OS

Pickle risc will run a multitasking OS.

Design

Microkernels are cool.

Functionatity in kernel

Scheduler
IPC
- Message passing
  - Synchronous
    - Blocking and non-blocking mode
    - Small fixed payload
      - Registers only?
- Shared memory
  - sharemem
    - "Share this page of my memory to that process"
    - returns some sort of ID uniquely identifying the share
  - mmap can take the ID from previous step to map the memory
Memory / paging

Functionality in servers

UART driver
Disk driver
Filesystem
Timer
Networking
Synchronization & locking

Semaphores & locking

Process can only block on message sending / receiving
Mutex impl -- a little like futex in Linux
- Atomic variable
  - 0: unlocked
  - 1: locked, noone is waiting
  - =2 : locked, waiting processes
- Sends message to synchronization server
  - Block on this
    - How is the lock object identified?
      - the sync server should not need (privileged) access to memory mappings
      - Lock objects carries ID inside?