On Tue, 16 Oct 2018 20:42:07 +0200 Sebastian Andrzej Siewior <[email protected]> wrote:
> On 2018-10-16 11:01:14 [-0700], Stephen Hemminger wrote: > > On Tue, 16 Oct 2018 18:55:45 +0200 > > Sebastian Andrzej Siewior <[email protected]> wrote: > > > > > Also, ptr->var++ is not an atomic operation even on 64bit CPUs. Which > > > means if try_fill_recv() runs on CPU0 (via virtnet_receive()) then the > > > worker might run on CPU1. > > > > On modern CPU's increment of native types is atomic but not locked. > > u64_stats_update_begin is a no-op on UP and also if BIT_PER_LONG != 32 > > On ARM64 you have load, inc, store. So if two CPUs increment the counter > simultaneously we might lose one increment. That is why I asked if we > care or not. > > Sebastian The point is that kicks is just a counter, not important as part of the device operation. The point of the u64_stats is to avoid problems with high/low 32 bit wrap on increment. So this is ok on ARM64. _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
