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
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@ -22,7 +22,7 @@ BitBake Utility Functions
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digits = "0123456789"
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ascii_letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
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import re
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import re, fcntl, os
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def explode_version(s):
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r = []
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@ -202,3 +202,38 @@ def Enum(*names):
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constants = tuple(constants)
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EnumType = EnumClass()
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return EnumType
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def lockfile(name):
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"""
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Use the file fn as a lock file, return when the lock has been aquired.
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Returns a variable to pass to unlockfile().
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"""
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while True:
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# If we leave the lockfiles lying around there is no problem
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# but we should clean up after ourselves. This gives potential
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# for races though. To work around this, when we aquire the lock
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# we check the file we locked was still the lock file on disk.
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# by comparing inode numbers. If they don't match or the lockfile
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# no longer exists, we start again.
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# This implementation is unfair since the last person to request the
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# lock is the most likely to win it.
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lf = open(name, "a+")
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fcntl.flock(lf.fileno(), fcntl.LOCK_EX)
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statinfo = os.fstat(lf.fileno())
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if os.path.exists(lf.name):
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statinfo2 = os.stat(lf.name)
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if statinfo.st_ino == statinfo2.st_ino:
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return lf
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# File no longer exists or changed, retry
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lf.close
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def unlockfile(lf):
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"""
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Unlock a file locked using lockfile()
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"""
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os.unlink(lf.name)
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fcntl.flock(lf.fileno(), fcntl.LOCK_UN)
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lf.close
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