Re: Cannot boot with rootfs from eMMC if maxcpus=1

From: Randy Dunlap
Date: Sat Nov 18 2017 - 13:45:09 EST

On 11/09/2017 08:14 AM, Richard Schmitt wrote:
> Using a 4.9 kernel, trying to boot a kernel using an eMMC based rootfs will result in a crash
> The message preceeding the crash is:
> [ 3.285566] VFS: Cannot open root device "mmcblk0p9" or unknown-block(0,0): error -6
> [ 3.293338] Please append a correct "root=" boot option; here are the available partitions:
> Our kernel boot args can be seen in the boot log but for easy reference are:
> root=/dev/mmcblk0p9 earlycon clk_ignore_unused DEBUG_MODE=y siq_board_type=RP maxcpus=1
> Note that we do specify root=/dev/mmcblk0p9. If I simply remove maxcpus=1 from the kernel boot args, the system will boot up fine.
> Seems like there might be a race in bringing up the eMMC partitions prior to mounting the rootfs but I donât want to hypothesis any further.
> Any ideas?

If you suspect a timing issue, an easy test would be to add to the kernel
boot/command line either:
(in seconds) to see if that helps.

or send email to linux-arm-kernel@xxxxxxxxxxxxxxxxxxx ...