From 37fcbfa1f4586e4437664239fc271dda31ac1837 Mon Sep 17 00:00:00 2001
From: James Allen <jamesallen0108@gmail.com>
Date: Wed, 15 Jan 2014 17:29:46 +0000
Subject: [PATCH] Add RWMutex lock into TruncIndex to fix race condition when
 inserting values

The idx.index array is overwritten when a new value is inserted to the index.
When two containers are created concurrently, their ids are inserted to the
index and one can overwrite the other leaving one of ids missing from the
index. Adding a RWMutex lock around read/write operations fixes this.

Docker-DCO-1.1-Signed-off-by: James Allen <jamesallen0108@gmail.com> (github: jpallen)
---
 utils/utils.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/utils/utils.go b/utils/utils.go
index e046dfa2a..25573d46b 100644
--- a/utils/utils.go
+++ b/utils/utils.go
@@ -418,6 +418,7 @@ func GetTotalUsedFds() int {
 // TruncIndex allows the retrieval of string identifiers by any of their unique prefixes.
 // This is used to retrieve image and container IDs by more convenient shorthand prefixes.
 type TruncIndex struct {
+	sync.RWMutex
 	index *suffixarray.Index
 	ids   map[string]bool
 	bytes []byte
@@ -432,6 +433,8 @@ func NewTruncIndex() *TruncIndex {
 }
 
 func (idx *TruncIndex) Add(id string) error {
+	idx.Lock()
+	defer idx.Unlock()
 	if strings.Contains(id, " ") {
 		return fmt.Errorf("Illegal character: ' '")
 	}
@@ -445,6 +448,8 @@ func (idx *TruncIndex) Add(id string) error {
 }
 
 func (idx *TruncIndex) Delete(id string) error {
+	idx.Lock()
+	defer idx.Unlock()
 	if _, exists := idx.ids[id]; !exists {
 		return fmt.Errorf("No such id: %s", id)
 	}
@@ -470,6 +475,8 @@ func (idx *TruncIndex) lookup(s string) (int, int, error) {
 }
 
 func (idx *TruncIndex) Get(s string) (string, error) {
+	idx.RLock()
+	defer idx.RUnlock()
 	before, after, err := idx.lookup(s)
 	//log.Printf("Get(%s) bytes=|%s| before=|%d| after=|%d|\n", s, idx.bytes, before, after)
 	if err != nil {