Re: [PATCH] Cygwin: open: Add missing unlock on error

Hi Mark,

On Mon, 3 Aug 2026, Mark Geisert wrote:

> On 8/3/2026 12:36 PM, Johannes Schindelin wrote:
> > 
> > I independently reviewed this and reached the same conclusion: the fix
> > is correct and minimal. I see it already landed on master as
> > 0d3ea0ee653f (with Mark's Reviewed-by), so it's kind of a belated
> > review.
> > 
> > On Mon, 3 Aug 2026, Takashi Yano wrote:
> > 
> > > the commit 524d75ff7398 ("Cygwin: open: Unlock fdtab before open_
> > > with_arch()") introduced a bug that fdtab lock was not unlocked when
> > > new fd cannot be allocated due to an error.
> > 
> > Worth restating how much this matters, because the leaked lock is not
> > fd-table-local. The dtable lock acquires and releases
> > `lock_process::locker`, a process-wide recursive muto that also guards
> > `fork`, exec/spawn, `dup`, and every `open` and `close`. So the
> > pre-fix code let the owning thread hold it forever, turning a
> > transient out-of-descriptors failure (`EMFILE`) into a permanent,
> > process-wide deadlock. That is why it is a showstopper even though the
> > trigger is rare.
> 
> I've neglected to add a h/t to Johannes for his series of analyses that have
> proven to me that often there is much more going on within Cygwin than meets
> the eye.  These comments are invaluable, every one.
> Thank you Johannes very much!

Thank you!!!
Johannes