zephyr/tests/kernel/timer/starve
Peter Bigot 7e71164cc6 tests: kernel: timer: add test for starvation
Add a test that repeatedly reschedules a timer before it expires, and
has no other timers active.  If the timer internal state overflows due
to counter wrap either the uptime or the tick counter may appear to go
backwards.  The test runs until it fails, or until a specified amount
of measured time has passed.

This test is build-only for automated test programs as the default
limit to pass is one hour, and some platforms may require an even
longer period.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
2019-12-02 15:28:12 +01:00
..
src tests: kernel: timer: add test for starvation 2019-12-02 15:28:12 +01:00
CMakeLists.txt tests: kernel: timer: add test for starvation 2019-12-02 15:28:12 +01:00
Kconfig tests: kernel: timer: add test for starvation 2019-12-02 15:28:12 +01:00
prj.conf tests: kernel: timer: add test for starvation 2019-12-02 15:28:12 +01:00
README.txt tests: kernel: timer: add test for starvation 2019-12-02 15:28:12 +01:00
testcase.yaml tests: kernel: timer: add test for starvation 2019-12-02 15:28:12 +01:00

Title: Timer Starvation test

The purpose of the test is to detect whether the timer implementation
correctly handles situations where only one timeout is present, and that
timeout is repeatedly rescheduled before it has a chance to fire.  In
some implementations this may prevent the timer interrupt handler from
ever being invoked, which in turn prevents an announcement of ticks.
Lack of tick announcement propagates into a monotonic increase in the
value returned by z_clock_elapsed().

This test is not run in automatic test suites because it generally takes
minutes, hours, or days to fail, depending on the hardware clock rate
and the tick rate.  By default the test passes if one hour passes
without detecting a failure.

Failure will occur when some counter wraps around.  This may be a
hardware timer counter, a timer driver internal calculation of
unannounced cycles, or the Zephyr measurement of unannounced ticks.

For example a system that uses a 32768-Hz internal timer counter with
24-bit resolution and determines elapsed time by a 24-bit unsigned
difference between the current and last-recorded counter value will fail
at 512 s when the updated counter value is observed to be less than the
last recorded counter.

Systems that use a 32-bit counter of 80 MHz ticks would fail after
53.687 s.