gstreamer/gst/cothreads.c

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/* GStreamer
* Copyright (C) 1999,2000 Erik Walthinsen <omega@cse.ogi.edu>
* 2000 Wim Taymans <wtay@chello.be>
*
* cothreads.c: Cothreading routines
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Library General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this library; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*/
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <setjmp.h>
#include <unistd.h>
#include <sys/mman.h>
Changes made to the DEBUG system. New header file gstdebug.h holds the stuff to keep it out of gst.h's hair. DEBUG ... Original commit message from CVS: Changes made to the DEBUG system. New header file gstdebug.h holds the stuff to keep it out of gst.h's hair. DEBUG prints out the process id, cothread id, source filename and line number. Two new macros DEBUG_ENTER and DEBUG_LEAVE are used to show the entry and exit of a given function. This eventually might be used to construct call trace graphs, even taking cothreads into account. This would be quite useful in visualizing the scheduling mechanism. Minor changes to various debug messages. Also sitting in gstdebug.h is a prototypical DEBUG_ENTER that's capable of performing DEBUG_LEAVE automatically. It does this by utilizing a little-known GCC extension that allows one to call a function with the same parameters as the current function. The macro uses this to basically call itself. A boolean is used to ensure that when it calls itself it actually runs the body of the function. In the meantime it prints stuff out before and after the real function, as well as constructing a debugging string. This can be used eventually to provide call-wide data on the DEBUG lines, instead of having to replicate data on each call to DEBUG. More research is needed into how this would most cleanly be fit into some other chunk of code, like GStreamer (I think of this DEBUG trick as a separate project, sorta). Unfortunately, the aforementioned DEBUG trick interacts quite poorly with cothreads. Almost any time it's used in a function that has anything remotely to do with a cothread context (as in, it runs in one), a segfault results from the __builtin_apply call, which is the heart of the whole thing. If someone who really knows assembly could analyze the resulting code to see what's really going on, we might find a way to fix either the macro or the cothreads (I'm thinking that there's something we missed in constructing the cothreads themselves) so this works in all cases. In the meantime, please insert both DEBUG_ENTER and DEBUG_LEAVE in your functions. Be sure to put DEBUG_ENTER after your variable declarations and before any functional code, not to put the function name in any DEBUG strings (it's already there, trust me), and put a DEBUG_LEAVE if you care enough. Changes are going to happen in the way DEBUGs and other printouts occur, so stay tuned.
2000-12-04 09:35:08 +00:00
/* we make too much noise for normal debugging... */
//#define GST_DEBUG_FORCE_DISABLE
#include "gst_private.h"
Changes made to the DEBUG system. New header file gstdebug.h holds the stuff to keep it out of gst.h's hair. DEBUG ... Original commit message from CVS: Changes made to the DEBUG system. New header file gstdebug.h holds the stuff to keep it out of gst.h's hair. DEBUG prints out the process id, cothread id, source filename and line number. Two new macros DEBUG_ENTER and DEBUG_LEAVE are used to show the entry and exit of a given function. This eventually might be used to construct call trace graphs, even taking cothreads into account. This would be quite useful in visualizing the scheduling mechanism. Minor changes to various debug messages. Also sitting in gstdebug.h is a prototypical DEBUG_ENTER that's capable of performing DEBUG_LEAVE automatically. It does this by utilizing a little-known GCC extension that allows one to call a function with the same parameters as the current function. The macro uses this to basically call itself. A boolean is used to ensure that when it calls itself it actually runs the body of the function. In the meantime it prints stuff out before and after the real function, as well as constructing a debugging string. This can be used eventually to provide call-wide data on the DEBUG lines, instead of having to replicate data on each call to DEBUG. More research is needed into how this would most cleanly be fit into some other chunk of code, like GStreamer (I think of this DEBUG trick as a separate project, sorta). Unfortunately, the aforementioned DEBUG trick interacts quite poorly with cothreads. Almost any time it's used in a function that has anything remotely to do with a cothread context (as in, it runs in one), a segfault results from the __builtin_apply call, which is the heart of the whole thing. If someone who really knows assembly could analyze the resulting code to see what's really going on, we might find a way to fix either the macro or the cothreads (I'm thinking that there's something we missed in constructing the cothreads themselves) so this works in all cases. In the meantime, please insert both DEBUG_ENTER and DEBUG_LEAVE in your functions. Be sure to put DEBUG_ENTER after your variable declarations and before any functional code, not to put the function name in any DEBUG strings (it's already there, trust me), and put a DEBUG_LEAVE if you care enough. Changes are going to happen in the way DEBUGs and other printouts occur, so stay tuned.
