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 "gras_config.h"
18 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(xbt_ctx, xbt, "Context");
20 #define VOIRP(expr) DEBUG1(" {" #expr " = %p }", expr)
22 static xbt_context_t current_context = NULL;
23 static xbt_context_t init_context = NULL;
24 static xbt_swag_t context_to_destroy = NULL;
25 static xbt_swag_t context_living = NULL;
27 #ifndef USE_PTHREADS /* USE_PTHREADS and USE_CONTEXT are exclusive */
29 /* don't want to play with conditional compilation in automake tonight, sorry.
30 include directly the c file from here when needed. */
31 # include "context_win32.c"
32 # define USE_WIN_CONTEXT
36 static void __xbt_context_yield(xbt_context_t context)
38 xbt_assert0(current_context,"You have to call context_init() first.");
40 DEBUG2("--------- current_context (%p) is yielding to context(%p) ---------",
41 current_context,context);
45 xbt_context_t self = current_context;
46 DEBUG0("**** Locking ****");
47 pthread_mutex_lock(&(context->mutex));
48 DEBUG0("**** Updating current_context ****");
49 current_context = context;
50 DEBUG0("**** Releasing the prisonner ****");
51 pthread_cond_signal(&(context->cond));
52 DEBUG0("**** Going to jail ****");
53 pthread_cond_wait(&(context->cond), &(context->mutex));
54 DEBUG0("**** Unlocking ****");
55 pthread_mutex_unlock(&(context->mutex));
56 DEBUG0("**** Updating current_context ****");
57 current_context = self;
61 VOIRP(current_context->save);
64 if(context) VOIRP(context->save);
69 if(context->save==NULL) {
70 DEBUG0("**** Yielding to somebody else ****");
71 DEBUG2("Saving current_context value (%p) to context(%p)->save",current_context,context);
72 context->save = current_context ;
73 DEBUG1("current_context becomes context(%p) ",context);
74 current_context = context ;
75 DEBUG1("Current position memorized (context->save). Jumping to context (%p)",context);
76 return_value = swapcontext (&(context->save->uc), &(context->uc));
77 xbt_assert0((return_value==0),"Context swapping failure");
78 DEBUG1("I am (%p). Coming back\n",context);
80 xbt_context_t old_context = context->save ;
81 DEBUG0("**** Back ! ****");
82 DEBUG2("Setting current_context (%p) to context(%p)->save",current_context,context);
83 current_context = context->save ;
84 DEBUG1("Setting context(%p)->save to NULL",context);
85 context->save = NULL ;
86 DEBUG2("Current position memorized (%p). Jumping to context (%p)",context,old_context);
87 return_value = swapcontext (&(context->uc), &(old_context->uc));
88 xbt_assert0((return_value==0),"Context swapping failure");
89 DEBUG1("I am (%p). Coming back\n",context);
96 static void xbt_context_destroy(xbt_context_t context)
99 xbt_free(context->thread);
100 pthread_mutex_destroy(&(context->mutex));
101 pthread_cond_destroy(&(context->cond));
103 if(context->exception) free(context->exception);
108 static void __context_exit(xbt_context_t context ,int value)
111 DEBUG0("Freeing arguments");
112 for(i=0;i<context->argc; i++)
113 if(context->argv[i]) free(context->argv[i]);
114 if(context->argv) free(context->argv);
116 if(context->cleanup_func) {
117 DEBUG0("Calling cleanup function");
118 context->cleanup_func(context->cleanup_arg);
121 DEBUG0("Putting context in the to_destroy set");
122 xbt_swag_remove(context, context_living);
123 xbt_swag_insert(context, context_to_destroy);
124 DEBUG0("Context put in the to_destroy set");
128 DEBUG0("**** Locking ****");
129 pthread_mutex_lock(&(context->mutex));
130 DEBUG0("**** Updating current_context ****");
131 current_context = context;
132 DEBUG0("**** Releasing the prisonner ****");
133 pthread_cond_signal(&(context->cond));
134 DEBUG0("**** Unlocking ****");
135 pthread_mutex_unlock(&(context->mutex));
136 DEBUG0("**** Exiting ****");
139 __xbt_context_yield(context);
141 xbt_assert0(0,"You can't be here!");
144 static void *__context_wrapper(void *c)
146 xbt_context_t context = c;
149 DEBUG2("**[%p:%p]** Lock ****",context,(void*)pthread_self());
150 pthread_mutex_lock(&(context->mutex));
151 DEBUG2("**[%p:%p]** Releasing the prisonner ****",context,(void*)pthread_self());
152 pthread_cond_signal(&(context->cond));
153 DEBUG2("**[%p:%p]** Going to Jail ****",context,(void*)pthread_self());
154 pthread_cond_wait(&(context->cond), &(context->mutex));
155 DEBUG2("**[%p:%p]** Unlocking ****",context,(void*)pthread_self());
156 pthread_mutex_unlock(&(context->mutex));
159 if(context->startup_func)
160 context->startup_func(context->startup_arg);
162 DEBUG0("Calling the main function");
164 __context_exit(context, (context->code) (context->argc,context->argv));
168 /* callback: context fetching */
169 static ex_ctx_t *__context_ex_ctx(void)
171 return current_context->exception;
174 /* callback: termination */
175 static void __context_ex_terminate(xbt_ex_t *e) {
179 /* FIXME: there should be a configuration variable to choose this
180 if(current_context!=init_context)
181 __context_exit(current_context, e->value);
188 * \ingroup XBT_context
191 /** Context module initialization
193 * \warning It has to be called before using any other function of this module.
