github.com/containerd/Containerd@v1.4.13/content/local/locks.go (about)

     1  /*
     2     Copyright The containerd Authors.
     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  package local
    18  
    19  import (
    20  	"sync"
    21  
    22  	"github.com/containerd/containerd/errdefs"
    23  	"github.com/pkg/errors"
    24  )
    25  
    26  // Handles locking references
    27  
    28  var (
    29  	// locks lets us lock in process
    30  	locks   = map[string]struct{}{}
    31  	locksMu sync.Mutex
    32  )
    33  
    34  func tryLock(ref string) error {
    35  	locksMu.Lock()
    36  	defer locksMu.Unlock()
    37  
    38  	if _, ok := locks[ref]; ok {
    39  		return errors.Wrapf(errdefs.ErrUnavailable, "ref %s locked", ref)
    40  	}
    41  
    42  	locks[ref] = struct{}{}
    43  	return nil
    44  }
    45  
    46  func unlock(ref string) {
    47  	locksMu.Lock()
    48  	defer locksMu.Unlock()
    49  
    50  	delete(locks, ref)
    51  }