Re: [patch V5 11/16] futex: Provide infrastructure to plug the non contended robust futex unlock race

[Peter Zijlstra]

On Tue, Jun 02, 2026 at 11:10:04AM +0200, Thomas Gleixner wrote:
> When the FUTEX_ROBUST_UNLOCK mechanism is used for unlocking (PI-)futexes,
> then the unlock sequence in user space looks like this:
> 
>   1)	robust_list_set_op_pending(mutex);
>   2)	robust_list_remove(mutex);
> 	
>   	lval = gettid();
>   3)	if (atomic_try_cmpxchg(&mutex->lock, lval, 0))
>   4)		robust_list_clear_op_pending();
>   	else
>   5)		sys_futex(OP | FUTEX_ROBUST_UNLOCK, ....);

Ah!, see, your uapi patch earlier called that FUTEX_UNLOCK_ROBUST.

I'll fix it all up if I don't fine real issues.