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user-level thread code from http://homepage.cs.uiowa.edu/~jones/opsys/threads/

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master
orange 11 years ago
parent fcdc22b861
commit a0999008e0
5 changed files with 598 additions and 1 deletions
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2
.gitignore vendored
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*~
.*.swp
*.o
approximate-pi
linked-list
mandelbrot
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binsearch
test-inline-assembly
test-inline-assembly.s
uiowa-threads-example

5
Makefile
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CFLAGS=-std=c99 -Wall -g -O2
INDENTOPTS=-kr --no-tabs --braces-on-func-def-line --indent-level2
TARGETS=approximate-pi linked-list mandelbrot threads circular-buffer structs ncurses-pong bit-fuckery bit-fuckery2 checkcheck multibrot bloom wo-lernen lua-foo binsearch test-inline-assembly
TARGETS=approximate-pi linked-list mandelbrot threads circular-buffer structs ncurses-pong bit-fuckery bit-fuckery2 checkcheck multibrot bloom wo-lernen lua-foo binsearch test-inline-assembly uiowa-threads-example
EXTRAS=mandelbrot.bmp multibrot.png test-inline-assembly.s
.PHONY: all
@ -40,3 +40,6 @@ test-inline-assembly: test-inline-assembly.c
test-inline-assembly.s: test-inline-assembly.c
$(CC) -Wall -S -o $@ $<
uiowa-threads-example: uiowa-threads.o uiowa-threads-example.c
$(CC) $(CFLAGS) -o $@ $^

29
uiowa-threads-example.c
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/****
* file example.c
*
Program to demonstrate the thread management package *
Written by Douglas Jones, Feb 18, 1998 *
****/
#include <stdio.h>
#include "uiowa-threads.h"
void test_thread( int n )
{
printf( "A%d\n", n );
if (n > 1) thread_launch( 4000, test_thread, n-1 );
thread_relinquish();
printf( "B%d\n", n );
thread_relinquish();
printf( "C%d\n", n );
thread_relinquish();
}
int main()
{
thread_manager_init();
thread_startup_report(); /***********/
thread_launch( 4000, test_thread, 5 );
thread_manager_start();
/* control never reaches this point */
}

486
uiowa-threads.c
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/****
* file threads.c
*
A partial implementation of a user-level thread package
Written by Douglas Jones, Feb 17, 1998
Updated with minor bug fix in thread_exit, Feb 19, 1998
Updated so free called on original stack, Feb 19, 2002
Updated with defines for _longjmp, Aug 13, 2002
Copyright Douglas Jones, 1998.
Permission is hereby granted to make and modify
personal copies of this code for noncommercial or
educational use.
*
All other rights are reserved! *
****/
#include <stdio.h>
#include <stdlib.h>
#include <setjmp.h>
/* just in case this isn't compiled on a UNIX system
we back off to use the standard setjmp and longjmp.
UNIX systems have _setjmp that just does control
transfers, and then setjmp (no underscore) that also
saves the signal masks. Saving those makes sense
for exception handlers, but not for coroutines.
