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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2017 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
// Package snaplock offers per-snap locking also used by snap-confine.
// The corresponding C code is in libsnap-confine-private/locking.c
package snaplock
import (
"fmt"
"os"
"path/filepath"
"github.com/snapcore/snapd/dirs"
"github.com/snapcore/snapd/osutil"
)
// lockFileName returns the name of the lock file for the given snap.
func lockFileName(snapName string) string {
return filepath.Join(dirs.SnapRunLockDir, fmt.Sprintf("%s.lock", snapName))
}
// OpenLock creates and opens a lock file associated with a particular snap.
//
// NOTE: The snap lock is only accessible to root and is only intended to
// synchronize operations between snapd and snap-confine (and snap-update-ns
// in some cases). Any process holding the snap lock must not do any
// interactions with snapd to avoid deadlocks due to locked snap state.
func OpenLock(snapName string) (*osutil.FileLock, error) {
if err := os.MkdirAll(dirs.SnapRunLockDir, 0700); err != nil {
return nil, fmt.Errorf("cannot create lock directory: %s", err)
}
flock, err := osutil.NewFileLock(lockFileName(snapName))
if err != nil {
return nil, err
}
return flock, nil
}
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