Figures, updating to 4.16.11 seems to have fixed this, and another issue I didn't report yet
where shutdown -r wasn't rebooting.

I take this back, the issue is still present.
Apparently it happens somewhat after the initial boot messages,
seemingly a while after I log in.

Please find the first kernel that has the issue and the last kernel that does not have the issue. Bisect between those two kernels then report the results of the bisection upstream.

that might take some time, unfortunately.

What I can see on an equivalent system running lts not demonstrating the problem is the following:

4.14.41-1-lts$ sensors -u
k10temp-pci-00c3
Adapter: PCI adapter
temp1:
temp1_input: 61.750
temp1_max: 70.000
temp1_crit: 70.000
temp1_crit_hyst: 65.000

k10temp-pci-00cb
Adapter: PCI adapter
temp1:
temp1_input: 61.750
temp1_max: 70.000

4.14.41-1-lts$ paclog-pkglist |grep sensor
lm_sensors 3.4.0-2
qt5-sensors 5.10.1-1

============

4.16.11-1-ARCH$ sensors -u
jc42-i2c-0-19
Adapter: SMBus PIIX4 adapter at 0b00
temp1:
ERROR: Can't get value of subfeature temp1_input: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read

k10temp-pci-00cb
Adapter: PCI adapter
temp1:
temp1_input: 29.000
temp1_max: 70.000

fam15h_power-pci-00c4
Adapter: PCI adapter
power1:
power1_input: 88.484
power1_crit: 99.211

jc42-i2c-0-1f
Adapter: SMBus PIIX4 adapter at 0b00
temp1:
ERROR: Can't get value of subfeature temp1_input: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read

jc42-i2c-0-1b
Adapter: SMBus PIIX4 adapter at 0b00
temp1:
ERROR: Can't get value of subfeature temp1_input: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read

nouveau-pci-0100
Adapter: PCI adapter
GPU core:
in0_input: 0.912
in0_min: 0.800
in0_max: 1.187
temp1:
temp1_input: 45.000
temp1_max: 95.000
temp1_max_hyst: 3.000
temp1_crit: 105.000
temp1_crit_hyst: 5.000
temp1_emergency: 135.000
temp1_emergency_hyst: 5.000

k10temp-pci-00c3
Adapter: PCI adapter
temp1:
temp1_input: 29.250
temp1_max: 70.000
temp1_crit: 70.000
temp1_crit_hyst: 67.000

