Chapter 4 - DSpace at Waseda University

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Chapter 4
bugs per 1000 lines”. It means there is a possibility of a problem occurrence in
embedded systems. Generally, as the development period of an embedded system is
pretty short, it lacks enough test and verification. Therefore, we need to consider how
to solve such a problem. The answer is to solve quickly using event logs when a
problem occurred. It is a job of a developer or an administrator to find out the cause
of the problem.
4.2.1.3 Process Flow of DL
In DL, a problem is found by logged event information. To find a problem by using KAS, it
is needed to define the problem which one would like to find out (for instance, for timer:
algorithm on whether a timer has passed deadline or not). It is easy to define the timer latency
problem because we only need to check whether it passed the deadline of a process. In Figure
4.4 HRTimer_Tick means the deadline (expired time of task) of a high-resolution timer and
HRTimer_Latency means the whole time before the high-resolution timer expired (including
latency). Therefore, the problem of a timer can be defined as whether running time of a
certain process has passed or not passed to the deadline.
Figure 4.5 is the flow of DL’s processing. Firstly, as shows in Figure 4.4, DL defines a
problem and checks the whole data from the top to bottom and find out problems. If the
problems are not found, it continues to check without any results but if there is a problem, it
saves the line information and checks how many times the problem has occurred. When the
search is finished to the bottom, Separation Layer, which is the next layer, will be processed.