From: Chris Larson <chris_larson@mentor.com>
Date: Tue, 8 Mar 2011 16:33:40 +0000 (-0700)
Subject: lockfile: ask for forgiveness, not permission
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=238151441c74db53d6e4d4753f4f96c32f6f13b6;p=thirdparty%2Fopenembedded%2Fopenembedded-core-contrib.git

lockfile: ask for forgiveness, not permission

Create the lockfile directory if it doesn't exist, rather than erroring out if
it doesn't exist (was also racy).

Also improve the wording of the error message shown when the lockfile's
directory is not writable.

Note for the future, this function should be improved, particularly with
regard to its exception handling. It should be catching the *exact*
exception(s) it will encounter when the file is locked, and continuing in that
case only. If it did that, there'd be no need for the proactive directory
writability check, as bb.utils.lockfile() would raise an appropriate IOError
for that case.

Signed-off-by: Chris Larson <chris_larson@mentor.com>
---

diff --git a/lib/bb/utils.py b/lib/bb/utils.py
index 44419d8f2a6..5a4e5731d5d 100644
--- a/lib/bb/utils.py
+++ b/lib/bb/utils.py
@@ -407,13 +407,12 @@ def lockfile(name, shared=False):
     Use the file fn as a lock file, return when the lock has been acquired.
     Returns a variable to pass to unlockfile().
     """
-    path = os.path.dirname(name)
-    if not os.path.isdir(path):
-        logger.error("Lockfile destination directory '%s' does not exist", path)
-        sys.exit(1)
+    dirname = os.path.dirname(name)
+    mkdirhier(dirname)
 
-    if not os.access(path, os.W_OK):
-        logger.error("Error, lockfile path is not writable!: %s" % path)
+    if not os.access(dirname, os.W_OK):
+        logger.error("Unable to acquire lock '%s', directory is not writable",
+                     dirname)
         sys.exit(1)
 
     op = fcntl.LOCK_EX
@@ -449,7 +448,7 @@ def unlockfile(lf):
     Unlock a file locked using lockfile()
     """
     try:
-        # If we had a shared lock, we need to promote to exclusive before 
+        # If we had a shared lock, we need to promote to exclusive before
         # removing the lockfile. Attempt this, ignore failures.
         fcntl.flock(lf.fileno(), fcntl.LOCK_EX|fcntl.LOCK_NB)
         os.unlink(lf.name)