* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Mon, 2009-06-15 at 20:25 +0200, Ingo Molnar wrote: > > * Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > but ... look at the APIs i propose above. We dont need _any_ > > 'types'. > > > > That type enumeration is basically an open-coded allocator. If we do > > a _real_ allocator (a balanced stack of atomic kmaps) we dont need > > any of those indices, and all the potential for mismatch goes away > > as well - a stack nests trivially with IRQ and NMI and arbitrary > > other contexts. > > You want types because: > - they encode the intent, and can be verified > - they help keep track of the max nesting depth > > In the proposed implementation all type code basically falls away > no ! CONFIG_DEBUG_VM, but is kept around for robustness. But much of the fragility of the types (and their clumsiness - for example in highpte ops we have to know at which level of the pagetables we are, and use the right kind of index) is _precisely_ because we have the types ... Unbalanced unmaps will be detected under CONFIG_DEBUG_VM: kunmap uses 'page' as a parameter which is checked against the pte entry - they must match. I.e. it becomes a symmetric and expressive API: kaddr = kmap_atomic(page); ... kunmap_atomic(page); Hm? Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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