Improve handling of tasks on BSP and AP CPUs #278
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Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
Running test_main() as a task on BSP blocks scheduling and execution of other tasks on BSP (chicken-egg problem), which get created and scheduled from within the test_main() itself. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
In the wait_for_all_cpus() wait for all unfinished CPUs and/or CPUs without empty task_queue. But do not wait for BSP as it typically is the expected caller of this function. Also, do not unlink CPU struct from the cpus list, there might be more task upcoming. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
All AP CPUs after empting their task_queue get into blocked state, which makes run_tasks() wait on them until they get unblocked. The BSP is never waited on as it is supposed to unblock the AP CPUs. After an unblock, run_tasks() sets the CPU into unfinished state, before executing any tasks from the task_queue. That way BSP controls when all APs start executing their tasks and when they are finished with it. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
The execute_tasks() helper is responsible for collectively unblocking all CPUs, calling run_tasks() on BSP CPU and waiting for all AP CPUs untile they are finished. In kernel_main the execute_tasks() is called before test_main() just in case. Currently there are no tasks scheduled before the test_main(). The execute_tasks() called after the test_main() makes sure all APs and the BSP get unblocked and their tasks executed or the states of the CPUs are set to finished. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
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