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"
14 #include "xbt/error.h"
15 #include "xbt/dynar.h"
16 #include "gras_config.h"
18 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(context, 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"
35 static void __xbt_context_yield(xbt_context_t context)
39 xbt_assert0(current_context,"You have to call context_init() first.");
41 DEBUG2("--------- current_context (%p) is yielding to context(%p) ---------",
42 current_context,context);
46 xbt_context_t self = current_context;
47 DEBUG0("**** Locking ****");
48 pthread_mutex_lock(&(context->mutex));
49 DEBUG0("**** Updating current_context ****");
50 current_context = context;
51 DEBUG0("**** Releasing the prisonner ****");
52 pthread_cond_signal(&(context->cond));
53 DEBUG0("**** Going to jail ****");
54 pthread_cond_wait(&(context->cond), &(context->mutex));
55 DEBUG0("**** Unlocking ****");
56 pthread_mutex_unlock(&(context->mutex));
57 DEBUG0("**** Updating current_context ****");
58 current_context = self;
62 VOIRP(current_context->save);
65 if(context) VOIRP(context->save);
67 if(context->save==NULL) {
68 DEBUG0("**** Yielding to somebody else ****");
69 DEBUG2("Saving current_context value (%p) to context(%p)->save",current_context,context);
70 context->save = current_context ;
71 DEBUG1("current_context becomes context(%p) ",context);
72 current_context = context ;
73 DEBUG1("Current position memorized (context->save). Jumping to context (%p)",context);
74 return_value = swapcontext (&(context->save->uc), &(context->uc));
75 xbt_assert0((return_value==0),"Context swapping failure");
76 DEBUG1("I am (%p). Coming back\n",context);
78 xbt_context_t old_context = context->save ;
79 DEBUG0("**** Back ! ****");
80 DEBUG2("Setting current_context (%p) to context(%p)->save",current_context,context);
81 current_context = context->save ;
82 DEBUG1("Setting context(%p)->save to NULL",context);
83 context->save = NULL ;
84 DEBUG2("Current position memorized (%p). Jumping to context (%p)",context,old_context);
85 return_value = swapcontext (&(context->uc), &(old_context->uc));
86 xbt_assert0((return_value==0),"Context swapping failure");
87 DEBUG1("I am (%p). Coming back\n",context);
94 static void xbt_context_destroy(xbt_context_t context)
97 xbt_free(context->thread);
98 pthread_mutex_destroy(&(context->mutex));
99 pthread_cond_destroy(&(context->cond));
105 static void *__context_wrapper(void *c)
107 xbt_context_t context = c;
111 DEBUG0("**** Lock ****");
112 pthread_mutex_lock(&(context->mutex));
113 DEBUG0("**** Releasing the prisonner ****");
114 pthread_cond_signal(&(context->cond));
115 DEBUG0("**** Going to Jail ****");
116 pthread_cond_wait(&(context->cond), &(context->mutex));
117 DEBUG0("**** Unlocking ****");
118 pthread_mutex_unlock(&(context->mutex));
121 if(context->startup_func)
122 context->startup_func(context->startup_arg);
124 DEBUG0("Calling the main function");
125 (context->code) (context->argc,context->argv);
127 for(i=0;i<context->argc; i++)
128 if(context->argv[i]) free(context->argv[i]);
129 if(context->argv) free(context->argv);
131 if(context->cleanup_func)
132 context->cleanup_func(context->cleanup_arg);
134 xbt_swag_remove(context, context_living);
135 xbt_swag_insert(context, context_to_destroy);
137 __xbt_context_yield(context);
138 xbt_assert0(0,"You're cannot be here!");
143 * \ingroup XBT_context
146 /** Context module initialization
148 * \warning It has to be called before using any other function of this module.
