#include <sim.h>

Collaboration diagram for sim_thread:

Data Fields
struct sim *	st_sim

void *	st_stack

unsigned	st_size

ucontext_t	st_ctx

struct m0_tlink	st_block

sim_time_t	st_blocked

struct sim_callout	st_wake

uint64_t	st_magic

Detailed Description

A thread in a simulated world.

Conceptually, a thread can always be replaced by a collection of call-outs. A thread is advantageous and natural to use when there is a lot of state to be maintained between call-outs and this state cannot be readily stored in some data-structure hanging off sim_callout::sc_datum. A thread uses native C language stack to store the state.

Threads interact with the simulation by sleeping (sim_sleep()), waiting on channels (struct sim_chan) and posting call-outs.

Current thread uses ucontext functions to implement lightweight and simple user-level threads. Blocking system call made from a sim_thread blocks the whole simulation.

With threads there are two modes in which simulation can be at the moment:

"thread mode", when one of the threads is running. In this mode the code
is executed on the thread's stack;

"scheduler mode", when no thread is running and simulation state is
advanced by main simulation loop running on a stack where sim_run() was
called, executing call-outs.

Note that this distinction is similar to "process" vs. "interrupt" modes of a traditional UNIX kernel.

A switch from thread to scheduler mode occurs when a thread is suspended (e.g., to wait on a channel) or exits. A switch in the opposite direction happens when a thread is resumed (e.g., woken up or starts for the first time).

Definition at line 202 of file sim.h.

Field Documentation

◆ st_block

struct m0_tlink st_block

linkage into a sim_chan::ch_threads list

Definition at line 215 of file sim.h.

◆ st_blocked

sim_time_t st_blocked

time when a thread was parked onto a channel. See sim_chan_wait() comments.

Definition at line 219 of file sim.h.

◆ st_ctx

ucontext_t st_ctx

platform-independent structure holding thread machine state (registers and signals mask usually)

Definition at line 212 of file sim.h.

◆ st_magic

uint64_t st_magic

Definition at line 224 of file sim.h.

◆ st_sim

struct sim* st_sim

simulation instance this thread is a part of

Definition at line 204 of file sim.h.

◆ st_size

unsigned st_size

size of allocated stack

Definition at line 208 of file sim.h.

◆ st_stack

void* st_stack

allocated native stack, allocated in sim_thread_init()

Definition at line 206 of file sim.h.

◆ st_wake

struct sim_callout st_wake

pre-allocated callout to wake the thread. Used by sim_sleep() and sim_chan_{signal,broadcast}().

Definition at line 223 of file sim.h.

The documentation for this struct was generated from the following file:

desim/sim.h

Data Fields