ubuntu_kernel_selftests ftrace fails on arm64 F / aws-5.8 / amd64 F azure-5.8

[Krzysztof Kozlowski]

[Impact]

arm64 only focal/aws 5.8.0-1031.33~20.04.1-aws and 5.8.0-1032.34~20.04.1-aws - regression. Works fine on previous Focal cycle (5.8.0-1028.30~20.04.3-aws) and current Groovy 5.8.

12. 05/06 07:01:39 DEBUG| utils:0153| [stdout] TAP version 13
13. 05/06 07:01:39 DEBUG| utils:0153| [stdout] 1..1
14. 05/06 07:01:39 DEBUG| utils:0153| [stdout] # selftests: ftrace: ftracetest
15. 05/06 07:01:39 DEBUG| utils:0153| [stdout] # === Ftrace unit tests ===
16. 05/06 07:01:39 DEBUG| utils:0153| [stdout] # [1] Basic trace file check [PASS]
17. 05/06 07:01:41 DEBUG| utils:0153| [stdout] # [2] Basic test for tracers [PASS]
18. 05/06 07:01:41 DEBUG| utils:0153| [stdout] # [3] Basic trace clock test [PASS]
19. 05/06 07:01:41 DEBUG| utils:0153| [stdout] # [4] Basic event tracing check [PASS]
20. 05/06 07:01:42 DEBUG| utils:0153| [stdout] # [5] Change the ringbuffer size [PASS]
21. 05/06 07:01:42 DEBUG| utils:0153| [stdout] # [6] Snapshot and tracing setting [PASS]
22. 05/06 07:01:42 DEBUG| utils:0153| [stdout] # [7] trace_pipe and trace_marker [PASS]
23. 05/06 07:01:42 DEBUG| utils:0153| [stdout] # [8] Test ftrace direct functions against tracers [UNRESOLVED]
24. 05/06 07:01:43 DEBUG| utils:0153| [stdout] # [9] Test ftrace direct functions against kprobes [UNRESOLVED]
25. 05/06 07:01:43 DEBUG| utils:0153| [stdout] # [10] Generic dynamic event - add/remove kprobe events [PASS]
26. 05/06 07:01:43 DEBUG| utils:0153| [stdout] # [11] Generic dynamic event - add/remove synthetic events [PASS]
27. 05/06 07:01:44 DEBUG| utils:0153| [stdout] # [12] Generic dynamic event - selective clear (compatibility) [PASS]
28. 05/06 07:01:44 DEBUG| utils:0153| [stdout] # [13] Generic dynamic event - generic clear event [PASS]
29. 05/06 07:01:44 DEBUG| utils:0153| [stdout] # [14] event tracing - enable/disable with event level files [PASS]
30. 05/06 07:01:45 DEBUG| utils:0153| [stdout] # [15] event tracing - restricts events based on pid notrace filtering [FAIL]
31. 05/06 07:01:45 DEBUG| utils:0153| [stdout] # [16] event tracing - restricts events based on pid [PASS]
32. 05/06 07:01:45 DEBUG| utils:0153| [stdout] # [17] event tracing - enable/disable with subsystem level files [PASS]
33. 05/06 07:01:46 DEBUG| utils:0153| [stdout] # [18] event tracing - enable/disable with top level files [PASS]

[Test Plan]

 * Run ftrace test from kernel selftests.

[Where problems could occur]

 * Only kernel selftests should be affected.
 * ftrace test can have false positives or negatives.

[Kelsey Steele (kelsey-steele)]

Found failing on two hosts for f/aws-5.8:

a1.medium (arm64) - passed on a retrigger, though when the test was ran again (rerun #4), ftracetest once again failed. Seems to be intermittent.

t2.small (amd64) - So far is consistently failing here. Didn't find to be failing on any other amd64 hosts.

[Kelsey Steele (kelsey-steele)]

Ian was able to get ftrace to pass on t2.small. It took a few tries, though at least shows that it is flaky there as well.

[Krzysztof Kozlowski (krzk)]

Found on focal/azure-5.8: 5.8.0-1033.35~20.04.1 and 5.8.0-1034.36~20.04.1 on Azure Standard_B1ms. Passes on other (bigger) instance types.

[Krzysztof Kozlowski (krzk)]

On Azure Standard_B1ms with focal/5.8.0-1033-azure reproduced only sometimes. Also sometimes similar failure appears with testcase [87] (not [15] as reported here):

[87] (instance) event tracing - restricts events based on pid notrace filtering [FAIL]

[Krzysztof Kozlowski (krzk)]

Sent patch upstream: https://lore.kernel<email address hidden>/T/#u
SRU needed for Focal+.

[Krzysztof Kozlowski (krzk)]

Fix accepted in mainline. Sent SRU.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-hirsute' to 'verification-done-hirsute'. If the problem still exists, change the tag 'verification-needed-hirsute' to 'verification-failed-hirsute'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal' to 'verification-done-focal'. If the problem still exists, change the tag 'verification-needed-focal' to 'verification-failed-focal'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!