netdev - Re: Commit "ipconfig wait for carrier" makes boot hang for 2 mins if no carrier

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Message-ID: <OF70CDBF7F.EFE301C2-ONC1257A70.002F0D3F-C1257A70.003055BF@transmode.se>
Date:	Wed, 5 Sep 2012 10:47:56 +0200
From:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
To:	Micha Nelissen <micha@...i.hopto.org>
Cc:	netdev@...r.kernel.org
Subject: Re: Commit "ipconfig wait for carrier" makes boot hang for 2 mins if no
   carrier



Micha Nelissen <micha@...i.hopto.org> wrote on 2012/09/05 10:30:36:

> From: Micha Nelissen <micha@...i.hopto.org>
> To: Joakim Tjernlund <joakim.tjernlund@...nsmode.se>,
> Cc: netdev@...r.kernel.org
> Date: 2012/09/05 10:30
> Subject: Re: Commit "ipconfig wait for carrier" makes boot hang for 2 mins if no   carrier
>
> Op 2012-09-05 9:04, Joakim Tjernlund schreef:
> >> Because that's where my root filesystem is? The IP autoconfiguration
> >> code exists for this purpose.
> >
> > This is not the only purpose.
>
> Documentation/filesystems/nfs/nfsroot.txt seems to suggest so (this is
> where the ip= parameter is documented), but it works independently indeed.
>
> So explain your reasons?
If you read that doc you find:

ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>

  This parameter tells the kernel how to configure IP addresses of devices
  and also how to set up the IP routing table. It was originally called
  `nfsaddrs', but now the boot-time IP configuration works independently of
  NFS, so it was renamed to `ip' and the old name remained as an alias for
  compatibility reasons.

>
> >>> The answer is probably the same, it is much easier to
> >>> manage our IP config in one place for our embedded system.
> >>
> >> You retrieve the kernel via TFTP or so when booting?
> >
> > Yes, but mostly not. This really doesn't matter
>
> Seems to me that if you boot standalone there is no reason to let the IP
> address be configured by the kernel? Retrieve the IP address in user
> space from your bootloader environment or whatever. And if you boot from
> ethernet (or some other networking interface), then you have a carrier,
> and there is no 2 minute delay (maybe less even than before with this
> patch!).

Everything is possible but we choosed to use already built-in functionality, as
did you.
You could have added an initram FS and done your NFS mount there so this
argument goes nowhere.

>
> >>> The wait should be conditional on NFS root or not so that non NFS roots
> >>> can skip this stage altogether.
> >
> > Your patch broke other use cases so my patch would just revert or change the tmo
> > to 2 secs or so.
> > Or you could clean up your stuff so it works for all and not just for you.
>
> It didn't break anything, it does work for you also, you just need to
> wait somewhat longer. Or make sure there is a carrier. The intent of the
> original 1 second delay was to let the link come up!

Sure it did, our system(and not only ours I bet) can not accept a 2 minute delay in
booting up the system for no reason.

Please adjust the 2 min wait to nfsroot= only and keep the old way for ip=

 Jocke

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