*/
#ifndef _setjmp
#define _setjmp setjmp
#endif
#ifndef _longjmp
#define _longjmp longjmp
#endif
/****
* PART I: -- Reverse Engineer the jump buffer *
* This is the key to user-level context switching *
****/
/**** *
* tools used by studyit to understand jump buffer structure *
* ****/
static int * low_bound; /* below probe on stack */
static int * probe_local; /* local to probe on stack */
static int * high_bound; /* above probe on stack */
static int * prior_local; /* value of probe_local from earlier call */
static jmp_buf probe_env; /* saved environment of probe */
static jmp_buf probe_sameAR; /* second environment saved by same call */
static jmp_buf probe_samePC; /* environment saved on previous call */
static jmp_buf * ref_probe = &probe_samePC; /* switches between probes */
/****
* reports from studyit giving results of study
* -- our focus here is on learning how to make
a jump buffer that points to newly allocated *
activation record on the heap *
****/
static int stack_direction; /* +1 if stack grows up, -1 if down */
long int local_offset; /* lowest location in AR from local vars */
jmp_buf probe_record; /* nonzero entries mean fields that change */
/****
* code to explore the activation record *
* and jump buffer structure *
****/
void boundhigh()
/* purpose: set high_bound to a local variable beyond probe on stack */
{
int c;
high_bound = &c;
}
void probe()
/* purpose: probe the activation record and jump buffer structure */
{
int c;
prior_local = probe_local;
probe_local = &c;
_setjmp( *ref_probe );
ref_probe = &probe_env;
_setjmp( probe_sameAR );
(void) boundhigh();
}
void boundlow()
/* purpose: set low_bound to a local variable before probe on stack */
{
int c;
low_bound = &c;
(void) probe();
}
void fill()
/* purpose: put some padding on the stack and then study the result */
{
(void) boundlow();
}
static void studyit()
/* purpose: study the result of probes */
{
if (sizeof(long int) != sizeof(long int *)) {
fprintf( stderr, "Pointer size is wrong\n" );
}
if (((long int)high_bound) > ((long int)low_bound)) {
/* stack grows up */
stack_direction = 1;
} else {
/* stack grows down */
stack_direction = -1;
}
/* study the jump buffer */
{
int i;
long int * p;
long int * sameAR;
long int * samePC;
long int * probe_rec;
long int prior_diff = (long int)probe_local
- (long int)prior_local;
long int min_frame = (long int)probe_local;
/* following line views jump buffer as array of long int */
p = (long int *)probe_env;
sameAR = (long int *)probe_sameAR;
samePC = (long int *)probe_samePC;
probe_rec = (long int *)probe_record;
for (i = 0; i < sizeof(jmp_buf); i += sizeof(long int) ) {
*probe_rec = 0;
if (*p != *samePC) {
if (*p != *sameAR) {
fprintf( stderr, "No Thread Launch\n" );
exit(-1);
}
if ((*p - *samePC) == prior_diff) {
/* record frame dependency */
*probe_rec = 1;
if (stack_direction == 1) { /* up */
if (min_frame > *p) {
min_frame = *p;
}
} else { /* grows down */
if (min_frame < *p) {
min_frame = *p;
}
}
}
}
p++, sameAR++, samePC++, probe_rec++;
}
if (stack_direction == 1) { /* grows up */
local_offset
= (long int)probe_local - min_frame;
} else { /* stack grows down */
local_offset
= min_frame - (long int)probe_local;
}
}
}
void thread_startup_report()
/* reports on the results of the study done by above code */
{
int i;
long int * jb;
printf( "Thread startup study results\n" );
if (stack_direction == 1) {
printf( " Stack grows up\n" );
} else {
printf( " Stack grows down\n" );
}
printf( " Local variable offset from AR base = %1d\n", local_offset );
printf( " Jump buffer fields subject to modification:\n" );
jb = (long int *)probe_record;
for (i = 0; i < sizeof(jmp_buf); i += sizeof(long int) ) {
if (*jb != 0) {
printf( " %1d\n", i );
}
jb++;
}
printf( " Jump buffer size: %1d\n", sizeof(jmp_buf) );
}
/****
* PART II: -- The Thread Manager *
* Based on the results reported by Part I *
****/
/**** *
* thread data types *
* ****/
struct thread {
struct thread * next; /* used to link threads into queues */
int size; /* the size of the thread */
void (* proc)(int); /* procedure for body of thread */
int param; /* parameter to base procedure */
jmp_buf state; /* the state of the thread */
/* size bytes of stack follow here */
};
#define thread_null (struct thread *)0
struct thread_queue {
struct thread * head;
struct thread * tail;
