_Project B Notes_  (Michael Safyan)

*Milestones*

   1. Non-preemptive
          * Create a thread
          * Yield
          * Exit
   2. Same as #1, but adds priorities
   3. Preemption, synchronization primitives.

    _*NOTE*_: Milestones can be implemented in any order, but will be 
more straightforward if done in order above.

*Preemption
*
    Generating the interrupt is easy; handling it /correctly/ is 
difficult. Interrupt may be interrupted.

*B-Public.txt*

    * Skeleton of milestone #3.
    * Creates 8 worker threads ("thr_compute").
    * Creates 1 monitoring thread ("thr_mon").
    * tickSz=0 is a special case => non-preemptive.
    * "uthr_destroy" (destructor to "uthr_create" constructor) not in
      spec, but can be created/added as desired.

*Ucontext-basic.txt*

    * Context created with "getcontext", "makecontext".
    * Swap between context with "swapcontext".
    * swapcontext(&from,&to) means:
          o Save current context into "from".
          o Jump to context stored in "to".
    * swapcontext is similar to "setjmp" followed by "longjmp", but uses
      "trampoline" (details: "/usr/include/ucontext.h").

*Context
*
Context contains:

    * Machine/hardware context (i.e. hardware registers)
          o Stack Pointer (SP)
          o Program Counter (PC) [Intel terminology: Instruction Pointer
            (IP)]
          o General purpose registers (e.g. "EAX", "EBX", "ECX", "EDX",
            etc. in x86; "r0", "r1", etc. RISC-like CPU)
          o ...
    * Software context (e.g. signal mask)

*Addendum

*Official documentation for "ucontext.h":
http://www.opengroup.org/onlinepubs/009695399/basedefs/ucontext.h.html

Functions "getcontext", "makecontext", and "swapcontext" are defined in 
the X/Open System Interfaces Extension (XSI).