# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1272962142 -3600
# Node ID ca9519f09563566977d8009b347b93cd01d9089f
# Parent e1482f91b235428a6f7dab8da4b651520b3e6c94
Remus: add file locking and modprobe utility functions
Signed-off-by: Brendan Cully <brendan@xxxxxxxxx>
---
tools/python/xen/remus/util.py | 51 ++++++++++++++++++++++++++++++++++++++++-
1 files changed, 50 insertions(+), 1 deletion(-)
diff -r e1482f91b235 -r ca9519f09563 tools/python/xen/remus/util.py
--- a/tools/python/xen/remus/util.py Tue May 04 09:35:18 2010 +0100
+++ b/tools/python/xen/remus/util.py Tue May 04 09:35:42 2010 +0100
@@ -1,6 +1,6 @@
# utility functions
-import os, subprocess
+import fcntl, os, subprocess
class PipeException(Exception):
def __init__(self, message, errno):
@@ -8,8 +8,49 @@ class PipeException(Exception):
message = '%s: %d, %s' % (message, errno, os.strerror(errno))
Exception.__init__(self, message)
+class Lock(object):
+ """advisory lock"""
+
+ def __init__(self, filename):
+ """lock using filename for synchronization"""
+ self.filename = filename + '.lock'
+
+ self.fd = None
+
+ self.lock()
+
+ def __del__(self):
+ self.unlock()
+
+ def lock(self):
+ if self.fd:
+ return
+
+ self.fd = open(self.filename, 'w')
+ fcntl.lockf(self.fd, fcntl.LOCK_EX)
+
+ def unlock(self):
+ if not self.fd:
+ return
+
+ fcntl.lockf(self.fd, fcntl.LOCK_UN)
+ self.fd = None
+ try:
+ os.remove(self.filename)
+ except OSError:
+ # harmless race
+ pass
+
def canonifymac(mac):
return ':'.join(['%02x' % int(field, 16) for field in mac.split(':')])
+
+def checkpid(pid):
+ """return True if pid is live"""
+ try:
+ os.kill(pid, 0)
+ return True
+ except OSError:
+ return False
def runcmd(args, cwd=None):
# TODO: stdin handling
@@ -29,3 +70,11 @@ def runcmd(args, cwd=None):
return stdout
except (OSError, IOError), inst:
raise PipeException('could not run %s' % args[0], inst.errno)
+
+def modprobe(modname):
+ """attempt to load kernel module modname"""
+ try:
+ runcmd(['modprobe', '-q', modname])
+ return True
+ except PipeException:
+ return False
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