Re: [RFC][PATCH 4/6] arm, mm: Convert arm to generic tlb

[Peter Zijlstra]

On Thu, 2012-05-17 at 18:33 +0200, Peter Zijlstra wrote:
> On Thu, 2012-05-17 at 18:24 +0200, Peter Zijlstra wrote:
> > On Thu, 2012-05-17 at 17:00 +0100, Catalin Marinas wrote:
> > 
> > > BTW, looking at your tlb-unify branch, does tlb_remove_table() call
> > > tlb_flush/tlb_flush_mmu before freeing the tables?  I can only see
> > > tlb_remove_page() doing this. On ARM, even UP, we need the TLB flushing
> > > after clearing the pmd and before freeing the pte page table (and
> > > ideally doing it less often than at every pte_free_tlb() call).
> > 
> > No I don't think it does, so far the only archs using the RCU stuff are
> > ppc,sparc and s390 and none of those needed that (Xen might join them
> > soon though). But I will have to look and consider this more carefully.
> > I 'lost' most of the ppc/sparc/s390 details from memory to say this with
> > any certainty.
> 
> 
> Hmm, no, thinking more that does indeed sounds strange, I'll still have
> to consider it more carefully, but I think you might have found a bug
> there.

So the RCU code can from ppc in commit
267239116987d64850ad2037d8e0f3071dc3b5ce, which has similar behaviour.
Also I suspect the mm_users < 2 test will be incorrect for ARM since
even the one user can be concurrent with your speculation engine.


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