3 /* a fast and simple context switching library */
5 /* Copyright (c) 2004 Arnaud Legrand. */
6 /* Copyright (c) 2004, 2005 Martin Quinson. */
7 /* All rights reserved. */
9 /* This program is free software; you can redistribute it and/or modify it
10 * under the terms of the license (GNU LGPL) which comes with this package. */
13 #include "context_private.h"
15 #include "xbt/dynar.h"
16 #include "xbt/xbt_thread.h"
17 #include <pthread.h> // I need pthread_join that is not yet available in xbt_thread.
19 #ifdef CONTEXT_THREADS
20 /* This file (context.c) is only loaded in libsimgrid, not libgras.
21 * xbt_thread is only loaded in libgras explicitly, and we need it in
22 * libsimgrid, but only when it is the backend used to implement the
23 * xbt_context. So, do load it on need.
25 #include "xbt/xbt_thread.c"
28 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(xbt_ctx, xbt, "Context");
30 #define VOIRP(expr) DEBUG1(" {" #expr " = %p }", expr)
32 static xbt_context_t current_context = NULL;
33 static xbt_context_t init_context = NULL;
34 static xbt_swag_t context_to_destroy = NULL;
35 static xbt_swag_t context_living = NULL;
37 static void __context_exit(xbt_context_t context ,int value);
38 static void __xbt_context_yield(xbt_context_t context)
40 xbt_assert0(current_context,"You have to call context_init() first.");
42 DEBUG2("--------- current_context (%p) is yielding to context(%p) ---------",current_context,context);
44 #ifdef CONTEXT_THREADS
46 xbt_context_t self = current_context;
47 DEBUG1("[%p] **** Locking ****", self);
48 xbt_mutex_lock(context->mutex);
49 DEBUG1("[%p] **** Updating current_context ****", self);
50 current_context = context;
51 DEBUG1("[%p] **** Releasing the prisonner ****", self);
52 xbt_thcond_signal(context->cond);
53 DEBUG1("[%p] **** Going to jail ****", self);
54 xbt_thcond_wait(context->cond, context->mutex);
55 DEBUG1("[%p] **** Unlocking ****", self);
56 xbt_mutex_unlock(context->mutex);
57 DEBUG1("[%p] **** Updating current_context ****", self);
58 current_context = self;
60 #else /* use SUSv2 contexts */
62 VOIRP(current_context->save);
73 if(context->save==NULL){
75 DEBUG1("[%p] **** Yielding to somebody else ****", current_context);
76 DEBUG2("Saving current_context value (%p) to context(%p)->save",current_context,context);
77 context->save = current_context ;
78 DEBUG1("current_context becomes context(%p) ",context);
79 current_context = context ;
80 DEBUG1("Current position memorized (context->save). Jumping to context (%p)",context);
81 return_value = swapcontext (&(context->save->uc), &(context->uc));
82 xbt_assert0((return_value==0),"Context swapping failure");
83 DEBUG1("I am (%p). Coming back\n",context);
85 xbt_context_t old_context = context->save ;
86 DEBUG1("[%p] **** Back ! ****", context);
87 DEBUG2("Setting current_context (%p) to context(%p)->save",current_context,context);
88 current_context = context->save ;
89 DEBUG1("Setting context(%p)->save to NULL",context);
90 context->save = NULL ;
91 DEBUG2("Current position memorized (%p). Jumping to context (%p)",context,old_context);
92 return_value = swapcontext (&(context->uc), &(old_context->uc));
93 xbt_assert0((return_value==0),"Context swapping failure");
94 DEBUG1("I am (%p). Coming back\n",context);
99 if(current_context->iwannadie)
100 __context_exit(current_context, 1);
105 static void xbt_context_free(xbt_context_t context)
107 if (!context) return;
108 DEBUG1("Freeing %p",context);
109 #ifdef CONTEXT_THREADS
110 DEBUG1("\t joining %p",(void *)context->thread->t);
111 pthread_join(context->thread->t,NULL);
