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Date: Tue, 14 Sep 2010 19:07:53 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
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Subject: Re: Deletion race in NtSetFileInformation ? (Directory not empty error in rm -r -f)
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On Sep 14 09:39, Earl Chew wrote:
> > There shouldn't be any race.  When you set the delete disposition,
> > the file is actually deleted as soon as the last handle to the file
> > is closed.  If the file isn't opened by another process, it will
> > disappear right at the NtClose at the end of unlink_nt.  Please note
> > that the call to check_dir_not_empty already takes place *only* if
> > trying to open the directory failed with STATUS_SHARING_VIOLATION.
> > So there *was* another process blocking things.
> 
> Corinna,
> 
> Yes, I noticed that check wrt STATUS_SHARING_VIOLATION.
> 
> These actions are performed consequential to a shell script,
> that launches a Makefile, that performs the rm -r -f ... so within
> that context there is definitely scope for oversight and we
> might inadvertently have a process getting in the way.
> 
> When you describe the other process blocking things, what might
> that other process be doing?
> 
> I presume that other process having the directory in question
> open, or as cwd is sufficient.

...or having a cwd below the directory.  Trying to remove a directory
which is the CWD of some process is the most common reason that the
directory is blocked, because the Win32 CWD is opened without the
FILE_SHARE_DELETE flag.  Especially something like `rm -rf ../foo'
is suspicious, if foo is the CWD of the current shell.

We're trying to revert this to the Linux way again in 1.7.8 (see the
thread starting at http://cygwin.com/ml/cygwin/2010-09/msg00342.html),
but even after that the problem remains for any non-Cygwin process.

> Is there anything else I should be on the lookout for?

Virus scanners, etc.  There *might* be some unfortunate interaction
with a scanner which keeps handles of just deleted files or dirs open.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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