Threading issue: [Error 9]: bad file descriptor

[David Bolen]

"Kevin" <other at cazabon.com> writes:

> My oversight, thanks!
> 
> I'm testing on Windows 2000 Professional, but have had other users report
> the same problem on other Windows flavours (NT, 98).

I can only speak for NT, but I have seen timing issues in the past
where there is some additional latency imposed by the system between
when I release all references to a file and when it can be removed
from the filesystem by the same process.  This has affected me in C
code as well as Python.  Perhaps you're running into the same thing,
although for me it normally showed up as a permission denied error.

Sometimes the higher level Python I/O exceptions can be a bit vague
(by their nature, a lot of underlying Win32 error codes eventually get
translated into a far fewer number of C RTL error codes, which in turn
bubble up as Python exceptions).  One thing you could try, depending
on the operation in question, is to replace the Python operation (such
as os.remove) with a matching win32all module operation (such as
win32file.DeleteFile), which should raise a more specific exception.

In my past experiences, the most practical, albeit inelegant,
workaround was to retry a failed removal operation after several
seconds.  Definitely a kluge, but I was never able to isolate any more
well-defined approach.

This of course assumes that you don't really have a threading race
condition under which you still do hold active handles to the file
that you are trying to remove.  The fact that you're getting back an
invalid handle error certainly makes it seem that you make still be
looking at a race condition or inter-thread data corruption within
your application.

Depending on the structure of the application, if you can wrap (or if
you have already) all access to your file handles through a common
class you should be able to instrument it in order to at least get
some sort of trace as to how they are accessed, and perhaps catch one
of the failures.  But as you probably know, debugging this sort of
thing can be nasty, particularly if it's truly sporadic in nature.

-- David