Re: [patch 5/8] futex: Add robust futex unlock IP range

[Mathieu Desnoyers]

On 2026-03-16 13:13, Thomas Gleixner wrote:
> There will be a VDSO function to unlock robust futexes in user space. The
> unlock sequence is racy vs. clearing the list_pending_op pointer in the
> tasks robust list head. To plug this race the kernel needs to know the
> instruction window. As the VDSO is per MM the addresses are stored in
> mm_struct::futex.
>
> Architectures which implement support for this have to update these
> addresses when the VDSO is (re)mapped.
>
> Arguably this could be resolved by chasing mm->context->vdso->image, but
> that that's architecture specific and requires to touch quite some cache
> lines. Having it in mm::futex reduces the cache line impact and avoids
> having yet another set of architecture specific functionality.
>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com