Hi Johannes,
On 8/3/2026 12:36 PM, Johannes Schindelin wrote:
Hi Takashi,
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!
..mark
