search

nasa / osal

The Core Flight System (cFS) Operating System Abstraction Layer (OSAL)
Apache License 2.0
545 stars 213 forks source link

osal_timer_UT inconsistent on MCP750 / VxWorks #1095

Open jphickey opened 3 years ago

jphickey commented 3 years ago

Describe the bug The timer test does not have consistent results when run on the MCP750 + VxWorks 6.9 platform

To Reproduce Run "osal_timer_UT" and occasionally a failure occurs in the "nominal" timer case:

[ PASS] 05.006 ut_ostimer_timerio_test.c:468 - OS_TimerSet(g_timerIds[4], startTime, intervalTime) (0) == OS_SUCCESS (0)
[ FAIL] 05.007 ut_ostimer_timerio_test.c:475 - 4# Nominal - callback status -1

Expected behavior Test should pass reliably

Code snips This is partly related to the fact that the MCP750 implementation has something wrong with its timer implementation. The test reports these warnings:

OS_TimeBaseSet_Impl():576:WARNING: timer 524301 start_time requested=1000us, configured=16666us
OS_TimeBaseSet_Impl():582:WARNING: timer 524301 interval_time requested=500000us, configured=516666us

This means there is increased jitter in the callbacks, which is then compounded by the rather crude delta check:

https://github.com/nasa/osal/blob/64a6b31b5448a6301c64b001e043d4c7d9570131/src/unit-tests/ostimer-test/ut_ostimer_test.c#L104

System observed on: MCP750 / VxWorks 6.9

Additional context Other timer tests which average the counts over total time pass fine. But this one checks the delta on every interval, so one case of too much jitter and it fails.

Reporter Info Joseph Hickey, Vantage Systems, Inc.

jphickey commented 3 years ago

I believe the issue here is specific to the MCP750, not really a bug in the test itself. Because it is configuring the kernel timer for 516666us instead of 500000us, the test case sees an absurd amount of jitter in the resulting callbacks. If the kernel could configure a 500000us timer properly, this test would run fine most likely.

skliper commented 3 years ago

Added milestone to ensure it gets documented in release notes (no "fix" required, it's related to resolution of the kernel timer on the MCP750).