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authorRichard Purdie <richard@openedhand.com>2007-11-24 14:44:36 +0000
committerRichard Purdie <richard@openedhand.com>2007-11-24 14:44:36 +0000
commit701aa74aeb2e06368a927b4b61dd02160066101a (patch)
treef5e0ffdd16f423883d2ab0e64632afa551b9d323 /bitbake
parent4aaa8343bc1394d58ca6017d46bf11c1f151fae6 (diff)
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bitbake: Add bb.utils.lockfile() and bb.utils.unlockfile()
git-svn-id: https://svn.o-hand.com/repos/poky/trunk@3221 311d38ba-8fff-0310-9ca6-ca027cbcb966
Diffstat (limited to 'bitbake')
-rw-r--r--bitbake/lib/bb/utils.py37
1 files changed, 36 insertions, 1 deletions
diff --git a/bitbake/lib/bb/utils.py b/bitbake/lib/bb/utils.py
index c2884f263..c27dafd61 100644
--- a/bitbake/lib/bb/utils.py
+++ b/bitbake/lib/bb/utils.py
@@ -22,7 +22,7 @@ BitBake Utility Functions
digits = "0123456789"
ascii_letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
-import re
+import re, fcntl, os
def explode_version(s):
r = []
@@ -202,3 +202,38 @@ def Enum(*names):
constants = tuple(constants)
EnumType = EnumClass()
return EnumType
+
+def lockfile(name):
+ """
+ Use the file fn as a lock file, return when the lock has been aquired.
+ Returns a variable to pass to unlockfile().
+ """
+ while True:
+ # If we leave the lockfiles lying around there is no problem
+ # but we should clean up after ourselves. This gives potential
+ # for races though. To work around this, when we aquire the lock
+ # we check the file we locked was still the lock file on disk.
+ # by comparing inode numbers. If they don't match or the lockfile
+ # no longer exists, we start again.
+
+ # This implementation is unfair since the last person to request the
+ # lock is the most likely to win it.
+
+ lf = open(name, "a+")
+ fcntl.flock(lf.fileno(), fcntl.LOCK_EX)
+ statinfo = os.fstat(lf.fileno())
+ if os.path.exists(lf.name):
+ statinfo2 = os.stat(lf.name)
+ if statinfo.st_ino == statinfo2.st_ino:
+ return lf
+ # File no longer exists or changed, retry
+ lf.close
+
+def unlockfile(lf):
+ """
+ Unlock a file locked using lockfile()
+ """
+ os.unlink(lf.name)
+ fcntl.flock(lf.fileno(), fcntl.LOCK_UN)
+ lf.close
+