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Re: untarring symlinks with ../ fails randomly, silghtly OT
On Tue, 2011-07-05 at 08:21 -0400, Ryan Johnson wrote:
> On 05/07/2011 8:10 AM, Corinna Vinschen wrote:
> > On Jul 4 12:46, Corinna Vinschen wrote:
> >> On Jul 4 11:15, Wolf Geldmacher wrote:
> >>> As an aside:
> >>> I also used to have some trouble with "rm -rf" of a directory
> >>> hierarchy failing more or less reproducibly (like: 80% of the
> >>> time) because files were presumably still "in use". Repeating
> >>> the command several times would succeed, though.
> >>>
> >>> Downgrading from cygwin1.dll/1.7.9.1 to cygwin1.dll/1.7.8.1
> >>> seems to have solved that issue as well - still have to see
> >>> the first "retry to delete".
> >>>
> >>> This may or may not be related to the original report, as it also reeks
> >>> of a race condition during file/directory operations.
> >> I can neither reproduce the tar problem, nor can I reprocude the rm
> >> problem. I tried this under 2008R2 which is basically the same as your
> >> W7-64 bit. I used local and remote drives to test the issue but to no
> >> avail.
> > Finally I managed to reproduce the problem and now I see what happens.
> >
> > Windows does not write back the file change timestamp unless the file
> > buffers are flushed. This usually occurs at close time. In contrast to
> > POSIX specifications the timestamps are *not* automatically updated when
> > a call to fetch file metadata is performed.
> >
> > Here's what tar does when creating the symlink:
> >
> > 1. create file with 000 permissions
> > 2. fstat
> > 3. close file
> > [...]
> > 4. stat file
> > 5. if fstat.st_ctime != stat.st_ctime ==> symlink placeholder has been
> > overwritten.
> >
> > The problem is that the call to fstat on the opened handle gets some
> > value of the change time timestamp, but the subsequent close changes
> > the timestamp again.
> Wow. That must have been one hairy debug session... my hat goes off to you!
>
> Ryan
Definitely agree! (Where's the "Like" button?)
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