gstreamer/gst/cothreads.c

144 lines
3.7 KiB
C
Raw Normal View History

#include <sys/time.h>
#include <linux/linkage.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <setjmp.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/mman.h>
#include "cothreads.h"
pthread_key_t _cothread_key = -1;
cothread_state *cothread_create(cothread_context *ctx) {
cothread_state *s;
if (pthread_self() == 0) {
s = (cothread_state *)malloc(sizeof(int) * COTHREAD_STACKSIZE);
} else {
char *sp = CURRENT_STACK_FRAME;
unsigned long *stack_end = (unsigned long *)((unsigned long)sp &
~(STACK_SIZE - 1));
s = (cothread_state *)(stack_end + ((ctx->nthreads - 1) *
COTHREAD_STACKSIZE));
if (mmap((char *)s,COTHREAD_STACKSIZE*(sizeof(int)),
PROT_READ|PROT_WRITE|PROT_EXEC,MAP_PRIVATE|MAP_ANONYMOUS,
-1,0) < 0) {
perror("mmap'ing cothread stack space");
return NULL;
}
}
s->ctx = ctx;
s->threadnum = ctx->nthreads;
s->flags = 0;
s->sp = (int *)(s + COTHREAD_STACKSIZE);
ctx->threads[ctx->nthreads++] = s;
// printf("created cothread at %p\n",s);
return s;
}
void cothread_setfunc(cothread_state *thread,cothread_func func,int argc,char **argv) {
thread->func = func;
thread->argc = argc;
thread->argv = argv;
thread->pc = (int *)func;
}
cothread_context *cothread_init() {
cothread_context *ctx = (cothread_context *)malloc(sizeof(cothread_context));
if (_cothread_key == -1) {
if (pthread_key_create(&_cothread_key,NULL) != 0) {
perror("pthread_key_create");
return NULL;
}
}
pthread_setspecific(_cothread_key,ctx);
memset(ctx->threads,0,sizeof(ctx->threads));
ctx->threads[0] = (cothread_state *)malloc(sizeof(cothread_state));
ctx->threads[0]->ctx = ctx;
ctx->threads[0]->threadnum = 0;
ctx->threads[0]->func = NULL;
ctx->threads[0]->argc = 0;
ctx->threads[0]->argv = NULL;
ctx->threads[0]->flags = COTHREAD_STARTED;
ctx->threads[0]->sp = CURRENT_STACK_FRAME;
ctx->threads[0]->pc = 0;
// fprintf(stderr,"0th thread is at %p\n",ctx->threads[0]);
// we consider the initiating process to be cothread 0
ctx->nthreads = 1;
ctx->current = 0;
return ctx;
}
cothread_state *cothread_main(cothread_context *ctx) {
// fprintf(stderr,"returning %p, the 0th cothread\n",ctx->threads[0]);
return ctx->threads[0];
}
void cothread_stub() {
cothread_context *ctx = pthread_getspecific(_cothread_key);
register cothread_state *thread = ctx->threads[ctx->current];
thread->flags |= COTHREAD_STARTED;
thread->func(thread->argc,thread->argv);
thread->flags &= ~COTHREAD_STARTED;
thread->pc = 0;
// printf("uh, yeah, we shouldn't be here, but we should deal anyway\n");
}
void cothread_switch(cothread_state *thread) {
cothread_context *ctx;
cothread_state *current;
int enter = 0;
// int i;
if (thread == NULL)
return;
ctx = thread->ctx;
current = ctx->threads[ctx->current];
if (current == NULL) {
fprintf(stderr,"there's no current thread, help!\n");
exit(2);
}
if (current == thread) {
fprintf(stderr,"trying to switch to same thread, legal but not necessary\n");
return;
}
// find the number of the thread to switch to
ctx->current = thread->threadnum;
// fprintf(stderr,"about to switch to thread #%d\n",ctx->current);
/* save the current stack pointer, frame pointer, and pc */
__asm__("movl %%esp, %0" : "=m"(current->sp) : : "esp", "ebp");
enter = setjmp(current->jmp);
if (enter != 0)
return;
enter = 1;
/* restore stack pointer and other stuff of new cothread */
__asm__("movl %0, %%esp\n" : "=m"(thread->sp));
if (thread->flags & COTHREAD_STARTED) {
// switch to it
longjmp(thread->jmp,1);
} else {
// start it
__asm__("jmp " SYMBOL_NAME_STR(cothread_stub));
}
}