195 void xbt_context_init(void)
197 if(!current_context) {
198 current_context = init_context = xbt_new0(s_xbt_context_t,1);
199 init_context->exception = xbt_new(ex_ctx_t,1);
200 XBT_CTX_INITIALIZE(init_context->exception);
201 __xbt_ex_ctx = __context_ex_ctx;
202 __xbt_ex_terminate = __context_ex_terminate;
203 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
204 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
205 xbt_swag_insert(init_context, context_living);
209 /** Garbage collection
211 * Should be called some time to time to free the memory allocated for contexts
212 * that have finished executing their main functions.
214 void xbt_context_empty_trash(void)
216 xbt_context_t context=NULL;
218 while((context=xbt_swag_extract(context_to_destroy)))
219 xbt_context_destroy(context);
223 * \param context the context to start
225 * Calling this function prepares \a context to be run. It will
226 however run effectively only when calling #xbt_context_schedule
228 void xbt_context_start(xbt_context_t context)
231 /* Launch the thread */
232 DEBUG1("**[%p]** Locking ****",context);
233 pthread_mutex_lock(&(context->mutex));
234 DEBUG1("**[%p]** Pthread create ****",context);
235 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
236 "Unable to create a thread.");
237 DEBUG2("**[%p]** Pthread created : %p ****",context,(void*)(*(context->thread)));
238 DEBUG1("**[%p]** Going to jail ****",context);
239 pthread_cond_wait(&(context->cond), &(context->mutex));
240 DEBUG1("**[%p]** Unlocking ****",context);
241 pthread_mutex_unlock(&(context->mutex));
243 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
250 * \param code a main function
251 * \param startup_func a function to call when running the context for
252 * the first time and just before the main function \a code
253 * \param startup_arg the argument passed to the previous function (\a startup_func)
254 * \param cleanup_func a function to call when running the context, just after
255 the termination of the main function \a code
256 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
257 * \param argc first argument of function \a code
258 * \param argv seconde argument of function \a code
260 xbt_context_t xbt_context_new(xbt_context_function_t code,
261 void_f_pvoid_t startup_func, void *startup_arg,
262 void_f_pvoid_t cleanup_func, void *cleanup_arg,
263 int argc, char *argv[])
265 xbt_context_t res = NULL;
267 res = xbt_new0(s_xbt_context_t,1);
271 res->thread = xbt_new0(pthread_t,1);
272 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
273 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
275 /* FIXME: strerror is not thread safe */
276 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
277 res->uc.uc_link = NULL;
278 /* res->uc.uc_link = &(current_context->uc); */
279 /* WARNING : when this context is over, the current_context (i.e. the
280 father), is awaken... Theorically, the wrapper should prevent using
282 # ifndef USE_WIN_CONTEXT
283 res->uc.uc_stack.ss_sp = pth_skaddr_makecontext(res->stack,STACK_SIZE);
284 res->uc.uc_stack.ss_size = pth_sksize_makecontext(res->stack,STACK_SIZE);
285 # endif /* USE_WIN_CONTEXT */
286 #endif /* USE_PTHREADS or not */
289 res->startup_func = startup_func;
290 res->startup_arg = startup_arg;
291 res->cleanup_func = cleanup_func;
292 res->cleanup_arg = cleanup_arg;
293 res->exception = xbt_new(ex_ctx_t,1);
294 XBT_CTX_INITIALIZE(res->exception);
296 xbt_swag_insert(res, context_living);
302 * Calling this function makes the current context yield. The context
303 * that scheduled it returns from xbt_context_schedule as if nothing
306 void xbt_context_yield(void)
308 __xbt_context_yield(current_context);
312 * \param context the winner
314 * Calling this function blocks the current context and schedule \a context.
315 * When \a context will call xbt_context_yield, it will return
316 * to this function as if nothing had happened.
318 void xbt_context_schedule(xbt_context_t context)
320 DEBUG1("Scheduling %p",context);
321 xbt_assert0((current_context==init_context),
322 "You are not supposed to run this function here!");
323 __xbt_context_yield(context);
327 * This function kill all existing context and free all the memory
328 * that has been allocated in this module.
330 void xbt_context_exit(void) {
331 xbt_context_t context=NULL;
333 xbt_context_empty_trash();
334 xbt_swag_free(context_to_destroy);
336 while((context=xbt_swag_extract(context_living)))
337 xbt_context_free(context);
339 xbt_swag_free(context_living);
341 init_context = current_context = NULL ;
345 * \param context poor victim
347 * This function simply kills \a context... scarry isn't it ?
349 void xbt_context_free(xbt_context_t context)
353 xbt_swag_remove(context, context_living);
354 for(i=0;i<context->argc; i++)
355 if(context->argv[i]) free(context->argv[i]);
356 if(context->argv) free(context->argv);
358 if(context->cleanup_func)
359 context->cleanup_func(context->cleanup_arg);
360 xbt_context_destroy(context);