> Execution is resumed exactly where it has been interrupted. > > > The idea behind my patch was to get rid of that nr_free_contexts counter > > that is (I thing) redundant with the context_map. > > Apparently its there to avoid the spinlock exactly on !FEW_CONTEXTS machines. > > I suppose that what happens is that get_mmu_context() gets preempted after > stealing > a context (so nr_free_contexts = 0), but before setting next_mmu_context to > the > next entry > > next_mmu_context = (ctx + 1) & LAST_CONTEXT;
Ugh ? Can switch_mm() be preempted at all ? Did I miss yet another "let's open 10 gazillion races for gun" Ingo patch ? > So if the now running higher prio tasks calls switch_mm() (which is likely to > happen) > it loops forever on atomic_dec_if_positive(&nr_free_contexts), while > steal_context() > sees "mm->context == CONTEXT". I think the race is only when destroy_context() is preempted, but maybe I missed something. > I think that you should try "preempt_disable()/preempt_enable" pair at entry > and > exit of get_mmu_context() - I suppose around destroy_context() is not enough > (you > can try that also). > > spinlock ends up calling preempt_disable().
