ftruncate() may fail with EISDIR if other process calls open()

[Christian Franke]

Corinna Vinschen via Cygwin wrote:
> On Apr  8 13:50, Corinna Vinschen via Cygwin wrote:
>> On Apr  7 09:59, Christian Franke via Cygwin wrote:
>>> Found because 'stress-ng --fcntl 2 --verify' reports "ftruncate failed,
>>> errno=21":
>> Thanks for the testcase.  I know what happens.  Stay tuned for a patch.
> Nice problem.  That's what happens if you try to do what an OS is doing,
> without actually being an OS, just a user space lib.  Theoretically we
> should never cache any file information but always call the matching OS
> functions.  Only... this adds quite a few context switches every time
> accessing files.  Sigh.
>
> I just pushed 2d81f6ebe3dc ("Cygwin: open: always fix up cached DOS file
> attributes after NtCreateFile").
>
> Try the upcoming cygwin-3.7.0-0.47.g9e6193576f34.

With a local build of 3.7.0-dev-49-g42df80dad079.x86_64, both the 
testcase and stress-ng no longer fail.

-- 
Regards,
Christian