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Re: Race condition with Raspberry Pi 3 root on NFS



"Aaron B." <aaron%zadzmo.org@localhost> writes:

> On Sun, 30 Oct 2022 16:54:34 -0700
> Andy Ruhl <acruhl%gmail.com@localhost> wrote:
>
>> On Sun, Oct 30, 2022 at 2:18 PM Aaron B. <aaron%zadzmo.org@localhost> wrote:
>
>> There used to be a way to build a kernel with a hardcoded NFS root
>> option. I dug around in evbarm and aarch64 and didn't see something
>> familiar to me (from like 15 years ago when I was doing this).
>> 
>
> It's a good thought - I have an O-Droid C1+ still on 7.1.2 booting
> exactly that way.
>
> The issue, though, is that the mue0 simply isn't in the device tree -
> not yet. The kernel boots up, looks for mue0, doesn't find it, then
> drops to a prompt. A few seconds later the USB bus stabilizes and mue0
> attaches.
>
> I assume attempting to use a USB key or USB-to-SATA device as root
> would result in the same behavior.

I tried to use a USB SSD as root and also had trouble.

I think the fix is to somehow delay the looking-for-root part of the
kernel.  I think there is some sort of delay param in RPI boot, but it
may be necessary to have it within the kernel.

I don't know why this doesn't show up on other systems with root-on-usb
but maybe that just tends not to happen.

It should not be too hard to put in the equivalent of sleep(10) before
mounting root, or perhaps in the NFS mountroot path to not slow down
others.

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