On Thu, 2015-08-13 at 19:51 +0800, Kevin Hao wrote: > I didn't find anything unusual. But I think we do need to order the > load/store of esel_next when acquire/release tcd lock. For acquire, > add a data dependency to order the loads of lock and esel_next. > For release, even there already have a "isync" here, but it doesn't > guarantee any memory access order. So we still need "lwsync" for > the two stores for lock and esel_next.
I was going to say that esel_next is just a hint and it doesn't really matter if we occasionally get the wrong value, unless it happens often enough to cause more performance degradation than the lwsync causes. However, with the A-008139 workaround we do need to read the same value from esel_next both times. It might be less costly to save/restore an additional register instead of lwsync, though. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
