Re: [PATCH 0/2] finx argv_split() vs sysctl race

[Oleg Nesterov]

On 03/16, Andi Kleen wrote:
>
> > Perhaps rcu can be better, although a global rwsem looks simpler,
> > I dunno.
>
> It's a general problem with lots of sysctls.
> >
> > But argv_split() or its usage should be changed anyway, and GFP_KERNEL
> > won't work under rcu_read_lock().
>
> rcu strings has a helper function to copy the string for sleepy cases.

Then you need to pre-allocate, take rcu_read_lock(), copy, and check
that it actually fits the pre-allocated buffer. Not sure why the simple
rwsem is worse.

But I won't argue in any case

> > To me 1/2 looks as a simplification anyway, but I won't argue if we
> > decide to add rcu/locking and avoid this patch.
>
> Ok I'll revisit.

OK, but do you agree with 1/2?

Once again, this is subjective of course but imho this patch could be
considered as a cleanup/microoptimization, and it won't affect the rcu
changes.

Oleg.

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