150 void xbt_context_init(void)
152 if(!current_context) {
153 current_context = init_context = xbt_new0(s_xbt_context_t,1);
154 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
155 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
156 xbt_swag_insert(init_context, context_living);
160 /** Garbage collection
162 * Should be called some time to time to free the memory allocated for contexts
163 * that have finished executing their main functions.
165 void xbt_context_empty_trash(void)
167 xbt_context_t context=NULL;
169 while((context=xbt_swag_extract(context_to_destroy)))
170 xbt_context_destroy(context);
174 * \param context the context to start
176 * Calling this function prepares \a context to be run. It will
177 however run effectively only when calling #xbt_context_schedule
179 void xbt_context_start(xbt_context_t context)
182 /* Launch the thread */
183 DEBUG0("**** Locking ****");
184 pthread_mutex_lock(&(context->mutex));
185 DEBUG0("**** Pthread create ****");
186 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
187 "Unable to create a thread.");
188 DEBUG0("**** Going to jail ****");
189 pthread_cond_wait(&(context->cond), &(context->mutex));
190 DEBUG0("**** Unlocking ****");
191 pthread_mutex_unlock(&(context->mutex));
193 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
200 * \param code a main function
201 * \param startup_func a function to call when running the context for
202 * the first time and just before the main function \a code
203 * \param startup_arg the argument passed to the previous function (\a startup_func)
204 * \param cleanup_func a function to call when running the context, just after
205 the termination of the main function \a code
206 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
207 * \param argc first argument of function \a code
208 * \param argv seconde argument of function \a code
210 xbt_context_t xbt_context_new(xbt_context_function_t code,
211 void_f_pvoid_t startup_func, void *startup_arg,
212 void_f_pvoid_t cleanup_func, void *cleanup_arg,
213 int argc, char *argv[])
215 xbt_context_t res = NULL;
217 res = xbt_new0(s_xbt_context_t,1);
221 res->thread = xbt_new0(pthread_t,1);
222 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
223 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
225 /* FIXME: strerror is not thread safe */
226 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
227 res->uc.uc_link = NULL;
228 /* res->uc.uc_link = &(current_context->uc); */
229 /* WARNING : when this context is over, the current_context (i.e. the
230 father), is awaken... Theorically, the wrapper should prevent using
232 res->uc.uc_stack.ss_sp = res->stack;
233 res->uc.uc_stack.ss_size = STACK_SIZE;
237 res->startup_func = startup_func;
238 res->startup_arg = startup_arg;
239 res->cleanup_func = cleanup_func;
240 res->cleanup_arg = cleanup_arg;
242 xbt_swag_insert(res, context_living);
248 * Calling this function makes the current context yield. The context
249 * that scheduled it returns from xbt_context_schedule as if nothing
252 void xbt_context_yield(void)
254 __xbt_context_yield(current_context);
258 * \param context the winner
260 * Calling this function blocks the current context and schedule \a context.
261 * When \a context will call xbt_context_yield, it will return
262 * to this function as if nothing had happened.
264 void xbt_context_schedule(xbt_context_t context)
266 xbt_assert0((current_context==init_context),
267 "You are not supposed to run this function here!");
268 __xbt_context_yield(context);
272 * This function kill all existing context and free all the memory
273 * that has been allocated in this module.
275 void xbt_context_exit(void) {
276 xbt_context_t context=NULL;
278 xbt_context_empty_trash();
279 xbt_swag_free(context_to_destroy);
281 while((context=xbt_swag_extract(context_living)))
282 xbt_context_free(context);
284 xbt_swag_free(context_living);
286 init_context = current_context = NULL ;
290 * \param context poor victim
292 * This function simply kills \a context... scarry isn't it ?
294 void xbt_context_free(xbt_context_t context)
298 xbt_swag_remove(context, context_living);
299 for(i=0;i<context->argc; i++)
300 if(context->argv[i]) free(context->argv[i]);
301 if(context->argv) free(context->argv);
303 if(context->cleanup_func)
304 context->cleanup_func(context->cleanup_arg);
305 xbt_context_destroy(context);