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= Deadlock Break Benchmark
This benchmark measures the average time to break a deadlock that occurs
when a high priority task preempts a low priority task that is holding a
resource that the high priority task needs. In RTEMS, these situations
are mitigated through use of a semaphore with priority inheritance. A
task holding a semaphore with priority inheritance enabled has its
priority boosted to match that of the highest priority task blocked on
that semaphore.
== Directives
* rtems_semaphore_obtain
* rtems_semaphore_release
* rtems_task_suspend
* rtems_task_resume
== Methodology
This benchmark is structured in a way that is very similar to the semaphore-
shuffle benchmark, but instead uses three tasks of differing priorities and
suspend/resume instead of yield directives.
The benchmark is run and timed once with no semaphore operations. This is the
overhead time. The benchmark starts with the high priority task, which suspends
itself, passing control to the mid priority task. The mid priority task then
suspends itself, passing control to the low priority task. The low priority task
resumes the mid priority task, which then resumes the high priority task. The
process is repeated a total of BENCHMARKS times. This process is then executed
with the low priority task holding a semaphore that the high priority task blocks
on when trying to obtain. Due to priority inheritance (the deadlock break
mechanism) the low priority task will execute instead of the mid priority task.
The same system of suspend/resumes then occurs.
The average is found and the overhead (the time of the first run) is subtracted
out in the call to put_time.
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