112 DEBUG1("\t xbt_free %p",(void *)context->thread);
113 xbt_free(context->thread);
114 DEBUG1("\t mutex_destroy %p",(void *)context->mutex);
115 xbt_mutex_destroy(context->mutex);
116 DEBUG1("\t cond_destroy %p",(void *)context->cond);
117 xbt_thcond_destroy(context->cond);
119 context->thread = NULL;
120 context->mutex = NULL;
121 context->cond = NULL;
124 if(context->exception)
125 free(context->exception);
131 static void __context_exit(xbt_context_t context ,int value)
135 DEBUG1("--------- %p is exiting ---------",context);
137 DEBUG0("Calling cleanup functions");
138 if(context->cleanup_func){
139 DEBUG0("Calling cleanup function");
140 context->cleanup_func(context->cleanup_arg);
143 DEBUG0("Freeing arguments");
144 for(i=0;i<context->argc; i++)
146 free(context->argv[i]);
151 DEBUG0("Putting context in the to_destroy set");
152 xbt_swag_remove(context, context_living);
153 xbt_swag_insert(context, context_to_destroy);
154 DEBUG0("Context put in the to_destroy set");
158 #ifdef CONTEXT_THREADS
159 DEBUG1("[%p] **** Locking ****", context);
160 xbt_mutex_lock(context->mutex);
161 /* DEBUG1("[%p] **** Updating current_context ****"); */
162 /* current_context = context; */
163 DEBUG1("[%p] **** Releasing the prisonner ****", context);
164 xbt_thcond_signal(context->cond);
165 DEBUG1("[%p] **** Unlocking ****", context);
166 xbt_mutex_unlock(context->mutex);
167 DEBUG1("[%p] **** Exiting ****", context);
168 xbt_thread_exit(NULL); // We should provide return value in case other wants it
170 __xbt_context_yield(context);
172 xbt_assert0(0,"You can't be here!");
176 __context_wrapper(void* c) {
177 xbt_context_t context = (xbt_context_t)c;
179 #ifdef CONTEXT_THREADS
180 context->thread = xbt_thread_self();
182 DEBUG2("**[%p:%p]** Lock ****",context,(void*)xbt_thread_self());
183 xbt_mutex_lock(context->mutex);
185 DEBUG2("**[%p:%p]** Releasing the prisonner ****",context,(void*)xbt_thread_self());
186 xbt_thcond_signal(context->cond);
188 DEBUG2("**[%p:%p]** Going to Jail ****",context,(void*)xbt_thread_self());
189 xbt_thcond_wait(context->cond, context->mutex);
191 DEBUG2("**[%p:%p]** Unlocking ****",context,(void*)xbt_thread_self());
192 xbt_mutex_unlock(context->mutex);
196 if(context->startup_func)
197 context->startup_func(context->startup_arg);
199 DEBUG0("Calling the main function");
201 __context_exit(context, (context->code) (context->argc,context->argv));
205 /* callback: context fetching */
206 static ex_ctx_t *__context_ex_ctx(void)
208 return current_context->exception;
211 /* callback: termination */
212 static void __context_ex_terminate(xbt_ex_t *e) {
216 /* FIXME: there should be a configuration variable to choose this
217 if(current_context!=init_context)
218 __context_exit(current_context, e->value);
225 * \ingroup XBT_context
228 /** Context module initialization
230 * \warning It has to be called before using any other function of this module.
232 void xbt_context_init(void)
234 if(!current_context){
235 current_context = init_context = xbt_new0(s_xbt_context_t,1);
236 DEBUG1("Init Context (%p)",init_context);
238 init_context->exception = xbt_new(ex_ctx_t,1);
239 XBT_CTX_INITIALIZE(init_context->exception);
240 __xbt_ex_ctx = __context_ex_ctx;
241 __xbt_ex_terminate = __context_ex_terminate;
242 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
243 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
244 xbt_swag_insert(init_context, context_living);
248 /** Garbage collection
250 * Should be called some time to time to free the memory allocated for contexts
251 * that have finished executing their main functions.
