[Ironpython-users] struct.pack(format, *args) not thread safe

[Michael van der Kolff]

When using paramiko with more than one process spawning, I
occasionally get the following:

System.InvalidOperationException: The LinkedList node already belongs
to a LinkedList.
   at System.Collections.Generic.LinkedList`1.ValidateNewNode(LinkedListNode`1
node)   at System.Collections.Generic.LinkedList`1.AddFirst(LinkedListNode`1
node)
   at IronPython.Modules.PythonStruct.pack(CodeContext context, String
fmt, Object[] values)
   at CallSite.Target(Closure , CallSite , CodeContext , Object ,
String , Object )
   at paramiko.message$37.add_int$491(PythonFunction $function, Object
self, Object n) in
C:\repo\trunk\external\python\paramiko\message.py:line 227
   at paramiko.message$37.add_string$494(PythonFunction $function,
Object self, Object s) in
C:\repo\trunk\external\python\paramiko\message.py:line 259
   at paramiko.transport$13.open_channel$273(PythonFunction $function,
Object self, Object kind, Object dest_addr, Object src_addr) in
C:\repo\trunk\external\python\paramiko\transport.py:line 773
   ... Lots more in the stack trace.

I think that this is due to PythonStruct.pack's usage of CacheDict,
which is explicitly marked as not thread safe.  A quick and dirty hack
would be to force all users of _cache to lock it first, though I'm
sure there's a better answer.

Cheers,


Michael