2000-12-04 09:35:08 +00:00
#include "cothreads.h"
#include "gstarch.h"
pthread_key_t _cothread_key = -1;
/* Disablig this define allows you to shut off a few checks in
* cothread_switch. This likely will speed things up fractionally */
#define COTHREAD_PARANOID
/**
* cothread_init:
*
* Create and initialize a new cothread context
*
* Returns: the new cothread context
*/
cothread_context*
cothread_init (void)
{
cothread_context *ctx = (cothread_context *)malloc(sizeof(cothread_context));
// we consider the initiating process to be cothread 0
ctx->nthreads = 1;
ctx->current = 0;
ctx->data = g_hash_table_new(g_str_hash, g_str_equal);
GST_INFO (GST_CAT_COTHREADS,"initializing cothreads");
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 = (int *)CURRENT_STACK_FRAME;
ctx->threads[0]->pc = 0;
// initialize the lock
#ifdef COTHREAD_ATOMIC
atomic_set (&ctx->threads[0]->lock, 0);
#else
ctx->threads[0]->lock = g_mutex_new();
#endif
GST_INFO (GST_CAT_COTHREADS,"0th thread is %p at sp:%p",ctx->threads[0], ctx->threads[0]->sp);
return ctx;
}
/**
* cothread_create:
* @ctx: the cothread context
*
* Create a new cothread state in the given context
*
* Returns: the new cothread state
*/
cothread_state*
cothread_create (cothread_context *ctx)
{
cothread_state *s;
GST_DEBUG (0,"pthread_self() %ld\n",pthread_self());
//if (0) {
if (pthread_self() == 0) { // FIXME uh, what does this test really do?
s = (cothread_state *)malloc(sizeof(int) * COTHREAD_STACKSIZE);
GST_DEBUG (0,"new stack (case 1) at %p\n",s);
} 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));
GST_DEBUG (0,"new stack (case 2) at %p\n",s);
if (mmap((char *)s,COTHREAD_STACKSIZE*(sizeof(int)),
PROT_READ|PROT_WRITE|PROT_EXEC,MAP_FIXED|MAP_PRIVATE|MAP_ANON,
-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);
// is this needed anymore?
s->top_sp = s->sp;
// initialize the lock
#ifdef COTHREAD_ATOMIC
atomic_set (s->lock, 0);
#else
s->lock = g_mutex_new();
#endif
GST_INFO (GST_CAT_COTHREADS,"created cothread #%d: %p at sp:%p", ctx->nthreads, s, s->sp);
ctx->threads[ctx->nthreads++] = s;
return s;
}
/**
* cothread_setfunc:
* @thread: the cothread state
* @func: the function to call
* @argc: argument count for the cothread function
* @argv: arguments for the cothread function
*
* Set the cothread function
*/
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_main:
* @ctx: cothread context to find main thread of
*
* Returns: the #cothread_state of the main (0th) thread
*/
cothread_state*
cothread_main(cothread_context *ctx)
{
GST_DEBUG (0,"returning %p, the 0th cothread\n",ctx->threads[0]);
return ctx->threads[0];
}
/**
* cothread_current)main:
*
* Returns: the #cothread_state of the main (0th) thread in the current pthread
*/
cothread_state*
cothread_current_main(void)
{
cothread_context *ctx = pthread_getspecific(_cothread_key);
return ctx->threads[0];
}
static void
cothread_stub (void)
{
cothread_context *ctx = pthread_getspecific(_cothread_key);
register cothread_state *thread = ctx->threads[ctx->current];
GST_DEBUG_ENTER("");
thread->flags |= COTHREAD_STARTED;
//#ifdef COTHREAD_ATOMIC
// // do something here to lock
//#else
// g_mutex_lock(thread->lock);
//#endif
while (1) {
thread->func(thread->argc,thread->argv);
// we do this to avoid ever returning, we just switch to 0th thread
cothread_switch(cothread_main(ctx));
}
thread->flags &= ~COTHREAD_STARTED;
thread->pc = 0;
thread->sp = thread->top_sp;
fprintf(stderr,"uh, yeah, we shouldn't be here, but we should deal anyway\n");
GST_DEBUG_LEAVE("");
}
/**
* cothread_getcurrent:
*
