Re: [PATCH v4 0/5] arm64: vdso: Implement __vdso_futex_robust_try_unlock()

[André Almeida]

Thomas!

Em 05/07/2026 17:23, Thomas Gleixner escreveu:
> On Sun, Jul 05 2026 at 14:56, André Almeida wrote:
> > As explained in the Testing section above, we developed a test that puts
> > breakpoints in the code to test if a user code being interrupted really clears
> > the op_pending pointer. This test wasn't initially working because of this check
> > at futex_fixup_robust_unlock():
> >
> >          /*
> >           * Avoid dereferencing current->mm if not returning from interrupt.
> >           * current->rseq.event is going to be used subsequently, so bringing the
> >           * cache line in is not a big deal.
> >           */
> >          if (!current->rseq.event.user_irq)
> > 		return;
> >
> > rseq.event.user_irq was always false during my tests, and it prevents the fixup
> > to happen. I figured out that arm64_syscall_enter_from_user_mode() was the
> > issue because it doesn't set user_irq to true when the task comes from a
> > syscall.
>
> I have no idea what you are babbling about.
>
> A syscall enter never sets user_irq to true. It's only set to true when
> an interrupt/exception entry comes from user space, i.e. via
>
>      irqentry_enter_from_user_mode()
>          rseq_note_user_irq_entry()

Sorry for the babbling, you are right. I got confused by analyzing the 
kernel stack trace after running the tests and wrongly thought that I 
spotted something missing. Please ignore patch 1/5.

> No?
>
> Thanks,
>
>          tglx