* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > The problem is the intrinsic utility of work_on_cpu(): we _really_ > > want such a generic facility to be usable from any (blockable) > > context, just like on_each_cpu(func, info) does for atomic functions, > > without restrictions on locking context. > > Do we? work_on_cpu() is some last-gasp oh-i-screwed-my-code-up thing. > We _really_ want people to use on_each_cpu()! why? on_each_cpu() is limited and runs in IRQ context. Is there a requirement that worklets need to be atomic? > We should bust a gut to keep the number of callers to the > resource-intensive (deadlocky!) work_on_cpu() to a minimum. i wouldnt call +10K 'resource intensive'. > (And to think that adding add_timer_on() creeped me out). > > hm. None of that was very helpful. How to move forward? > > I think I disagree that work_on_cpu() should be made into some robust, > smiled-upon core kernel facility. It _is_ slow, it _is_ deadlockable. uhm, why is it slow? It could be faster in fact in some cases: the main overhead in on_each_cpu() is having to wait for the IPIs - with a thread based approach if the other CPUs are idle we can get an IPI-less wakeup. > It should be positioned as something which is only used as a last > resort. And if you _have_ to use it, sort out your locking! > > Plus the number of code sites which want to fiddle with other CPUs in > this manner will always be small. cpufreq, MCE, irq-affinity, things > like that. > > What is the deadlock in acpi-cpufreq? Which lock, and who is the > "other" holder of that lock? a quick look suggests that it's dbs_mutex. Ingo -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