w83795g-i2c-0-2f
Adapter: SMBus PIIX4 adapter at 0b00
in0:
in0_input: 0.000
in0_min: 0.680
in0_max: 1.454
in0_alarm: 0.000
in0_beep: 0.000
in2:
in2_input: 0.000
in2_min: 1.120
in2_max: 1.654
in2_alarm: 0.000
in2_beep: 0.000
in6:
in6_input: 0.000
in6_min: 0.984
in6_max: 1.214
in6_alarm: 0.000
in6_beep: 0.000
in7:
in7_input: 0.000
in7_min: 1.616
in7_max: 1.990
in7_alarm: 0.000
in7_beep: 0.000
in8:
in8_input: 0.000
in8_min: 1.128
in8_max: 1.382
in8_alarm: 0.000
in8_beep: 0.000
in9:
in9_input: 0.000
in9_min: 1.632
in9_max: 1.998
in9_alarm: 0.000
in9_beep: 0.000
in10:
in10_input: 0.000
in10_min: 1.416
in10_max: 1.526
in10_alarm: 0.000
in10_beep: 0.000
in11:
in11_input: 0.000
in11_min: 1.080
in11_max: 1.326
in11_alarm: 0.000
in11_beep: 0.000
+3.3V:
in12_input: 0.000
in12_min: 2.964
in12_max: 3.630
in12_alarm: 0.000
in12_beep: 0.000
3VSB:
in13_input: 0.000
in13_min: 2.964
in13_max: 3.630
in13_alarm: 0.000
in13_beep: 0.000
Vbat:
in14_input: 0.000
in14_min: 2.700
in14_max: 3.630
in14_alarm: 0.000
in14_beep: 0.000
fan1:
fan1_input: 0.000
fan1_min: 712.000
fan1_alarm: 0.000
fan1_beep: 0.000
fan2:
fan2_input: 0.000
fan2_min: 712.000
fan2_alarm: 0.000
fan2_beep: 0.000
fan3:
fan3_input: 0.000
fan3_min: 715.000
fan3_alarm: 0.000
fan3_beep: 0.000
fan4:
fan4_input: 0.000
fan4_min: 715.000
fan4_alarm: 0.000
fan4_beep: 0.000
fan5:
fan5_input: 0.000
fan5_min: 712.000
fan5_alarm: 0.000
fan5_beep: 0.000
fan6:
fan6_input: 0.000
fan6_min: 712.000
fan6_alarm: 0.000
fan6_beep: 0.000
temp3:
temp3_input: 0.000
temp3_max: 127.000
temp3_max_hyst: 127.000
temp3_crit: 85.000
temp3_crit_hyst: 80.000
temp3_alarm: 0.000
temp3_type: 3.000
temp3_beep: 0.000
temp6:
temp6_input: 0.000
temp6_max: 127.000
temp6_max_hyst: 127.000
temp6_crit: 75.000
temp6_crit_hyst: 70.000
temp6_alarm: 0.000
temp6_type: 4.000
temp6_beep: 0.000
temp7:
temp7_input: 0.000
temp7_max: 65.000
temp7_max_hyst: 62.000
temp7_crit: 65.000
temp7_crit_hyst: 62.000
temp7_alarm: 0.000
temp7_type: 5.000
temp7_beep: 0.000
intrusion0:
intrusion0_alarm: 0.000
intrusion0_beep: 0.000
beep_enable:
beep_enable: 0.000

jc42-i2c-0-1d
Adapter: SMBus PIIX4 adapter at 0b00
temp1:
ERROR: Can't get value of subfeature temp1_input: Can't read
ERROR: Can't get value of subfeature temp1_max: Can't read
ERROR: Can't get value of subfeature temp1_max_hyst: Can't read
ERROR: Can't get value of subfeature temp1_min: Can't read
ERROR: Can't get value of subfeature temp1_crit: Can't read
ERROR: Can't get value of subfeature temp1_crit_hyst: Can't read
ERROR: Can't get value of subfeature temp1_max_alarm: Can't read
ERROR: Can't get value of subfeature temp1_min_alarm: Can't read
ERROR: Can't get value of subfeature temp1_crit_alarm: Can't read

4.16.11-1-ARCH$ paclog-pkglist |grep sensor
lib32-lm_sensors 3.4.0-1
lm_sensors 3.4.0-3
qt5-sensors 5.10.1-1

perhaps the regression is in lm_sensors or at least in its runtime [re]configuration.

I notice that the first error is the following after clean dmesg:

[ 151.184781] i2c i2c-0: SMBus Timeout!
[ 151.184798] i2c i2c-0: Failed reset at end of transaction (01)
[ 151.184804] w83795 0-002f: Failed to read from register 0x017, err -6
[ 151.184824] i2c i2c-0: Failed! (01)
[ 151.184827] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 151.184846] i2c i2c-0: Failed! (01)
[ 151.184849] w83795 0-002f: Failed to read from register 0x018, err -16
[ 151.184867] i2c i2c-0: Failed! (01)
...

