From: David Laight <David.Laight@ACULAB.COM>
To: 'Eric Dumazet' <eric.dumazet@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: netdev <netdev@vger.kernel.org>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
Eric Dumazet <edumazet@google.com>
Subject: RE: [PATCH net-next 1/9] vlan: adopt u64_stats_t
Date: Wed, 8 Jun 2022 10:18:22 +0000 [thread overview]
Message-ID: <cea2c2c39d0e4f27b2e75cdbc8fce09d@AcuMS.aculab.com> (raw)
In-Reply-To: <20220607233614.1133902-2-eric.dumazet@gmail.com>
From: Eric Dumazet
> Sent: 08 June 2022 00:36
>
> As explained in commit 316580b69d0a ("u64_stats: provide u64_stats_t type")
> we should use u64_stats_t and related accessors to avoid load/store tearing.
>
> Add READ_ONCE() when reading rx_errors & tx_dropped.
Isn't this all getting entirely stupid?
AFAICT nearly every 'memory' access in the kernel is going
to get wrapped in READ/WRITE_ONCE() to avoid something
that really never actually happens?
It might be better to just mark everything 'volatile'.
Although perhaps that ought to be a compiler option.
OTOH I've seen gcc generate extra instructions for 'volatile'
accesses - to the point where I used 'barrier()' to optimise
code.
I think the volatile casts in READ_ONCE() can generate worse
code than volatile variables.
David
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Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-06-08 10:30 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-07 23:36 [PATCH net-next 0/9] net: Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 1/9] vlan: adopt u64_stats_t Eric Dumazet
2022-06-08 10:18 ` David Laight [this message]
2022-06-08 10:37 ` Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 2/9] ipvlan: " Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 3/9] sit: use dev_sw_netstats_rx_add() Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 4/9] ip6_tunnel: " Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 5/9] wireguard: " Eric Dumazet
2022-06-08 7:36 ` Jason A. Donenfeld
2022-06-08 15:41 ` Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 6/9] net: adopt u64_stats_t in struct pcpu_sw_netstats Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 7/9] devlink: adopt u64_stats_t Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 8/9] drop_monitor: " Eric Dumazet
2022-06-07 23:36 ` [PATCH net-next 9/9] team: " Eric Dumazet
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