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    SubjectRe: PowerPC BUG: using smp_processor_id() in preemptible code
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    On Thu, 2011-02-24 at 12:47 -0800, Hugh Dickins wrote:

    > Reading back, I see Jeremy suggested moving vb_free()'s call to
    > vunmap_page_range() back inside vb->lock: it certainly was his moving
    > the call out from under that lock that brought the issue to my notice;
    > but it looked as if there were other paths which would give preemptible
    > PowerPC the same issue, just paths I happen not to go down myself. I'm
    > not sure, I didn't take the time to follow it up properly, expecting
    > further insight to arrive shortly from Ben!

    Yeah, sorry, I've been too over extended lately...

    > And, as threatened, Jeremy has further vmalloc changes queued up in
    > mmotm, which certainly make the patch below inadequate, and I imagine
    > the vunmap_page_range() movement too. I'm currently (well, I think most
    > recent mmotm doesn't even boot on my ppc) having to disable preemption
    > in the kernel case of apply_to_pte_range().
    >
    > What would be better for 2.6.38 and 2.6.37-stable? Moving that call to
    > vunmap_page_range back under vb->lock, or the partial-Peter-patch below?
    > And then what should be done for 2.6.39?

    Patch is fine. I should send it to Linus. It's not like we have a batch
    on the vmalloc space anyways since it doesnt do the arch_lazy_mmu stuff,
    so it's really about protecting the per-cpu variable.

    Cheers,
    Ben.

    > --- 2.6.38-rc5/arch/powerpc/mm/tlb_hash64.c 2010-02-24 10:52:17.000000000 -0800
    > +++ linux/arch/powerpc/mm/tlb_hash64.c 2011-02-15 23:27:21.000000000 -0800
    > @@ -38,13 +38,11 @@ DEFINE_PER_CPU(struct ppc64_tlb_batch, p
    > * neesd to be flushed. This function will either perform the flush
    > * immediately or will batch it up if the current CPU has an active
    > * batch on it.
    > - *
    > - * Must be called from within some kind of spinlock/non-preempt region...
    > */
    > void hpte_need_flush(struct mm_struct *mm, unsigned long addr,
    > pte_t *ptep, unsigned long pte, int huge)
    > {
    > - struct ppc64_tlb_batch *batch = &__get_cpu_var(ppc64_tlb_batch);
    > + struct ppc64_tlb_batch *batch = &get_cpu_var(ppc64_tlb_batch);
    > unsigned long vsid, vaddr;
    > unsigned int psize;
    > int ssize;
    > @@ -99,6 +97,7 @@ void hpte_need_flush(struct mm_struct *m
    > */
    > if (!batch->active) {
    > flush_hash_page(vaddr, rpte, psize, ssize, 0);
    > + put_cpu_var(ppc64_tlb_batch);
    > return;
    > }
    >
    > @@ -127,6 +126,7 @@ void hpte_need_flush(struct mm_struct *m
    > batch->index = ++i;
    > if (i >= PPC64_TLB_BATCH_NR)
    > __flush_tlb_pending(batch);
    > + put_cpu_var(ppc64_tlb_batch);
    > }
    >
    > /*
    > --
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