Re: [PATCH resend] fs/proc: Move kfree outside pde_unload_lock

[Nathan Zimmer <nzimmer@sgi.com>]

On 04/04/2013 11:11 AM, Al Viro wrote:
> On Thu, Apr 04, 2013 at 10:53:39AM -0500, Nathan Zimmer wrote:
>> This moves a kfree outside a spinlock to help scaling on larger (512 core)
>> systems.  This should be some relief until we can move the section to use
>> the rcu.
> Umm...  That'll get wrecked as soon as fixes from #experimental go in;
> FWIW, I'd probably make close_pdeo() return pdeo or NULL, depending on
> whether we want it freed.  With kfree() itself taken to callers.
> But there's much bigger fish to fry there - turn use_pde() into
> return atomic_inc_unless_negative(&pde->pde_users), unuse_pde() into
> if (atomic_dec_return(&pde->pde_users) == BIAS) complete(pde->....)
> and make sure entry_rundown() sets completion *before* adding BIAS
> to pde_users and waits for it only if the sum was equal to BIAS.
> The spinlock is still needed, but only on the "now taking care of
> any pdeo that might still be around" side of things - it protects
> pdeo list.
>
> Again, see the last two commits of vfs.git#experimental.  I'd certainly
> appreciate any extra eyes on that sucker...
Ok I am cloning the tree now.
It does look like the patches would conflict.
I'll run some tests and take a deeper look.