after updating to 4.16.12-1-ARCH

I now see instead:
[ 29.310057] i2c i2c-0: Found w83795g rev. B at 0x2f
[ 29.450079] w83795 0-002f: hwmon_device_register() is deprecated. Please convert the driver to use hwmon_device_register_with_info().
and
$ dmesg|grep w83795
[ 29.310057] i2c i2c-0: Found w83795g rev. B at 0x2f
[ 29.450079] w83795 0-002f: hwmon_device_register() is deprecated. Please convert the driver to use hwmon_device_register_with_info().
[ 100.685340] w83795 0-002f: Failed to read from register 0x0b3, err -6
[ 119.333533] w83795 0-002f: Failed to read from register 0x026, err -6
[ 119.383538] w83795 0-002f: Failed to read from register 0x212, err -5
[ 119.403522] w83795 0-002f: Failed to read from register 0x214, err -5
[ 125.613754] w83795 0-002f: Failed to read from register 0x019, err -6
[ 125.633749] w83795 0-002f: Failed to read from register 0x01a, err -6
[ 125.653749] w83795 0-002f: Failed to read from register 0x01b, err -5
[ 125.663753] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.673750] w83795 0-002f: Failed to read from register 0x01c, err -5
[ 125.683762] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.693747] w83795 0-002f: Failed to read from register 0x01d, err -5
[ 125.703766] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.713750] w83795 0-002f: Failed to read from register 0x01e, err -5
[ 125.723778] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.733770] w83795 0-002f: Failed to read from register 0x02e, err -5
[ 125.743793] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.753783] w83795 0-002f: Failed to read from register 0x02f, err -5
[ 125.763779] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.773799] w83795 0-002f: Failed to read from register 0x030, err -5
[ 125.783745] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.793767] w83795 0-002f: Failed to read from register 0x031, err -5
[ 125.803786] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.813765] w83795 0-002f: Failed to read from register 0x032, err -5
[ 125.823752] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.833778] w83795 0-002f: Failed to read from register 0x033, err -5
[ 125.843761] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.853745] w83795 0-002f: Failed to read from register 0x021, err -5
[ 125.863745] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.873746] w83795 0-002f: Failed to read from register 0x022, err -5
[ 125.883747] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.893746] w83795 0-002f: Failed to read from register 0x023, err -5
[ 125.903744] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.913749] w83795 0-002f: Failed to read from register 0x024, err -5
[ 125.923771] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.933954] w83795 0-002f: Failed to read from register 0x01f, err -5
[ 125.943752] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.953793] w83795 0-002f: Failed to read from register 0x020, err -5
[ 125.963818] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.973751] w83795 0-002f: Failed to read from register 0x026, err -5
[ 125.983772] w83795 0-002f: Failed to read from register 0x03c, err -5
[ 125.993740] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.003770] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.013765] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.023760] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.033750] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.043763] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.053768] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.063778] w83795 0-002f: Failed to set bank to 2, err -5
[ 126.073766] w83795 0-002f: Failed to read from register 0x040, err -5
[ 126.083763] w83795 0-002f: Failed to read from register 0x046, err -5
[ 126.093784] w83795 0-002f: Failed to write to register 0x040, err -5
[ 126.103778] w83795 0-002f: Failed to read from register 0x041, err -5
[ 126.113804] w83795 0-002f: Failed to read from register 0x042, err -5
[ 126.123792] w83795 0-002f: Failed to read from register 0x043, err -5
[ 126.133773] w83795 0-002f: Failed to read from register 0x044, err -5
[ 126.143781] w83795 0-002f: Failed to read from register 0x045, err -5
[ 126.153779] w83795 0-002f: Failed to read from register 0x046, err -5


