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SubjectRe: [PATCH v2 03/36] mm: use do_futex() instead of sys_futex() in mm_release()
On Thu, Mar 15, 2018 at 08:04:56PM +0100, Dominik Brodowski wrote:
> sys_futex() is a wrapper to do_futex() which does not modify any
> values here:
>
> - uaddr, val and val3 are kept the same
>
> - op is masked with FUTEX_CMD_MASK, but is always set to FUTEX_WAKE.
> Therefore, val2 is always 0.
>
> - as utime is set to NULL, *timeout is NULL
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Darren Hart <dvhart@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>

Hi Dominik,

I'm missing the "why" part here. What is it you are trying to address?

do_futex is not currently in use outside of the futex implementation,
while sys_futex is. This decouples the interface from the
implementation. While this is perhaps less critical within the
kernel, I don't see a compelling reason to increase the coupling
between the mm and futex implementations.

Without a compelling WHY, Nack from me.

--
Darren Hart
VMware Open Source Technology Center

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