};
/**** *
* Fundamental scheduler data structures *
* ****/
static struct thread_queue readylist; /* the list of all ready threads */
static struct thread * current; /* the current running thread */
static void * mem_to_free; /* anything to be passed to free() */
static char * thread_error; /* string giving package death cause */
static jmp_buf thread_death; /* used on thread package death */
static jmp_buf go_free_it; /* used to call free from original stk */
/**** *
* code for thread_queue data type *
* ****/
static void thread_queue_init( struct thread_queue * q )
/* initialize q */
{
q->head = thread_null;
q->tail = thread_null;
}
static void thread_enqueue( struct thread * t, struct thread_queue * q )
/* enqueue t on q */
{
t->next = thread_null;
if (q->head == thread_null) {
q->head = t;
q->tail = t;
} else {
q->tail->next = t;
q->tail = t;
}
}
static struct thread * thread_dequeue( struct thread_queue * q )
/* dequeue and return a thread from q */
{
if (q->head == thread_null) {
return thread_null;
} else {
struct thread * t;
t = q->head;
q->head = t->next;
return t;
}
}
/**** *
* user callable thread management routines *
* ****/
void thread_manager_init()
/* call this once before launching any threads */
{
/* first study current system and see if thread launch worth trying */
(void) fill(); /* do a probe with filler on stack */
(void) boundlow(); /* do a probe without filler */
(void) studyit(); /* figure out what it all means */
/* now build thread manager data structures */
thread_queue_init( &readylist );
mem_to_free = (void *)0;
current = thread_null;
}
void thread_manager_start()
/* call this once after launching at least one thread */
/* this only returns when all threads are blocked! */
{
current = thread_dequeue( &readylist );
if (current == thread_null) {
/* crisis */
fprintf(stderr, "Thread manager start failure, no threads!\n");
exit(-1);
}
if (_setjmp( thread_death )) {
/* comes here when _longjmp( thread_death, 1 ) done */
fprintf(stderr,
"Thread manager terminated, %s!\n", thread_error );
if (mem_to_free != (void *)0 ) {
/* see comments below */
free( mem_to_free );
}
} else {
/* we will come back here whenever we need to deallocate */
(void) _setjmp( go_free_it );
if (mem_to_free != (void *)0 ) {
/* it's not safe to call free() anywhere but on the
real stack, so once the thread manager is running,
this is the only safe place to call it!
*/
free( mem_to_free );
mem_to_free = (void *)0;
}
_longjmp( current->state, 1 );
}
}
void thread_relinquish()
/* call this within a thread to allow scheduling of a new thread */
{
if (_setjmp( current->state ) == 0) {
thread_enqueue( current, &readylist );
current = thread_dequeue( &readylist );
_longjmp( current->state, 1 );
}
}
void thread_exit()
/* call this within a thread to terminate that thread */
{
/* we can't deallocate, so we schedule this thread for deallocation */
mem_to_free = (void *)current;
/* now, get the next thread to run */
current = thread_dequeue( &readylist );
if (current == thread_null) {
/* crisis */
thread_error = "ready list empty";
_longjmp( thread_death, 1 );
}
_longjmp( go_free_it, 1 );
}
void thread_launch( int size, void (* proc)(int), int param )
/* call this to launch proc(param) as a thread */
/* may be called from main or from any thread */
{
struct thread * t;
t = (struct thread *)malloc( sizeof(struct thread) + size );
t->size = size;
t->proc = proc;
t->param = param;
if (_setjmp( t->state )) {
/* comes here only when new thread scheduled first time */
(*current->proc)(current->param);
thread_exit();
}
/* continue initialization */
{
long int * s;
long int * probe_rec;
long int local_base = (long int)&t; /* address of local t */
long int new_base;
int i;
/* the following code copies the contents of the
activation record, just in case it might prove
useful; note that we don't know that this is
needed on any machine, but it might, so we do it. */
if (stack_direction == 1) { /* grows up */
long int * src;
long int * dst;
new_base = (long int)t + sizeof( struct thread )
+ local_offset;
src = (long int *) (local_base - local_offset);
dst = (long int *) (new_base - local_offset);
for (i = 0; i <= local_offset; i += sizeof(long int)) {
*dst++ = *src++;
}
} else { /* grows down */
long int * src;
long int * dst;
new_base = (long int)t + sizeof( struct thread )
