Messages in this thread | | | Date | Wed, 5 Jul 2017 20:50:23 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC v5 09/11] mm: Try spin lock in speculative path |
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On Fri, Jun 16, 2017 at 07:52:33PM +0200, Laurent Dufour wrote: > @@ -2294,8 +2295,19 @@ static bool pte_map_lock(struct vm_fault *vmf) > if (vma_has_changed(vmf->vma, vmf->sequence)) > goto out; > > - pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, > - vmf->address, &ptl); > + /* Same as pte_offset_map_lock() except that we call
comment style..
> + * spin_trylock() in place of spin_lock() to avoid race with > + * unmap path which may have the lock and wait for this CPU > + * to invalidate TLB but this CPU has irq disabled. > + * Since we are in a speculative patch, accept it could fail > + */ > + ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd); > + pte = pte_offset_map(vmf->pmd, vmf->address); > + if (unlikely(!spin_trylock(ptl))) { > + pte_unmap(pte); > + goto out; > + } > + > if (vma_has_changed(vmf->vma, vmf->sequence)) { > pte_unmap_unlock(pte, ptl); > goto out;
Right, so if you look at my earlier patches you'll see I did something quite disgusting here.
Not sure that wants repeating, but I cannot remember why I thought this deadlock didn't exist anymore.
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