Re: [PATCH 1/2] powerpc: export thread-tidr interfaces

[Sukadev Bhattiprolu]

Frederic Barrat [fbarrat@xxxxxxxxxxxxxxxxxx] wrote:
> Hi,
> 
> 
> > diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
> > index 2010e4c..f20c1ad 100644
> > --- a/arch/powerpc/kernel/process.c
> > +++ b/arch/powerpc/kernel/process.c
> > @@ -1560,6 +1560,7 @@ void clear_thread_tidr(struct task_struct *t)
> >   	free_thread_tidr(t->thread.tidr);
> >   	t->thread.tidr = 0;
> >   }
> > +EXPORT_SYMBOL_GPL(clear_thread_tidr);
> 
> Isn't it dangerous to export clear_thread_tidr()? Other modules may also
> have assigned the TIDR by calling set_thread_tidr(), so clearing it could
> potentially break those other modules. My understanding is that once the
> TIDR is assigned, there's no safe way to reclaim it other than the thread
> exiting. Or we would need some kind of reference counter.

Yes the FTW driver avoids calling clear_thread_tidr() for the same reasons.
I don't have a strong case for exporting clear_thread_tidr(). Here is the
updated patch, exporting just the set_thread_tidr().

Thanks,

Sukadev
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