Comment 4 for bug 1900728

I too cannot boot the linux-image-5.4.0-52-lowlatency kernel , here's the last couple of lines before a hang

- Unstable clock detected, switching default tracing clock to "global"
- If you want to keep using the local clock, then add :
     "trace_clock=local"
- on the kernel command line
- random: fast init done
- random: crng init done

After reverting back to linux-image-5.4.0-51-lowlatency kernel, here are the lines around those "random" lines

dmesg | grep -C 1 random
[ 0.556570] Memory: 32820996K/33548288K available (14339K kernel code, 2402K rwdata, 4964K rodata, 2648K init, 5056K bss, 727292K reserved, 0K cma-reserved)
[ 0.556583] random: get_random_u64 called from kmem_cache_open+0x2d/0x410 with crng_init=0
[ 0.556826] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=8, Nodes=1
--
[ 1.543599] scsi 0:0:0:0: CD-ROM PIONEER DVD-RW DVR-109 1.17 PQ: 0 ANSI: 5
[ 1.588068] random: fast init done
[ 1.602701] sr 0:0:0:0: [sr0] scsi3-mmc drive: 40x/40x writer cd/rw xa/form2 cdda tray
--
[ 1.644831] Run /init as init process
[ 1.665648] random: systemd-udevd: uninitialized urandom read (16 bytes read)
[ 1.666883] random: systemd-udevd: uninitialized urandom read (16 bytes read)
[ 1.666953] random: systemd-udevd: uninitialized urandom read (16 bytes read)
[ 1.693102] usb 1-1: new full-speed USB device number 2 using uhci_hcd
--
[ 4.010375] sd 2:0:0:0: [sdb] Attached SCSI disk
[ 5.084547] random: crng init done
[ 5.084609] random: 7 urandom warning(s) missed due to ratelimiting
[ 6.083105] ata4: SATA link down (SStatus 0 SControl 0)

---------------------

I'm thinking this is an issue with random number generation

This is an older machine with no TPM chip or random number generation support in the CPU, here's the first cpu's info

cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 23
model name : Intel(R) Xeon(R) CPU E5420 @ 2.50GHz
stepping : 10
microcode : 0xa0b
cpu MHz : 1994.962
cache size : 6144 KB
physical id : 0
siblings : 4
core id : 0
cpu cores : 4
apicid : 0
initial apicid : 0
fpu : yes
fpu_exception : yes
cpuid level : 13
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 xsave lahf_lm pti tpr_shadow vnmi flexpriority dtherm
bugs : cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit
bogomips : 4987.45
clflush size : 64
cache_alignment : 64
address sizes : 38 bits physical, 48 bits virtual
power management: