Re: [tip: locking/urgent] futex: Allow to resize the private local hash

[Sebastian Andrzej Siewior]

On 2025-06-17 02:23:08 [-0700], Calvin Owens wrote:
> Ugh, I'm sorry, I was in too much of a hurry this morning... cargo is
> obviously not calling PR_FUTEX_HASH which is new in 6.16 :/
No worries.

> > This is with LTO enabled.
> 
> Full lto with llvm-20.1.7.
> 
…
> Nothing showed up in the logs but the RCU stalls on CPU16, always in
> queued_spin_lock_slowpath().
> 
> I'll run the build it was doing when it happened in a loop overnight and
> see if I can trigger it again.

Please check if you can reproduce it and if so if it also happens
without lto.
I have no idea why one spinlock_t remains locked. It is either locked or
some stray memory.

Oh. Lockdep adds quite some overhead but it should complain that a
spinlock_t is still locked while returning to userland.

> > > Thanks,
> > > Calvin
> > 
Sebastian