Re: i915.ko WC writes are slow after ea8596bb2d8d379

From: Ingo Molnar
Date: Thu Nov 19 2015 - 03:16:12 EST



* Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:

> > > A bisection pointed to
> > >
> > > commit ea8596bb2d8d37957f3e92db9511c50801689180
> > > Author: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
> > > Date: Thu Jul 18 20:47:53 2013 +0900
> > >
> > > kprobes/x86: Remove unused text_poke_smp() and text_poke_smp_batch() functions
> > >
> > > of which the active ingredient was just
> > >
> > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > > index b32ebf9..f4001e0 100644
> > > --- a/arch/x86/Kconfig
> > > +++ b/arch/x86/Kconfig
> > > @@ -2334,7 +2334,6 @@ config HAVE_ATOMIC_IOMAP
> > >
> > > config HAVE_TEXT_POKE_SMP
> > > bool
> > > - select STOP_MACHINE if SMP

Ouch...

This is certainly an educative example of how pure 'code removal' patches can have
unintended side effects.

Is there a full fix patch available, and is anyone pushing that to Linus?

Thanks,

Ingo
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