Re: [RFC] NUMA futex hashing

From: Andi Kleen
Date: Tue Aug 08 2006 - 08:47:53 EST

On Tuesday 08 August 2006 14:29, Eric Dumazet wrote:
> On Tuesday 08 August 2006 12:36, Andi Kleen wrote:
> > > We may have special case for PRIVATE futexes (they dont need to be
> > > chained in a global table, but a process private table)
> >
> > What do you mean with PRIVATE futex?
> >
> > Even if the futex mapping is only visible by a single MM mmap_sem is still
> > needed to protect against other threads doing mmap.
> Hum... I would call that a user error.
> If a thread is munmap()ing the vma that contains active futexes, result is
> undefined.

We can't allow anything that could crash the kernel, corrupt a kernel,
data structure, allow writing to freed memory etc. No matter how
defined it is or not. Working with a vma that doesn't have
an existence guarantee would be just that.

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