PMON xcvrd crash with master image 498

[yxieca]

Description

Steps to reproduce the issue:

1. Nightly test

Describe the results you received:
PMON crash causing all test to fail sanity check

Describe the results you expected:
Run nightly test

Additional information you deem important (e.g. issue happens only occasionally):

**Output of `show version`:**

```

SONiC Software Version: SONiC.master.498-5fbb6ee6
Distribution: Debian 10.6
Kernel: 4.19.0-9-2-amd64
Build commit: 5fbb6ee
Build date: Fri Nov 20 14:36:29 UTC 2020
Built by: johnar@jenkins-worker-3
```

**Attach debug file `sudo generate_dump`:**

Nov 21 18:10:26.955052 str2-7050cx3-acs-07 ERR pmon#ledd[32]: :- initializeGlobalConfig: Sonic database config global file doesn't exist at /var/run/redis/sonic-db/database_global.json
Nov 21 18:10:29.024274 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd Traceback (most recent call last):
Nov 21 18:10:29.024274 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/bin/xcvrd", line 8, in <module>
Nov 21 18:10:29.024274 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     sys.exit(main())
Nov 21 18:10:29.024274 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/lib/python2.7/dist-packages/xcvrd/xcvrd.py", line 1318, in main
Nov 21 18:10:29.024738 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     xcvrd.run()
Nov 21 18:10:29.024801 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/lib/python2.7/dist-packages/xcvrd/xcvrd.py", line 1268, in run
Nov 21 18:10:29.024842 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     self.init()
Nov 21 18:10:29.024883 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/lib/python2.7/dist-packages/xcvrd/xcvrd.py", line 1241, in init
Nov 21 18:10:29.025171 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     y_cable_helper.init_ports_status_for_y_cable(platform_sfputil, platform_chassis, self.y_cable_presence, self.stop_event)
Nov 21 18:10:29.025324 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/lib/python2.7/dist-packages/xcvrd/xcvrd_utilities/y_cable_helper.py", line 295, in init_ports_status_for_y_cable
Nov 21 18:10:29.025324 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     state_db, port_tbl, y_cable_tbl, asic_index, logical_port_name, y_cable_presence)
Nov 21 18:10:29.025344 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/lib/python2.7/dist-packages/xcvrd/xcvrd_utilities/y_cable_helper.py", line 224, in check_identifier_presence_and_update_mux_table_entry
Nov 21 18:10:29.025344 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     logical_port_name, y_cable_tbl[asic_index])
Nov 21 18:10:29.025370 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/lib/python2.7/dist-packages/xcvrd/xcvrd_utilities/y_cable_helper.py", line 169, in update_statedb_port_mux_status_table
Nov 21 18:10:29.025370 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     read_side = y_cable.check_read_side(physical_port)
Nov 21 18:10:29.025386 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd   File "/usr/local/lib/python2.7/dist-packages/sonic_y_cable/y_cable.py", line 149, in check_read_side
Nov 21 18:10:29.025399 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd     regval_read = struct.unpack(">B", result)
Nov 21 18:10:29.025399 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd struct.error: 
Nov 21 18:10:29.025871 str2-7050cx3-acs-07 INFO pmon#supervisord: xcvrd unpack requires a string argument of length 1
Nov 21 18:10:30.078791 str2-7050cx3-acs-07 WARNING pmon#psud[35]: Power absence warning: psu1 is out of power.
Nov 21 18:10:30.103103 str2-7050cx3-acs-07 INFO pmon#supervisor-proc-exit-listener: Process xcvrd exited unxepectedly. Terminating supervisor...

[jleveque]

@vdahiya12: This seems to be related to your recent changes. Can you please investigate?

[vdahiya12]

the mux_cable tag seems to be introduced for non y_cable ports, this should not happen if the port is not on a Credo y_cable
admin@str2-7050cx3-acs-07:~$ redis-cli -n 4 hgetall "PORT|Ethernet112"

1. "index"
2. "29"
3. "lanes"
4. "117,118,119,120"
5. "fec"
6. "rs"
7. "admin_status"
8. "up"
9. "mtu"
10. "9100"
11. "alias"
12. "Ethernet29/1"
13. "pfc_asym"
14. "off"
15. "speed"
16. "100000"

17) "mux_cable"

18) "true"

19. "description"
20. "ARISTA01T1:Ethernet2"
    this PR should fix the crash however
    [sonic_y_cable] support for error handling non-expected eeprom_read return values inside sonic_y_cable sonic-platform-common#147

[yxieca]

image 502 still have the same crash

[yxieca]

The fix is not in 502. build 503 has the fix.