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"
17 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(xbt_ctx, xbt, "Context");
19 #define VOIRP(expr) DEBUG1(" {" #expr " = %p }", expr)
21 static xbt_context_t current_context = NULL;
22 static xbt_context_t init_context = NULL;
23 static xbt_swag_t context_to_destroy = NULL;
24 static xbt_swag_t context_living = NULL;
26 #ifndef USE_PTHREADS /* USE_PTHREADS and USE_CONTEXT are exclusive */
28 /* don't want to play with conditional compilation in automake tonight, sorry.
29 include directly the c file from here when needed. */
30 # include "context_win32.c"
31 # define USE_WIN_CONTEXT
35 static void __xbt_context_yield(xbt_context_t context)
37 xbt_assert0(current_context,"You have to call context_init() first.");
39 DEBUG2("--------- current_context (%p) is yielding to context(%p) ---------",
40 current_context,context);
44 xbt_context_t self = current_context;
45 DEBUG0("**** Locking ****");
46 pthread_mutex_lock(&(context->mutex));
47 DEBUG0("**** Updating current_context ****");
48 current_context = context;
49 DEBUG0("**** Releasing the prisonner ****");
50 pthread_cond_signal(&(context->cond));
51 DEBUG0("**** Going to jail ****");
52 pthread_cond_wait(&(context->cond), &(context->mutex));
53 DEBUG0("**** Unlocking ****");
54 pthread_mutex_unlock(&(context->mutex));
55 DEBUG0("**** Updating current_context ****");
56 current_context = self;
60 VOIRP(current_context->save);
63 if(context) VOIRP(context->save);
68 if(context->save==NULL) {
69 DEBUG0("**** Yielding to somebody else ****");
70 DEBUG2("Saving current_context value (%p) to context(%p)->save",current_context,context);
71 context->save = current_context ;
72 DEBUG1("current_context becomes context(%p) ",context);
73 current_context = context ;
74 DEBUG1("Current position memorized (context->save). Jumping to context (%p)",context);
75 return_value = swapcontext (&(context->save->uc), &(context->uc));
76 xbt_assert0((return_value==0),"Context swapping failure");
77 DEBUG1("I am (%p). Coming back\n",context);
79 xbt_context_t old_context = context->save ;
80 DEBUG0("**** Back ! ****");
81 DEBUG2("Setting current_context (%p) to context(%p)->save",current_context,context);
82 current_context = context->save ;
83 DEBUG1("Setting context(%p)->save to NULL",context);
84 context->save = NULL ;
85 DEBUG2("Current position memorized (%p). Jumping to context (%p)",context,old_context);
86 return_value = swapcontext (&(context->uc), &(old_context->uc));
87 xbt_assert0((return_value==0),"Context swapping failure");
88 DEBUG1("I am (%p). Coming back\n",context);
95 static void xbt_context_destroy(xbt_context_t context)
98 xbt_free(context->thread);
99 pthread_mutex_destroy(&(context->mutex));
100 pthread_cond_destroy(&(context->cond));
102 if(context->exception) free(context->exception);
104 #ifdef USE_WIN_CONTEXT
105 if(context->uc.uc_stack.ss_sp)
106 free (context->uc.uc_stack.ss_sp);
113 static void __context_exit(xbt_context_t context ,int value)
116 DEBUG0("Freeing arguments");
117 for(i=0;i<context->argc; i++)
118 if(context->argv[i]) free(context->argv[i]);
119 if(context->argv) free(context->argv);
121 if(context->cleanup_func) {
122 DEBUG0("Calling cleanup function");
123 context->cleanup_func(context->cleanup_arg);
126 DEBUG0("Putting context in the to_destroy set");
127 xbt_swag_remove(context, context_living);
128 xbt_swag_insert(context, context_to_destroy);
129 DEBUG0("Context put in the to_destroy set");
133 DEBUG0("**** Locking ****");
134 pthread_mutex_lock(&(context->mutex));
135 DEBUG0("**** Updating current_context ****");
136 current_context = context;
137 DEBUG0("**** Releasing the prisonner ****");
138 pthread_cond_signal(&(context->cond));
139 DEBUG0("**** Unlocking ****");
140 pthread_mutex_unlock(&(context->mutex));
141 DEBUG0("**** Exiting ****");
144 __xbt_context_yield(context);
146 xbt_assert0(0,"You can't be here!");
149 static void *__context_wrapper(void *c)
151 xbt_context_t context = c;
154 DEBUG2("**[%p:%p]** Lock ****",context,(void*)pthread_self());
155 pthread_mutex_lock(&(context->mutex));
156 DEBUG2("**[%p:%p]** Releasing the prisonner ****",context,(void*)pthread_self());
157 pthread_cond_signal(&(context->cond));
158 DEBUG2("**[%p:%p]** Going to Jail ****",context,(void*)pthread_self());
159 pthread_cond_wait(&(context->cond), &(context->mutex));
160 DEBUG2("**[%p:%p]** Unlocking ****",context,(void*)pthread_self());
161 pthread_mutex_unlock(&(context->mutex));
164 if(context->startup_func)
165 context->startup_func(context->startup_arg);
167 DEBUG0("Calling the main function");
169 __context_exit(context, (context->code) (context->argc,context->argv));
173 /* callback: context fetching */
174 static ex_ctx_t *__context_ex_ctx(void)
176 return current_context->exception;
179 /* callback: termination */
180 static void __context_ex_terminate(xbt_ex_t *e) {
184 /* FIXME: there should be a configuration variable to choose this
185 if(current_context!=init_context)
186 __context_exit(current_context, e->value);
193 * \ingroup XBT_context
196 /** Context module initialization
198 * \warning It has to be called before using any other function of this module.
