Scheduler timer bugfix + documentation updates #2107
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This removes a race condition between calling has_expired() and the timeslice actually expiring.
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The other issue with the current interface is a user could call |
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I'm nominating this for release-blocker. |
bradjc
approved these changes
Sep 18, 2020
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bors r+ |
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Build failed: |
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bors retry |
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Pull Request Overview
This pull request fixes a potential (though as of yet undetected) bug in the kernel's use of the SchedulerTimer trait, where the kernel checked for expiration of the timer, then checked the amount of time remaining, not considering the possibility that the timer could wraparound in period between those checks, causing the kernel to read an invalid time remaining value. This was identified by @bradjc .
Rather than just fix the bug, we decided to change the interface slightly to make this misuse impossible -- rather than separate
has_expired()andget_remaining_us()functions, there is now only aget_remaining_us()function, which returnsNoneif the timer has expired.This PR also includes lots of documentation updates by @bradjc that clarify the
SchedulerTimerinterface further.Testing Strategy
This pull request was tested by running several apps simultaneously on Imix, incuding whileone, and verifying that timeslice expiration still works as expected.
TODO or Help Wanted
N/A
Documentation Updated
Formatting
make prepush.