Re: [patch 0/6] 3.14-rt1 fixes

[Nicholas Mc Guire <der.herr@hofr.at>]

On Fri, 02 May 2014, Mike Galbraith wrote:

> On Fri, 2014-05-02 at 15:39 +0400, Pavel Vasilyev wrote: 
> > 02.05.2014 15:12, Mike Galbraith ??????????:
> > > The following patches are fixes that fell out of testing rt1.  Patches
> > > 1-4 are intended to be folded into existing patches, 5-6 are
> > > replacements.
> > >
> > > fold:
> > > 1/6 - preempt-lazy-support.patch
> > > 2/6 - x86-preempt-lazy.patch
> > > 3/6 - hotplug-light-get-online-cpus.patch
> > > 4/6 - stomp-machine-raw-lock.patch
> > >
> > > replace:
> > > 5/6 - (prep)
> > > 6/6 - stomp-machine-deal-clever-with-stopper-lock.patch
> > >
> > > drop: (buggy - calls migrate_disable() _after_ maybe blocking)
> > > migrate_disable-pushd-down-in-atomic_dec_and_spin_lo.patch
> > 
> > 
Why would calling migrate_disable be buggy after blocking ?
at that point any per cpu data is not yet being accessed so its perfectly fine
to

  lock->block
   -> migrate 
    -> unblock->lock 
     -> migrate_disable on a new CPU
      -> access per_cpu object
     -> migrate_enable
  -> unlock

what problems would there be ?

thx!
hofrat