200 void xbt_context_init(void)
202 if(!current_context) {
203 current_context = init_context = xbt_new0(s_xbt_context_t,1);
204 init_context->exception = xbt_new(ex_ctx_t,1);
205 XBT_CTX_INITIALIZE(init_context->exception);
206 __xbt_ex_ctx = __context_ex_ctx;
207 __xbt_ex_terminate = __context_ex_terminate;
208 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
209 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
210 xbt_swag_insert(init_context, context_living);
214 /** Garbage collection
216 * Should be called some time to time to free the memory allocated for contexts
217 * that have finished executing their main functions.
219 void xbt_context_empty_trash(void)
221 xbt_context_t context=NULL;
223 while((context=xbt_swag_extract(context_to_destroy)))
224 xbt_context_destroy(context);
228 * \param context the context to start
230 * Calling this function prepares \a context to be run. It will
231 however run effectively only when calling #xbt_context_schedule
233 void xbt_context_start(xbt_context_t context)
236 /* Launch the thread */
237 DEBUG1("**[%p]** Locking ****",context);
238 pthread_mutex_lock(&(context->mutex));
239 DEBUG1("**[%p]** Pthread create ****",context);
240 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
241 "Unable to create a thread.");
242 DEBUG2("**[%p]** Pthread created : %p ****",context,(void*)(*(context->thread)));
243 DEBUG1("**[%p]** Going to jail ****",context);
244 pthread_cond_wait(&(context->cond), &(context->mutex));
245 DEBUG1("**[%p]** Unlocking ****",context);
246 pthread_mutex_unlock(&(context->mutex));
248 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
255 * \param code a main function
256 * \param startup_func a function to call when running the context for
257 * the first time and just before the main function \a code
258 * \param startup_arg the argument passed to the previous function (\a startup_func)
259 * \param cleanup_func a function to call when running the context, just after
260 the termination of the main function \a code
261 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
262 * \param argc first argument of function \a code
263 * \param argv seconde argument of function \a code
265 xbt_context_t xbt_context_new(xbt_context_function_t code,
266 void_f_pvoid_t startup_func, void *startup_arg,
267 void_f_pvoid_t cleanup_func, void *cleanup_arg,
268 int argc, char *argv[])
270 xbt_context_t res = NULL;
272 res = xbt_new0(s_xbt_context_t,1);
276 res->thread = xbt_new0(pthread_t,1);
277 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
278 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
280 /* FIXME: strerror is not thread safe */
281 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
282 res->uc.uc_link = NULL;
283 /* res->uc.uc_link = &(current_context->uc); */
284 /* WARNING : when this context is over, the current_context (i.e. the
285 father), is awaken... Theorically, the wrapper should prevent using
287 # ifdef USE_WIN_CONTEXT
288 res->uc.uc_stack.ss_sp = xbt_malloc(STACK_SIZE);
289 res->uc.uc_stack.ss_size = STACK_SIZE ;
291 res->uc.uc_stack.ss_sp = pth_skaddr_makecontext(res->stack,STACK_SIZE);
292 res->uc.uc_stack.ss_size = pth_sksize_makecontext(res->stack,STACK_SIZE);
293 # endif /* USE_WIN_CONTEXT */
294 #endif /* USE_PTHREADS or not */
297 res->startup_func = startup_func;
298 res->startup_arg = startup_arg;
299 res->cleanup_func = cleanup_func;
300 res->cleanup_arg = cleanup_arg;
301 res->exception = xbt_new(ex_ctx_t,1);
302 XBT_CTX_INITIALIZE(res->exception);
304 xbt_swag_insert(res, context_living);
310 * Calling this function makes the current context yield. The context
311 * that scheduled it returns from xbt_context_schedule as if nothing
314 void xbt_context_yield(void)
316 __xbt_context_yield(current_context);
320 * \param context the winner
322 * Calling this function blocks the current context and schedule \a context.
323 * When \a context will call xbt_context_yield, it will return
324 * to this function as if nothing had happened.
326 void xbt_context_schedule(xbt_context_t context)
328 DEBUG1("Scheduling %p",context);
329 xbt_assert0((current_context==init_context),
330 "You are not supposed to run this function here!");
331 __xbt_context_yield(context);
335 * This function kill all existing context and free all the memory
336 * that has been allocated in this module.
338 void xbt_context_exit(void) {
339 xbt_context_t context=NULL;
341 xbt_context_empty_trash();
342 xbt_swag_free(context_to_destroy);
344 while((context=xbt_swag_extract(context_living)))
345 xbt_context_free(context);
347 xbt_swag_free(context_living);
349 init_context = current_context = NULL ;
353 * \param context poor victim
355 * This function simply kills \a context... scarry isn't it ?
357 void xbt_context_free(xbt_context_t context)
361 xbt_swag_remove(context, context_living);
362 for(i=0;i<context->argc; i++)
363 if(context->argv[i]) free(context->argv[i]);
364 if(context->argv) free(context->argv);
366 if(context->cleanup_func)
367 context->cleanup_func(context->cleanup_arg);
368 xbt_context_destroy(context);