Task State Segment: Difference between revisions

For each CPU which executes processes possibly wanting to do system calls via interrupts, one TSS is required. The only interesting fields are SS0 and ESP0. Whenever a system call occurs, the CPU gets the SS0 and ESP0-value in its TSS and assigns the stack-pointer to it. So one or more kernel-stacks need to be set up for processes doing system calls. Be aware that a thread's/process' time-slice may end during a system call, passing control to another thread/process which may as well perform a system call, ending up in the same stack. Solutions are to create a private kernel-stack for each thread/process and re-assign esp0 at any task-switch or to disable scheduling during a system-call (see also [[Kernel Multitasking]]).