* Returns: the current cothread id
*/
int cothread_getcurrent(void) {
cothread_context *ctx = pthread_getspecific(_cothread_key);
if (!ctx) return -1;
return ctx->current;
}
/**
* cothread_set_data:
* @thread: the cothread state
* @key: a key for the data
* @data: the data
*
* adds data to a cothread
*/
void
cothread_set_data (cothread_state *thread,
gchar *key,
gpointer data)
{
cothread_context *ctx = pthread_getspecific(_cothread_key);
g_hash_table_insert(ctx->data, key, data);
}
/**
* cothread_get_data:
* @thread: the cothread state
* @key: a key for the data
*
* get data from the cothread
*
* Returns: the data assiciated with the key
*/
gpointer
cothread_get_data (cothread_state *thread,
gchar *key)
{
cothread_context *ctx = pthread_getspecific(_cothread_key);
return g_hash_table_lookup(ctx->data, key);
}
/**
* cothread_switch:
* @thread: cothread state to switch to
*
* Switches to the given cothread state
*/
void
cothread_switch (cothread_state *thread)
{
cothread_context *ctx;
cothread_state *current;
int enter;
#ifdef COTHREAD_PARANOID
if (thread == NULL) goto nothread;
#endif
ctx = thread->ctx;
#ifdef COTHREAD_PARANOID
if (ctx == NULL) goto nocontext;
#endif
current = ctx->threads[ctx->current];
#ifdef COTHREAD_PARANOID
if (current == NULL) goto nocurrent;
#endif
if (current == thread) goto selfswitch;
// unlock the current thread, we're out of that context now
#ifdef COTHREAD_ATOMIC
// do something to unlock the cothread
#else
g_mutex_unlock(current->lock);
#endif
// lock the next cothread before we even switch to it
#ifdef COTHREAD_ATOMIC
// do something to lock the cothread
#else
g_mutex_lock(thread->lock);
#endif
// find the number of the thread to switch to
GST_INFO (GST_CAT_COTHREAD_SWITCH,"switching from cothread #%d to cothread #%d",
ctx->current,thread->threadnum);
ctx->current = thread->threadnum;
/* save the current stack pointer, frame pointer, and pc */
#ifdef GST_ARCH_PRESETJMP
GST_ARCH_PRESETJMP();
#endif
enter = setjmp(current->jmp);
if (enter != 0) {
GST_DEBUG (0,"enter thread #%d %d %p<->%p (%d)\n",current->threadnum, enter,
current->sp, current->top_sp, current->top_sp-current->sp);
return;
}
GST_DEBUG (0,"exit thread #%d %d %p<->%p (%d)\n",current->threadnum, enter,
current->sp, current->top_sp, current->top_sp-current->sp);
enter = 1;
GST_DEBUG (0,"set stack to %p\n", thread->sp);
/* restore stack pointer and other stuff of new cothread */
if (thread->flags & COTHREAD_STARTED) {
GST_DEBUG (0,"in thread \n");
// switch to it
longjmp(thread->jmp,1);
} else {
GST_ARCH_SETUP_STACK(thread->sp);
GST_ARCH_SET_SP(thread->sp);
// start it
GST_ARCH_CALL(cothread_stub);
GST_DEBUG (0,"exit thread \n");
ctx->current = 0;
}
return;
#ifdef COTHREAD_PARANOID
nothread:
g_print("cothread: can't switch to NULL cothread!\n");
return;
nocontext:
g_print("cothread: there's no context, help!\n");
exit(2);
nocurrent:
g_print("cothread: there's no current thread, help!\n");
exit(2);
#endif /* COTHREAD_PARANOID */
selfswitch:
g_print("cothread: trying to switch to same thread, legal but not necessary\n");
return;
}
void
cothread_lock (cothread_state *thread)
{
#ifdef COTHREAD_ATOMIC
// do something to lock the cothread
#else
g_mutex_lock(thread->lock);
#endif
}
gboolean
cothread_trylock (cothread_state *thread)
{
#ifdef COTHREAD_ATOMIC
// do something to try to lock the cothread
#else
return g_mutex_trylock(thread->lock);
#endif
}
void
cothread_unlock (cothread_state *thread)
{
#ifdef COTHREAD_ATOMIC
// do something to unlock the cothread
#else
g_mutex_unlock(thread->lock);
#endif
}