC = sys::fs::remove(LockFileName.str()))) {
Error = EC;
return;
}
}
}
LockFileManager::LockFileState LockFileManager::getState() const {