flash-kernel puts QNAP on its knees

[Luca De Feo <luca.defeo@polytechnique.edu>]

Hello,

I have Debian stretch running on a QNAP TS-412, and I am having
serious problems lately with updates.

When flash-kernel is triggered by update-initramfs, the ssh connection
becomes laggy. First time it happened, I was kicked out, and any
successive attempts to ssh failed with a "Broken pipe" immediately
after accepting the password.

The second time I was luckier: I got back into my shell, but the root
fs had been remounted read-only. The last output I have from
flash-kernel before being cut out is

    kirkwood-qnap: machine: QNAP TS419 family
    DTB: kirkwood-ts419-6281.dtb
    Installing kirkwood-ts419-6281.dtb into /boot/dtbs
/4.0.0-2-kirkwood/kirkwood-ts419-6281.dtb
    Taking backup of kirkwood-ts419-6281.dtb.
    Installing new kirkwood-ts419-6281.dtb.
    flash-kernel: installing version 4.0.0-2-kirkwood
    flash-kernel: appending
/usr/lib/linux-image-4.0.0-2-kirkwood/kirkwood-ts419-6281.dtb to
kernel
    Generating kernel u-boot image... done.
    Flashing kernel (using 2076902/2097152 bytes)... done.
    Flashing initramfs (using 4604898/9437184 bytes)...

The last lines in syslog before the ro remount are

    Aug  9 01:28:38 debian kernel: [  231.740207] ata4.00: exception
Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
    Aug  9 01:28:38 debian kernel: [  231.824648] ata4.00: failed
command: FLUSH CACHE EXT
    Aug  9 01:28:38 debian kernel: [  231.884124] ata4.00: cmd
ea/00:00:00:00:00/00:00:00:00:00/a0 tag 27
    Aug  9 01:28:38 debian kernel: [  231.884124]          res
40/00:00:00:00:00/00:00:00:00:00/00 Emask 0x4 (timeout)
    Aug  9 01:28:38 debian kernel: [  232.047750] ata4.00: status: { DRDY }
    Aug  9 01:28:38 debian kernel: [  232.091592] ata4: hard resetting link
    Aug  9 01:28:39 debian kernel: [  232.877725] ata4: SATA link up
3.0 Gbps (SStatus 123 SControl 300)
    Aug  9 01:28:45 debian kernel: [  238.110920] ata4.00: qc timeout (cmd 0xec)
    Aug  9 01:28:45 debian kernel: [  238.159972] ata4.00: failed to
IDENTIFY (I/O error, err_mask=0x4)
    Aug  9 01:28:45 debian kernel: [  238.232969] ata4.00:
revalidation failed (errno=-5)
    Aug  9 01:28:45 debian kernel: [  238.291407] ata4: hard resetting link
    Aug  9 01:28:45 debian kernel: [  239.017033] ata4: SATA link up
3.0 Gbps (SStatus 123 SControl 300)
    Aug  9 01:28:56 debian kernel: [  249.175319] ata4.00: qc timeout (cmd 0xec)
    Aug  9 01:28:56 debian kernel: [  249.224367] ata4.00: failed to
IDENTIFY (I/O error, err_mask=0x4)
    Aug  9 01:28:56 debian kernel: [  249.297361] ata4.00:
revalidation failed (errno=-5)
    Aug  9 01:28:56 debian kernel: [  249.355799] ata4: limiting SATA
link speed to 1.5 Gbps
    Aug  9 01:28:56 debian kernel: [  249.417357] ata4: hard resetting link
    Aug  9 01:28:57 debian kernel: [  250.581397] ata4: SATA link up
1.5 Gbps (SStatus 113 SControl 310)

ata4 is the disk that contains my root fs.

Rebooting restores the system to a normal state

Any help appreciated.

Thanks,
Luca