>>>>> "Sourav" == Sourav Chakraborty <[EMAIL PROTECTED]> writes:
Sourav> Hi, This is a bit of a general question,but however i would
Sourav> be glad if anyone could provide me with the pointers as how
Sourav> to assign priorities to various tasks for a real time
Sourav> system.
Here's one view that has served me well in building reliable systems:
Avoid the use of priority if at all possible, and if needed use it as
little as possible. Instead, have your tasks designed so they have
well defined completion time bounds (or time bounds for time to yield
the CPU to other tasks).
One of the nasty ways systems can fail is that they work fine until
presented with a very high load, at which point critical things don't
get done anymore because other things were given higher priority and
they now consume 100% of the CPU. If you don't use priority and your
tasks all have time bounds, this failure cannot happen, and your
system is stable under all loads.
To put it differently: if you use priority, it is far harder to prove
liveness and time bounds for any tasks other than the subset that uses
the highest priority. (And if you use interrupts, it gets even
harder.)
paul
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