Cooperative multitasking provides a technique where 2+ software programs are able to share the resources and time of a common host processor. Within this technique, the queue must be able to equally allocate the resources of the processor within the programs. That means tasks must release the CPU, allowing the next task a chance to run.
It is sometimes referred to as “non-preemptive multitasking.”
When using this structure, the operating system does not initiate a context switch from running one process to running another process. The processes will instead voluntarily yield control of the processor at times, when idle, or if blocked to enable other applications to run.
Most systems have switched away from cooperative multitasking today. Popular operating systems in the past, when using 16-bit applications, would use this process. Today, it is typically found in memory-constrained embedded systems and specific applications or subsystems.
List of the Advantages of Cooperative Multitasking
1. It is very easy to implement.
Cooperative multitasking is the best option for single users who have a few tasks that must be completed. You don’t need to worry about the presence of suspending code because each thread is responsible for when it gives up its coding time. That makes the coding processes much easier for the individual programmer, although the skill of the coder will dictate the effectiveness of the system.
2. It makes it easy to share data.
With this type of operating system, different individuals can share the same view, even if they are not on the same project at the same time. The processes involved are predictable, allowing for individualized testing and profiling, even if the incidents occur at different times. This allows for better efficiencies within the processes while maintaining a single CPU.
3. It offers a specific time frame for consideration.
Coding can include timers that setup events and loops that look for cooperative threads as processes are implemented. That means you’ll need to ensure that each thread accesses the processor to maximize its benefits without taking too long to access the resource. If a thread or program takes too long, then you’ll miss opportunities for progress.
To be fair, this exact process is less of a cooperative multitasking microkernel and more of a loop/timer implementation, though it is still classified as a process within this type of structure.
4. It maximizes what the CPU is able to provide.
Because cooperative multitasking takes single processes or threads at specific times, the CPU is able to dedicate its resources toward the specific item that is being run at the time. In other forms of multitasking, there may be multiple threads or programs running simultaneously, which reduces the effects of processing power that is available to each one. When coded effectively, cooperative multitasking maximizes the processing power because it has such a focus on individuality.
5. It provides fewer re-entrance problems.
When cooperative multitasking is implemented with a single CPU kernel, there are usually fewer re-entrance problems encountered. That is because the threads, programs, or tasks that are running cannot be arbitrarily interrupted by other tasks. The only interruptions which occur in this type of system are at positions that are at the kernel calls, which are permitted by the coder.
This advantage does not apply to multiprocessor kernels. It only applies with a single-processor kernel.
6. It allows for real-time responses to be fully preserved.
Although cooperative multitasking does impede responses at the task level, it fully preserves those responses on an interrupt handler. These handlers continue to use mailboxes and semaphores within the multitasking system, which allows the modules to run independently of the algorithms which are currently active.
List of the Disadvantages of Cooperative Multitasking
1. It is difficult to stop a task once it has started.
There is no way to suspend the thread that is currently operating when using cooperative multitasking. That means the thread which takes the resources of the CPU will continue to demand attention until the thread is completed. If an error occurs within the thread or program, or an execute does not occur, then the CPU may be forced into a position where the user must manually stop operations to restore its capabilities.
2. It does not guarantee that every task will be able to access the processor.
Because the threads operate independently of each other, there is no guarantee that every thread or program will be able to get the time with the CPU it requires. If the scheduling processes are not properly calculated, it is entirely possible to have some resources never access the processor without a manual intervention. In such a circumstance, projects take more time to complete because the cooperative multitasking performance must be continually reviewed.
3. It does not work well for certain response times.
Cooperative multitasking is best uses when programs don’t require a response time in the order of milliseconds or microseconds at the task level. If those timeframes are necessary, then a different structure is highly recommended.
The advantages and disadvantages of cooperative multitasking are typically used when a single user, with a handful of threads or programs, need to maximize local resources. Because of its natural limitations, group situations do not typically benefit from this type of process. There are always exceptions to the rule, of course, so be sure to examine all of your options before settling on the type of multitasking you’re going to employ.