Fix os.mkdir race condition.

This code checks whether a dir exists before creating it. In between the
check and the mkdir call, it is possible that another process will have
created the directory. We have seen this bug occur many times in
practice during our 'repo init' tests.

Change-Id: Ia47d39955739aa38fd303f4e90be7b4c50d9d4ba

1 files changed, 13 insertions, 12 deletions

diff --git a/repo b/repo
index d81cdd60..56d784fb 100755
--- a/repo
+++ b/repo
@@ -110,6 +110,7 @@ REPO_MAIN = S_repo + '/main.py' # main script
 MIN_PYTHON_VERSION = (2, 6)     # minimum supported python version
 
 
+import errno
 import optparse
 import os
 import re
@@ -243,10 +244,10 @@ def _Init(args):
     _print("fatal: invalid branch name '%s'" % branch, file=sys.stderr)
     raise CloneFailure()
 
-  if not os.path.isdir(repodir):
-    try:
-      os.mkdir(repodir)
-    except OSError as e:
+  try:
+    os.mkdir(repodir)
+  except OSError as e:
+    if e.errno != errno.EEXIST:
       _print('fatal: cannot make %s directory: %s'
              % (repodir, e.strerror), file=sys.stderr)
       # Don't raise CloneFailure; that would delete the
@@ -325,18 +326,18 @@ def NeedSetupGnuPG():
 
 
 def SetupGnuPG(quiet):
-  if not os.path.isdir(home_dot_repo):
-    try:
-      os.mkdir(home_dot_repo)
-    except OSError as e:
+  try:
+    os.mkdir(home_dot_repo)
+  except OSError as e:
+    if e.errno != errno.EEXIST:
       _print('fatal: cannot make %s directory: %s'
              % (home_dot_repo, e.strerror), file=sys.stderr)
       sys.exit(1)
 
-  if not os.path.isdir(gpg_dir):
-    try:
-      os.mkdir(gpg_dir, stat.S_IRWXU)
-    except OSError as e:
+  try:
+    os.mkdir(gpg_dir, stat.S_IRWXU)
+  except OSError as e:
+    if e.errno != errno.EEXIST:
       _print('fatal: cannot make %s directory: %s' % (gpg_dir, e.strerror),
              file=sys.stderr)
       sys.exit(1)