+ size - (local_offset + sizeof(long int));
src = (long int *) (local_base);
dst = (long int *) (new_base);
for (i = 0; i <= local_offset; i += sizeof(long int)) {
*dst++ = *src++;
}
}
/* the following code adjusts the references to the
activation record in the saved thread state so that
they point to the base of the newly allocated stack */
s = (long int *)(t->state);
probe_rec = (long int *)probe_record;
for (i = 0; i < sizeof(jmp_buf); i += sizeof(long int) ) {
if (*probe_rec != 0) {
/* adjust this field of state */
*s += new_base - local_base;
}
s++;
probe_rec++;
}
}
thread_enqueue( t, &readylist );
}
void thread_free( void * ptr )
/* call this from within threads instead of free, because some
heap managers are paranoid enough to forbid a call to free
when the stack itself is in a block allocated in the heap */
{
mem_to_free = ptr;
if (_setjmp( current->state ) == 0) {
_longjmp( go_free_it, 1 );
}
/* after call to free(), there will be a longjmp back to here */
}
void thread_safety_check()
/* call this to check for thread stack overflow */
{
long int t = (long int)current + sizeof(struct thread);
if ( ((long int)&t < t) || ((long int)&t > (t + current->size)) ) {
/* crisis */
thread_error = "thread stack overflow";
_longjmp( thread_death, 1 );
}
}
/**** *
* thread manager extension for semaphores *
* ****/
/* semaphore representation known only to semaphore methods */
struct thread_semaphore {
int count;
struct thread_queue queue;
};
/* methods applying to semaphores */
void thread_semaphore_init( struct thread_semaphore * s, int v )
/* call this to initialize semaphore s to a count of v */
{
s->count = v;
thread_queue_init( &s->queue );
}
void thread_wait( struct thread_semaphore * s )
/* call this within a thread to block on a semaphore */
{
if (s->count > 0) {
s->count--;
} else {
if (_setjmp( current->state ) == 0) {
thread_enqueue( current, &s->queue );
current = thread_dequeue( &readylist );
if (current == thread_null) {
/* crisis */
thread_error = "possible deadlock";
_longjmp( thread_death, 1 );
}
_longjmp( current->state, 1 );
}
}
}
void thread_signal( struct thread_semaphore * s )
/* call this within a thread to signal a semaphore */
{
struct thread * t = thread_dequeue( &s->queue );
if (t == thread_null) {
s->count++;
} else {
thread_enqueue( t, &readylist );
}
}

77
uiowa-threads.h
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/****
* file threads.h
*
Header files for the user-level thread package
Written by Douglas Jones, Feb 18, 1998
Added thread_free interface, Feb 19, 2002
Copyright Douglas Jones, 1998.
Permission is hereby granted to make and modify
personal copies of this code for noncommercial or
educational use.
*
All other rights are reserved! *
****/
/**** *
* Initialization routines *
* ****/
void thread_manager_init();
/* call this once before launching any threads */
void thread_launch( int size, void (* proc)(int), int param );
/* call this to launch proc(param) as a thread */
/* may be called from main or from any thread */
void thread_manager_start();
/* call this once after launching at least one thread */
/* this only returns when all threads are blocked! */
/**** *
* Routines to call from within a thread *
* ****/
void thread_relinquish();
/* call this within a thread to allow scheduling of a new thread */
void thread_exit();
/* call this within a thread to terminate that thread */
void thread_free( void * ptr );
/* call this within a thread instead of calling free() */
/* note, thread_launch() may also be called within a thread */
/**** *
* Utility and debugging routines *
* ****/
void thread_startup_report();
/* reports on the results of the study done in the startup */
void thread_safety_check();
/* call this to check for thread stack overflow */
/**** *
* Semaphore extension to thread package *
* ****/
/* the declaration of the semaphore type given here is a lie! */
struct thread_semaphore {
void * unused_fields[3];
};
void thread_semaphore_init( struct thread_semaphore * s, int v );
/* call this to initialize a semaphore */
void thread_wait( struct thread_semaphore * s );
/* call this within a thread to block on a semaphore */
void thread_signal( struct thread_semaphore * s );
/* call this within a thread to signal a semaphore */
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