netdev - Re: [PATCH v2 1/2] net: make driver settling time configurable

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Message-ID: <ff6cef18-c1fb-4a1e-91a5-fb713086474e@davidv.dev>
Date: Thu, 8 Feb 2024 17:42:58 +0100
From: David <david@...idv.dev>
To: Denis Kirjanov <dkirjanov@...e.de>
Cc: Jonathan Corbet <corbet@....net>, "David S. Miller"
 <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Paul E. McKenney" <paulmck@...nel.org>, Randy Dunlap
 <rdunlap@...radead.org>, Xiongwei Song <xiongwei.song@...driver.com>,
 "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:NETWORKING [IPv4/IPv6]" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] net: make driver settling time configurable

On 2/8/24 11:26, Denis Kirjanov wrote:
>
> On 2/8/24 12:52, David Ventura wrote:
>> During IP auto configuration, some drivers apparently need to wait a
>> certain length of time to settle; as this is not true for all drivers,
>> make this length of time configurable.
>>
>> Signed-off-by: David Ventura <david@...idv.dev>
>> ---
>>   .../admin-guide/kernel-parameters.txt         |  4 ++++
>>   Documentation/admin-guide/nfs/nfsroot.rst     |  3 +++
>>   net/ipv4/ipconfig.c                           | 23 ++++++++++++++++---
>>   3 files changed, 27 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index b47940577c10..b07a035642fa 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -2291,6 +2291,10 @@
>>   
>>   	ip=		[IP_PNP]
>>   			See Documentation/admin-guide/nfs/nfsroot.rst.
>> +	ip.dev_wait_ms=
>> +			[IP_PNP]
>> +			See Documentation/admin-guide/nfs/nfsroot.rst.
>> +
>>   
>>   	ipcmni_extend	[KNL,EARLY] Extend the maximum number of unique System V
>>   			IPC identifiers from 32,768 to 16,777,216.
>> diff --git a/Documentation/admin-guide/nfs/nfsroot.rst b/Documentation/admin-guide/nfs/nfsroot.rst
>> index 135218f33394..f26f7a342af6 100644
>> --- a/Documentation/admin-guide/nfs/nfsroot.rst
>> +++ b/Documentation/admin-guide/nfs/nfsroot.rst
>> @@ -223,6 +223,9 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:<dns
>>     /proc/net/ipconfig/ntp_servers to an NTP client before mounting the real
>>     root filesystem if it is on NFS).
>>   
>> +ip.dev_wait_ms=<value>
>> +  Set the number of milliseconds to delay after opening the network device
>> +  which will be autoconfigured. Defaults to 10 milliseconds.
>>   
>>   nfsrootdebug
>>     This parameter enables debugging messages to appear in the kernel
>> diff --git a/net/ipv4/ipconfig.c b/net/ipv4/ipconfig.c
>> index c56b6fe6f0d7..cbf35163b973 100644
>> --- a/net/ipv4/ipconfig.c
>> +++ b/net/ipv4/ipconfig.c
>> @@ -82,8 +82,6 @@
>>   #define IPCONFIG_DYNAMIC
>>   #endif
>>   
>> -/* Define the friendly delay before and after opening net devices */
>> -#define CONF_POST_OPEN		10	/* After opening: 10 msecs */
>>   
>>   /* Define the timeout for waiting for a DHCP/BOOTP/RARP reply */
>>   #define CONF_OPEN_RETRIES 	2	/* (Re)open devices twice */
>> @@ -101,6 +99,7 @@
>>   
>>   /* Wait for carrier timeout default in seconds */
>>   static unsigned int carrier_timeout = 120;
>> +static unsigned int dev_wait_ms = 10;
>>   
>>   /*
>>    * Public IP configuration
>> @@ -1516,7 +1515,8 @@ static int __init ip_auto_config(void)
>>   		return err;
>>   
>>   	/* Give drivers a chance to settle */
>> -	msleep(CONF_POST_OPEN);
>> +	if(dev_wait_ms > 0)
>> +		msleep(dev_wait_ms);
> What's the point to wait more than CONF_POST_OPEN with the change?

I didn't have anything specificin mind - shall I change this

to only enable/disable the 10ms wait instead of allowing a configurable 
value?

>>   
>>   	/*
>>   	 * If the config information is insufficient (e.g., our IP address or
>> @@ -1849,3 +1849,20 @@ static int __init set_carrier_timeout(char *str)
>>   	return 1;
>>   }
>>   __setup("carrier_timeout=", set_carrier_timeout);
>> +
>> +
>> +static int __init set_dev_wait_ms(char *str)
>> +{
>> +	ssize_t ret;
>> +
>> +	if (!str)
>> +		return 0;
>> +
>> +	ret = kstrtouint(str, 0, &dev_wait_ms);
>> +	if (ret)
>> +		return 0;
>> +
>> +	return 1;
>> +}
>> +
>> +__setup("ip.dev_wait_ms=", set_dev_wait_ms);