Then my log becomes flooded with:
[ 845.060288] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060306] i2c i2c-0: Failed! (01)
[ 845.060308] w83795 0-002f: Failed to read from register 0x032, err -16
[ 845.060326] i2c i2c-0: Failed! (01)
[ 845.060329] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060347] i2c i2c-0: Failed! (01)
[ 845.060349] w83795 0-002f: Failed to read from register 0x033, err -16
[ 845.060367] i2c i2c-0: Failed! (01)
[ 845.060369] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060387] i2c i2c-0: Failed! (01)
[ 845.060390] w83795 0-002f: Failed to read from register 0x021, err -16
[ 845.060407] i2c i2c-0: Failed! (01)
[ 845.060410] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060428] i2c i2c-0: Failed! (01)
[ 845.060430] w83795 0-002f: Failed to read from register 0x022, err -16
[ 845.060448] i2c i2c-0: Failed! (01)
[ 845.060450] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060468] i2c i2c-0: Failed! (01)
[ 845.060470] w83795 0-002f: Failed to read from register 0x023, err -16
[ 845.060488] i2c i2c-0: Failed! (01)
[ 845.060490] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060508] i2c i2c-0: Failed! (01)
[ 845.060511] w83795 0-002f: Failed to read from register 0x024, err -16
[ 845.060529] i2c i2c-0: Failed! (01)
[ 845.060531] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060549] i2c i2c-0: Failed! (01)
[ 845.060551] w83795 0-002f: Failed to read from register 0x01f, err -16
[ 845.060571] i2c i2c-0: Failed! (01)
[ 845.060574] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060592] i2c i2c-0: Failed! (01)
[ 845.060595] w83795 0-002f: Failed to read from register 0x020, err -16
[ 845.060612] i2c i2c-0: Failed! (01)
[ 845.060615] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060633] i2c i2c-0: Failed! (01)
[ 845.060635] w83795 0-002f: Failed to read from register 0x026, err -16
[ 845.060653] i2c i2c-0: Failed! (01)
[ 845.060655] w83795 0-002f: Failed to read from register 0x03c, err -16
[ 845.060676] i2c i2c-0: Failed! (01)
[ 845.060678] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060699] i2c i2c-0: Failed! (01)
[ 845.060702] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060722] i2c i2c-0: Failed! (01)
[ 845.060724] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060745] i2c i2c-0: Failed! (01)
[ 845.060747] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060768] i2c i2c-0: Failed! (01)
[ 845.060770] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060791] i2c i2c-0: Failed! (01)
[ 845.060793] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060814] i2c i2c-0: Failed! (01)
[ 845.060816] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060836] i2c i2c-0: Failed! (01)
[ 845.060838] w83795 0-002f: Failed to set bank to 2, err -16
[ 845.060857] i2c i2c-0: Failed! (01)
[ 845.060859] w83795 0-002f: Failed to read from register 0x040, err -16
[ 845.060877] i2c i2c-0: Failed! (01)
[ 845.060879] w83795 0-002f: Failed to read from register 0x046, err -16
[ 845.060900] i2c i2c-0: Failed! (01)
[ 845.060902] w83795 0-002f: Failed to write to register 0x040, err -16
[ 845.060920] i2c i2c-0: Failed! (01)
[ 845.060923] w83795 0-002f: Failed to read from register 0x041, err -16
[ 845.060941] i2c i2c-0: Failed! (01)
[ 845.060943] w83795 0-002f: Failed to read from register 0x042, err -16
[ 845.060961] i2c i2c-0: Failed! (01)
[ 845.060963] w83795 0-002f: Failed to read from register 0x043, err -16
[ 845.061012] i2c i2c-0: Failed! (01)
[ 845.061015] w83795 0-002f: Failed to read from register 0x044, err -16
[ 845.061034] i2c i2c-0: Failed! (01)
[ 845.061036] w83795 0-002f: Failed to read from register 0x045, err -16
[ 845.061054] i2c i2c-0: Failed! (01)
[ 845.061057] w83795 0-002f: Failed to read from register 0x046, err -16
[ 845.061104] i2c i2c-0: Failed! (01)
[ 845.061107] w83795 0-002f: Failed to write to register 0x040, err -16

In other words, seems to change a bit every upgrade now.

I'm somewhat amazed nobody else sees this on arch, perhaps I'm the only
lucky one with a supermicro AMD box...

what might be a more generic linux bug database which might find others experiencing this?

I don't believe I can easily(read:safely) downgrade with ZoL (using DKMS) to bisect as suggested...
Perhaps there are logging flags I could set in the appropriate kernel module(s) to help debug?
Luckily I have the other machine on LTS not demonstrating the problem so there are times when I can
do comparisons albeit a bit wider spaced than a

I cannot reproduce the issue. Is it still valid for you?

now under 5.16.11-arch1-1
with
lib32-lm_sensors 1:3.6.0.r41.g31d1f125-1
lm_sensors 1:3.6.0.r41.g31d1f125-1
qt5-sensors 5.15.2-2

can't say I've seen the problem for a long while (since 4.x?)