From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [RFC] virtio_net: add local_bh_disable() around
 u64_stats_update_begin
Date: Tue, 16 Oct 2018 11:01:14 -0700
Message-ID: <20181016110114.73e2b248@xeon-e3>
References: <20181016165545.guksrl23ulcudxrk@linutronix.de>
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        tglx@linutronix.de,
        Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
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To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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On Tue, 16 Oct 2018 18:55:45 +0200
Sebastian Andrzej Siewior <bigeasy@linutronix.de> 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