Comment 0 for bug 1882213

Copying a large file using cp on my Raspberry Pi 3B (not 3B+) from an externally-powered USB hard disk (Seagate Expansion 2TB) to an NFS-mounted filesystem across Ethernet causes the kernel of releases 19.10 and 20.04 to hang/freeze.

This happens every time the copy is attempted, although the exact duration from the start of the copy to the hang varies from a few seconds to a couple of minutes. The kernel does not recover even after long waits (30mins+), and a power reset (pulling the plug) is required. (Although I admit I haven't tried yet simply disconnecting the USB cable of the HDD during a hang.)

Likewise, messages are erratic and I suspect are only symptoms, notably watchdog BUG soft lockup messages and RCU stall messages on different CPU cores for different processes/threads. There are no hardware messages that I've seen recorded in log files (or appearing on the console) matching the incidents.

Although I have had a swapfile configured on the SD card, the hang continues to happen doing the cp after "swapoff -a". I've also tried playing with taskset affinities and snappiness to no obvious effect - the hangs still keep happening.

Copying from the external HDD to the SD card is successful, as is copying from the SD card to the NFS.

Raspbian 4.19.0-8 (armmp-lpae) does not have this problem; it successfully copies the file from HDD to NFS across Ethernet without stalling.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.4.0-1011-raspi 5.4.0-1011.11
ProcVersionSignature: Ubuntu 5.4.0-1011.11-raspi 5.4.34
Uname: Linux 5.4.0-1011-raspi aarch64
ApportVersion: 2.20.11-0ubuntu27
Architecture: arm64
CasperMD5CheckResult: skip
Date: Fri Jun 5 07:37:44 2020
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=C.UTF-8
 SHELL=/bin/bash
SourcePackage: linux-raspi
UpgradeStatus: Upgraded to focal on 2020-05-21 (14 days ago)