Fix #274: Avoid possible deadlock of timer callback #278
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If the tick_time from the wait routine was perpetually greater than the interval time, eventually the wait_time became such that it was always below zero. Once this occurs, application callbacks would cease entirely. To avoid this, run the callback condition in a loop for periodic timers only (not for one-shot config).
skliper
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Oct 23, 2019
skliper
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Oct 29, 2019
ghost
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CCB 20191030 - Code reviewed and approved |
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Describe the contribution
Fix issue #274, avoids timer callback deadlock if actual tick_time is consistently bigger than the configured iinterval_time.
Testing performed
Modify
timer-testto choose an interval that is not a multiple of the system clock tick, such that it will be rounded up to the next tick by the implementation.Verify that evenually, two callbacks are generated in a single time tick, such that the long-term average of callbacks over time is consistent with the configured interval_time.
Confirm that callbacks continue normally until the application is stopped, as expected.
Expected behavior changes
Callbacks no longer cease once the "overrun" condition occurs (callbacks behind by >=1 full interval time)
Confirm consistent behavior on POSIX, RTEMS, and VxWorks
System(s) tested on:
Ubuntu 18.04.2 LTS 64-bit (POSIX/simulation)
RTEMS 4.11 pc686 BSP running in QEMU
MPC750 VxWorks 6.9
Contributor Info
Joseph Hickey, Vantage Systems, Inc.