From: David Laight <David.Laight@ACULAB.COM>
To: 'Breno Leitao' <leitao@debian.org>,
"kuba@kernel.org" <kuba@kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Cc: "leit@fb.com" <leit@fb.com>,
"davem@davemloft.net" <davem@davemloft.net>,
"edumazet@google.com" <edumazet@google.com>,
"pabeni@redhat.com" <pabeni@redhat.com>,
"andrew@lunn.ch" <andrew@lunn.ch>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Michael van der Westhuizen" <rmikey@meta.com>
Subject: RE: [PATCH v3] netpoll: Remove 4s sleep during carrier detection
Date: Thu, 26 Jan 2023 09:04:42 +0000 [thread overview]
Message-ID: <6d13242627e84bde8129e75b6324d905@AcuMS.aculab.com> (raw)
In-Reply-To: <20230125185230.3574681-1-leitao@debian.org>
From: Breno Leitao
> Sent: 25 January 2023 18:53
> This patch removes the msleep(4s) during netpoll_setup() if the carrier
> appears instantly.
>
> Here are some scenarios where this workaround is counter-productive in
> modern ages:
>
> Servers which have BMC communicating over NC-SI via the same NIC as gets
> used for netconsole. BMC will keep the PHY up, hence the carrier
> appearing instantly.
>
> The link is fibre, SERDES getting sync could happen within 0.1Hz, and
> the carrier also appears instantly.
>
> Other than that, if a driver is reporting instant carrier and then
> losing it, this is probably a driver bug.
I can't help feeling that this will break something.
The 4 second delay does look counter productive though.
Obvious alternatives are 'wait a bit before the first check'
and 'require carrier to be present for a few checks'.
It also has to be said that checking every ms seems over enthusiastic.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2023-01-26 9:05 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 18:52 [PATCH v3] netpoll: Remove 4s sleep during carrier detection Breno Leitao
2023-01-26 9:04 ` David Laight [this message]
2023-01-26 10:52 ` Breno Leitao
2023-01-26 13:22 ` Andrew Lunn
2023-01-28 8:40 ` patchwork-bot+netdevbpf
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