coroutines

Table of Contents Coroutines Python asyncio 3.7 asyncio basics gevent MicroPython uasyncio CircuitPython QuickThreads QuickThreads Internals LLVM Coroutine Libtask Node.js SystemC sc_cor_pkg abstract class sc_cor abstract class UNIX SYSV: setcontext data structure getcontext(ucontext_t *ucp) setcontext(ucontext_t *ucp) makecontext(ucontext_t *ucp, void (*func)(), int argc, ...) UNIX: SETJMP

Coroutines

• Coroutines: https://en.wikipedia.org/wiki/Coroutine
• Fibers: https://en.wikipedia.org/wiki/Fiber_(computer_science)

Python

asyncio

• asyncio: https://docs.python.org/3/library/asyncio.html
• coroutines: https://docs.python.org/3/library/asyncio-task.html
  • original coroutine proposal
• internals
  • asyncio internals
  • how async/await works in asyncio
• tutorials
  • asyncio for the working programmers
  • asyncio walk-throughs

3.7 asyncio basics

• three ways to run a couroutine
  • asyncio.run(coro())
  • await coro()
  • task1 = asyncio.create_task(coro()); await task1
• three awaitable objects: can be used in an await expression
  • coroutine
  • asyncio.Task
  • asyncio.Future

gevent

• tutorials
  • gevent for the workking programmers: http://sdiehl.github.io/gevent-tutorial/

MicroPython

uasyncio

• uasyncio: https://github.com/peterhinch/micropython-async
  • forum: https://forum.micropython.org/viewtopic.php?f=15&t=85
  • tutorial (great!): https://github.com/peterhinch/micropython-async/blob/master/TUTORIAL.md

CircuitPython

• Cooperative Multitasking in CircuitPython with asyncio

QuickThreads

• qt: use version inside SystemC package
• David Keppel's TR
• SystemC: quickthreads vs setcontext
  • Extending SystemC threads to IA64

QuickThreads Internals

• QuickThreads Internals

LLVM Coroutine

• Coroutines in LLVM: http://llvm.org/docs/Coroutines.html

Libtask

• Coroutine library for C/Unix: https://swtch.com/libtask -- not sure if this is a good library

Node.js

• https://nodejs.org/api/events.html

SystemC

sc_cor_pkg abstract class

class sc_cor_pkg {
  public:
   ...        
   virtual sc_cor* create(size_t stack_size,sc_cor_fn* fn, void* arg );
   virtual void yield( sc_cor* next_cor ); // yield to function assoc. with next_cor
   virtual void abort( sc_cor* next_cor ); // quit and transfer control to next_cor
   ...
};

sc_cor abstract class

• wait: suspend a thread -- internally calls sc_cor_pkg::yield

UNIX SYSV: setcontext

• user-level context switching facility
• setcontext wiki: https://en.wikipedia.org/wiki/Setcontext
• Copmplete Context Control: http://www.delorie.com/gnu/docs/glibc/libc_465.html
• Non-Local Exits (GNU C Library): http://www.delorie.com/gnu/docs/glibc/libc_461.html
• boost.Context: http://www.boost.org/doc/libs/1_55_0/libs/context/doc/html/index.html

data structure

typedef struct ucontext {
  // context which will be resumed when current context terminates.
  // in case the current context was created using makecontext 
  struct ucontext *uc_link;      
  sigset_t         uc_sigmask;  // in <signal.h>
  stack_t          uc_stack;    // in <signal.h>
  // machine-specific representation of saved context, including calling
  // thread's machine registers
  mcontext_t       uc_mcontext; 
  ...
} ucontext_t;

getcontext(ucontext_t *ucp)

• save current context into "ucp"

setcontext(ucontext_t *ucp)

• restores the user context pointed at by ucp
• successful call does not return (just jump!)
• ucp should have been obtained by
  • getcontext() or
  • makecontext() or
  • passed as third argument to a signal handler

makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)

• initial setup:
  • getcontext(ucp): saves current context into ucp
  • allocate a stack space in ucp->uc_stack
  • define successor context and assign it to ucp->uc_link
  • makecontext(ucp, foo, args):
• later:
• setcontext(ucp) is called or swapcontext() is called
• foo(args) is called
• when foo(args) returns, successor context (uc_link) is activated

UNIX: SETJMP