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Apps should not pend forever on software bus #55

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jphickey opened this issue Apr 9, 2020 · 3 comments · May be fixed by #144
Open

Apps should not pend forever on software bus #55

jphickey opened this issue Apr 9, 2020 · 3 comments · May be fixed by #144
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enhancement New feature or request

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@jphickey
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jphickey commented Apr 9, 2020

The SAMPLE_APP, which is supposed to exemplify the current best practices, shouldn't be pending forever on a software bus message as it does here:

sample_app/fsw/src/sample_app.c

Lines 85 to 87 in b956292

status = CFE_SB_RcvMsg(&SAMPLE_AppData.MsgPtr,
SAMPLE_AppData.CommandPipe,
CFE_SB_PEND_FOREVER);

The problem with pending forever is that the app also needs to perform an orderly exit if a restart/reload/delete command is sent to ES, which is checked by CFE_ES_RunLoop(). If an app is pending forever for software bus messages but none are sent, then the shutdown request will remain pending indefinitely.
@jphickey
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jphickey commented Apr 9, 2020

Update - I did test this and confirm that the ES will actually forcibly delete the task via an OS_TaskDelete if it doesn't exit itself within the delay period. So the app actually will still get restarted, but forcibly deleting an app via that method is not good because it will leak any resources that the app was using at the time it was deleted.

As a best-practice example, it should use a time-limited pend on the software bus, so it can also poll the CFE_ES_RunLoop() function.

@jphickey jphickey added the enhancement New feature or request label Apr 9, 2020
@jphickey
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jphickey commented Apr 9, 2020

Calling this an "enhancement" rather than a "bug" because it is also saved by the fact that SCH_LAB by default sends a message every few seconds, so while less than ideal, its not fully broken.

@skliper skliper added this to the 1.2.0 milestone Apr 9, 2020
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skliper commented Apr 9, 2020

Added milestone, feel free to fix if you want

@skliper skliper removed this from the 1.2.0 milestone Aug 21, 2020
jphickey added a commit to jphickey/sample_app that referenced this issue Mar 29, 2021
@jphickey
Fix nasa#55, add timeout to SB receive
531a47f 
Apps should not pend forever on software bus receive, because
they should also periodically check CFE_ES_RunLoop even if no
commands were received.
@jphickey jphickey linked a pull request Mar 29, 2021 that will close this issue
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Fix #55, add timeout to SB receive jphickey/sample_app
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@jphickey @skliper