253 void xbt_context_empty_trash(void)
255 xbt_context_t context=NULL;
256 DEBUG1("Emptying trashbin (%d contexts to free)",
257 xbt_swag_size(context_to_destroy));
258 while((context=xbt_swag_extract(context_to_destroy)))
259 xbt_context_free(context);
263 * \param context the context to start
265 * Calling this function prepares \a context to be run. It will
266 however run effectively only when calling #xbt_context_schedule
268 void xbt_context_start(xbt_context_t context)
270 #ifdef CONTEXT_THREADS
271 /* Launch the thread */
272 DEBUG1("**[%p]** Locking ****",context);
273 xbt_mutex_lock(context->mutex);
275 DEBUG1("**[%p]** Thread create ****",context);
276 context->thread = xbt_thread_create(__context_wrapper, context);
277 DEBUG2("**[%p]** Thread created : %p ****",context,context->thread);
279 DEBUG1("**[%p]** Going to jail ****",context);
280 xbt_thcond_wait(context->cond, context->mutex);
281 DEBUG1("**[%p]** Unlocking ****",context);
282 xbt_mutex_unlock(context->mutex);
284 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,1, context);
290 * \param code a main function
291 * \param startup_func a function to call when running the context for
292 * the first time and just before the main function \a code
293 * \param startup_arg the argument passed to the previous function (\a startup_func)
294 * \param cleanup_func a function to call when running the context, just after
295 the termination of the main function \a code
296 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
297 * \param argc first argument of function \a code
298 * \param argv seconde argument of function \a code
300 xbt_context_t xbt_context_new(xbt_context_function_t code,
301 void_f_pvoid_t startup_func, void *startup_arg,
302 void_f_pvoid_t cleanup_func, void *cleanup_arg,
303 int argc, char *argv[])
305 xbt_context_t res = NULL;
307 res = xbt_new0(s_xbt_context_t,1);
310 #ifdef CONTEXT_THREADS
311 res->mutex = xbt_mutex_init();
312 res->cond = xbt_thcond_init();
314 /* FIXME: strerror is not thread safe */
315 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
316 res->uc.uc_link = NULL;
317 /* res->uc.uc_link = &(current_context->uc); */
318 /* WARNING : when this context is over, the current_context (i.e. the
319 father), is awaken... Theorically, the wrapper should prevent using
321 res->uc.uc_stack.ss_sp = pth_skaddr_makecontext(res->stack,STACK_SIZE);
322 res->uc.uc_stack.ss_size = pth_sksize_makecontext(res->stack,STACK_SIZE);
323 #endif /* CONTEXT_THREADS or not */
327 res->startup_func = startup_func;
328 res->startup_arg = startup_arg;
329 res->cleanup_func = cleanup_func;
330 res->cleanup_arg = cleanup_arg;
331 res->exception = xbt_new(ex_ctx_t,1);
332 XBT_CTX_INITIALIZE(res->exception);
334 xbt_swag_insert(res, context_living);
340 * Calling this function makes the current context yield. The context
341 * that scheduled it returns from xbt_context_schedule as if nothing
344 void xbt_context_yield(void)
346 __xbt_context_yield(current_context);
350 * \param context the winner
352 * Calling this function blocks the current context and schedule \a context.
353 * When \a context will call xbt_context_yield, it will return
354 * to this function as if nothing had happened.
356 void xbt_context_schedule(xbt_context_t context)
358 DEBUG1("Scheduling %p",context);
359 xbt_assert0((current_context==init_context),"You are not supposed to run this function here!");
360 __xbt_context_yield(context);
364 * This function kill all existing context and free all the memory
365 * that has been allocated in this module.
367 void xbt_context_exit(void) {
368 xbt_context_t context=NULL;
370 xbt_context_empty_trash();
371 while((context=xbt_swag_extract(context_living))) {
372 if(context!=init_context) {
373 xbt_context_kill(context);
376 // xbt_context_kill(init_context);
378 xbt_context_empty_trash();
379 xbt_swag_free(context_to_destroy);
380 xbt_swag_free(context_living);
382 init_context = current_context = NULL ;
386 * \param context poor victim
388 * This function simply kills \a context... scarry isn't it ?
390 void xbt_context_kill(xbt_context_t context)
392 DEBUG1("Killing %p", context);
394 context->iwannadie=1;
395 DEBUG1("Scheduling %p",context);
396 __xbt_context_yield(context);
397 DEBUG1("End of Scheduling %p",context);