On 03/10/2013 4:55 PM, Adam Kellas wrote:
My company uses Cygwin and we experience fairly frequent fork
failures, believed to be BLODA-related. I say "believed to be" because
in this corporate environment, like many, we cannot uninstall the
virus scanner even long enough to see what happens without it. The
presumed culprit in our case is Microsoft Forefront Endpoint
Protection, by the way.
So we need Cygwin and we're stuck with Forefront, putting us between a
rock and a hard place. It's clear from the documentation and mailing
list that the official stance wrt BLODA is "sorry, can't help you" and
I understand and accept that. I'm looking for the answer to a related
question: are BLODA-caused fork failures a logically unsolvable
problem due to the way Windows works or is it just a matter of round
tuits? In other words, if we were (hypothetically) able to pay someone
to make MS Forefront and Cygwin play nicely together, would that have
a chance of success? And would the Cygwin maintainers allow such work
into the code base or consider it an unfortunate precedent?
I can't comment on actual code changes, but having played around quite a bit
in the fork code, I can at least speak a little to the technical part.
BLODA commonly causes two classes of symptoms:
1. Fork failures due to injecting dlls at inopportune locations or otherwise
messing with address space layouts in a way that violates posix semantics
(memory-mapping a file where some cygwin dll should have gone, for example).
Cygwin can do nothing, because the damage is invariably done before
cygwin1.dll loads. The problem can only be fixed if the BLODA were to be
more circumspect about where it injects things, which is unlikely because
Windows processes normally care very little (if at all) about address space
layouts.
2. Various file-related errors due to the BLODA touching/locking files at
inopportune times (e.g. right when a cygwin process tries to delete the
file, leading to an "unable to delete" error). This is simple Windows
locking at play, which Cygwin actually respects (unlike many Windows
programs). Again, there's little cygwin can do to address the problem on its
side, because the file really is locked...
... all of which is the long way of explaining why the official stance is
"sorry, you're SOL" ...