Re: [RFC PATCH] futex: Remove requirement for lock_page in get_futex_key

[Sebastian Andrzej Siewior <sebastian@breakpoint.cc>]

On 2014-02-11 16:51:55 [+0100], Thomas Gleixner wrote:
> On Wed, 30 Oct 2013, Mel Gorman wrote:
> > On Wed, Oct 30, 2013 at 09:45:31AM +0100, Thomas Gleixner wrote:
> > > On Tue, 29 Oct 2013, Mel Gorman wrote:
> > > > Patch boots and futextest did not explode but I did no comparison
> > > > performance tests. Thomas, do you have details of the workload that
> > > > drove you to examine this problem? Alternatively, can you test it and
> > > The scenario is simple. All you need is a PSHARED futex.
> > > 
> > > Task A 
> > >      get_futex_key()
> > >      lock_page()
> > > 
> > > ---> preemption
> > > 
> > Do please. I'd rather not sink time into trying to reproduce a hypothetical
> > problem when people who are already familiar with it can provide better
> Took some time, but the folks finally came around to give it a try and
> it fixes their problem. I did not explode either, but I doubt, that
> their workload can trigger any of the corner cases.

I just stumbled uppon this patch and now I am curious about its status.
tglx said that it solves the problem in question (with doubt of
triggering all the corner cases). Chris pointed out that moving
put_page() might be worth doing.

Sebastian