From 6915fe26da8dce41fc967d761f005390aa956161 Mon Sep 17 00:00:00 2001
From: Michael Hanselmann <hansmi@google.com>
Date: Thu, 13 Oct 2011 19:04:37 +0200
Subject: [PATCH] utils.cfunc: Cleanup, more flexibility
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- Split code using ctypes directly into a helper class
- Don't load βlibc.so.6β, but use handle for main program instead (see
comment in code)
- Clarify comment on errno with older ctypes versions
- Rename unittest since it can't be used for other functions (modifies
process environment at runtime)
- Add boolean return value for βMlockallβ
These changes are leftovers from some experiments with ctypes.
Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>
---
Makefile.am | 2 +-
lib/utils/cfunc.py | 73 ++++++++++++-------
...> ganeti.utils.cfunc.mlockall_unittest.py} | 4 +-
3 files changed, 47 insertions(+), 32 deletions(-)
rename test/{ganeti.utils.cfunc_unittest.py => ganeti.utils.cfunc.mlockall_unittest.py} (97%)
diff --git a/Makefile.am b/Makefile.am
index 2a513f15f..5031a5303 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -724,7 +724,7 @@ python_tests = \
test/ganeti.tools.ensure_dirs_unittest.py \
test/ganeti.uidpool_unittest.py \
test/ganeti.utils.algo_unittest.py \
- test/ganeti.utils.cfunc_unittest.py \
+ test/ganeti.utils.cfunc.mlockall_unittest.py \
test/ganeti.utils.filelock_unittest.py \
test/ganeti.utils.hash_unittest.py \
test/ganeti.utils.io_unittest.py \
diff --git a/lib/utils/cfunc.py b/lib/utils/cfunc.py
index ea14d6848..a1b3af49b 100644
--- a/lib/utils/cfunc.py
+++ b/lib/utils/cfunc.py
@@ -34,44 +34,61 @@ except ImportError:
ctypes = None
-# Flags for mlockall() (from bits/mman.h)
+# Flags for mlockall(2) (from bits/mman.h)
_MCL_CURRENT = 1
_MCL_FUTURE = 2
+class _FuncWrapper:
+ def __init__(self, ct):
+ """Initializes this class.
+
+ """
+ # Make use of a dlopen(3) feature whereby giving a NULL handle returns the
+ # main program. Functions from all previously loaded libraries can then be
+ # used.
+ mainprog = ct.CDLL(None)
+
+ # The ctypes module before Python 2.6 does not have built-in functionality
+ # to access the global errno global (which, depending on the libc and build
+ # options, is per-thread), where function error codes are stored. Use GNU
+ # libc's way to retrieve errno(3) instead.
+ try:
+ errno_loc = getattr(mainprog, "__errno_location")
+ except AttributeError, err:
+ logging.debug("Unable to find errno location: %s", err)
+ errno_fn = None
+ else:
+ errno_loc.restype = ct.POINTER(ct.c_int)
+ errno_fn = lambda: errno_loc().contents.value
+
+ self.errno_fn = errno_fn
+
+ # Try to get mlockall(2)
+ self.mlockall_fn = getattr(mainprog, "mlockall", None)
+
+
def Mlockall(_ctypes=ctypes):
"""Lock current process' virtual address space into RAM.
- This is equivalent to the C call mlockall(MCL_CURRENT|MCL_FUTURE),
- see mlock(2) for more details. This function requires ctypes module.
+ This is equivalent to the C call C{mlockall(MCL_CURRENT | MCL_FUTURE)}. See
+ mlockall(2) for more details. This function requires the C{ctypes} module.
- @raises errors.NoCtypesError: if ctypes module is not found
+ @raises errors.NoCtypesError: If the C{ctypes} module is not found
"""
if _ctypes is None:
raise errors.NoCtypesError()
- try:
- libc = _ctypes.cdll.LoadLibrary("libc.so.6")
- except EnvironmentError, err:
- logging.error("Failure trying to load libc: %s", err)
- libc = None
- if libc is None:
- logging.error("Cannot set memory lock, ctypes cannot load libc")
- return
-
- # Some older version of the ctypes module don't have built-in functionality
- # to access the errno global variable, where function error codes are stored.
- # By declaring this variable as a pointer to an integer we can then access
- # its value correctly, should the mlockall call fail, in order to see what
- # the actual error code was.
- # pylint: disable=W0212
- libc.__errno_location.restype = _ctypes.POINTER(_ctypes.c_int)
-
- if libc.mlockall(_MCL_CURRENT | _MCL_FUTURE):
- # pylint: disable=W0212
- logging.error("Cannot set memory lock: %s",
- os.strerror(libc.__errno_location().contents.value))
- return
-
- logging.debug("Memory lock set")
+ funcs = _FuncWrapper(_ctypes)
+
+ if funcs.mlockall_fn is None:
+ logging.debug("libc doesn't support mlockall(2)")
+ else:
+ if funcs.mlockall_fn(_MCL_CURRENT | _MCL_FUTURE) == 0:
+ logging.debug("Memory lock set")
+ return True
+
+ logging.error("Cannot set memory lock: %s", os.strerror(funcs.errno_fn()))
+
+ return False
diff --git a/test/ganeti.utils.cfunc_unittest.py b/test/ganeti.utils.cfunc.mlockall_unittest.py
similarity index 97%
rename from test/ganeti.utils.cfunc_unittest.py
rename to test/ganeti.utils.cfunc.mlockall_unittest.py
index 8c5c7469b..bafa71c8d 100755
--- a/test/ganeti.utils.cfunc_unittest.py
+++ b/test/ganeti.utils.cfunc.mlockall_unittest.py
@@ -41,17 +41,15 @@ class TestMlockallWithCtypes(unittest.TestCase):
"""Whether Mlockall() works if ctypes is present.
"""
-
def test(self):
if utils.ctypes:
- utils.Mlockall()
+ self.assertTrue(utils.Mlockall())
class TestMlockallWithNoCtypes(unittest.TestCase):
"""Whether Mlockall() raises an error if ctypes is not present.
"""
-
def test(self):
self.assertRaises(errors.NoCtypesError, utils.Mlockall, _ctypes=None)
--
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