Re: [PATCH net-next v2 4/7] net: openvswitch: fix load tearing with u64_stats

[Eric Dumazet]

On Mon, Jan 26, 2026 at 7:29 PM David Laight
<david.laight.linux@xxxxxxxxx> wrote:
>
> On Sat, 24 Jan 2026 00:21:36 +0800
> David Yang <mmyangfl@xxxxxxxxx> wrote:
>
> > On 64bit arches, struct u64_stats_sync is empty and provides no help
> > against load/store tearing. struct copying should not be considered
> > tear-free. Use u64_stats_reads() instead.
>
> Except that the compiler doesn't ever generate 'tearing accesses' for
> aligned 64bit accesses on any 64bit architecture.
> Similarly memcpy() won't generate problematic accesses.
>
> The problem is purely theoretical - the C language lets the compiler
> split accesses, but it doesn't.

Yeah, although we still have races that KCSAN can detect.

data_race() or READ_ONCE() would be necessary to avoid noisy KCSAN reports.

While many LCSAN reports are boring, some of them point to real bugs.