OS is the program that handeles all the hardwares and software, manage all the resources (CPU , memory ). Kernel is the Heart of OS. Kernel is not a process. It is Process manager. Kernel is set of ISR (Interrupt Service Routine) . So when user process wants service from kernel it cause Interrupt. This is called software interrupt. and then CPU mode changes from user mode to kernel mode. Kernel serves the process with already written ISR. and once finish the control returns to User mode and start process from the interupted point.

So you can call Kernel as Server and all processes as clients. There are multiple clients
some times wants the same sercvices . Its the responsibility of Server to handle this situation.
(multiprocessing)
............................................. Dont worry Linux Kernel perform this very well !