On Wed, 2014-05-21 at 11:43 +0900, Hidetoshi Seto wrote: > (2014/05/21 11:03), Chen Yucong wrote: > > On Wed, 2014-05-21 at 10:40 +0900, Hidetoshi Seto wrote: > >> (2014/05/20 11:11), Chen Yucong wrote: > >>> mces_seen is a Per-CPU variable which should only be accessed by Per-CPU > >>> as possible. So the > >>> clear operation of mces_seen should also be lcoal to Per-CPU rather than > >>> monarch CPU. > >> > >> I don't think it should be local. > >> Originally what we want to have here is memory to save mces_seen for each > >> online cpus, > >> such as a global array like mces_seen[cpus]. But at same time we don't > >> want to preallocate > >> big array enough for max possible cpus. So we use per-cpu store instead. > >> > > But mces_seen will just be updated by Per-CPU rather than monarch CPU. > > It is only read by monarch CPU. > > Because mce status registers are per-cpu and monarch cannot access subjects' > registers > directly, Right. This is one reason why we need to distribute the clear operation to Per-CPU. And in fact it exactly assigns per-cpu property to mces_seen.
> all subjects read it's status for monarch, store the status to memory for > monarch, > and then monarch gather all status to make decision for all. mce_regin, which is only called by monarch CPU, can be used for system panics as quickly as possible if there is a truly data corrupting error. But Monarch CPU don't have to help all other CPU to clean mces_clean. One advantage of Per-CPU is the isolation of errors propagation, being so, why do not we clean mces_seen by Per-CPU? thx! cyc > > At last monarch kindly clear gathered status for all. > It will be one of important steps to ready for next mce events. > > I think you should clarify why "distributing the clear operation" is required > here. > What is the benefit? > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
