* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > On Mon, 2009-06-15 at 20:42 +0200, Ingo Molnar wrote: > > * 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 ... > > How will you manage the max depth? if (++depth == MAX_DEPTH) { print_all_entries_and_nasty_warning(); /* hope we'll live long enough for the syslog to touch disk */ depth = 0; } unbalanced kmap is a bad bug - the easier we make it to catch, the better. The system wouldnt survive anyway. 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