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 */
28 # ifndef HAVE_UCONTEXT_H
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 pthread_mutex_lock(&(context->mutex));
48 current_context = context;
49 pthread_cond_signal(&(context->cond));
50 pthread_cond_wait(&(context->cond), &(context->mutex));
51 pthread_mutex_unlock(&(context->mutex));
52 current_context = self;
56 VOIRP(current_context->save);
59 if(context) VOIRP(context->save);
61 if(context->save==NULL) {
62 DEBUG0("**** Yielding to somebody else ****");
63 DEBUG2("Saving current_context value (%p) to context(%p)->save",current_context,context);
64 context->save = current_context ;
65 DEBUG1("current_context becomes context(%p) ",context);
66 current_context = context ;
67 DEBUG1("Current position memorized (context->save). Jumping to context (%p)",context);
68 return_value = swapcontext (&(context->save->uc), &(context->uc));
69 xbt_assert0((return_value==0),"Context swapping failure");
70 DEBUG1("I am (%p). Coming back\n",context);
72 xbt_context_t old_context = context->save ;
73 DEBUG0("**** Back ! ****");
74 DEBUG2("Setting current_context (%p) to context(%p)->save",current_context,context);
75 current_context = context->save ;
76 DEBUG1("Setting context(%p)->save to NULL",context);
77 context->save = NULL ;
78 DEBUG2("Current position memorized (%p). Jumping to context (%p)",context,old_context);
79 return_value = swapcontext (&(context->uc), &(old_context->uc));
80 xbt_assert0((return_value==0),"Context swapping failure");
81 DEBUG1("I am (%p). Coming back\n",context);
88 static void xbt_context_destroy(xbt_context_t context)
91 xbt_free(context->thread);
92 pthread_mutex_destroy(&(context->mutex));
93 pthread_cond_destroy(&(context->cond));
99 static void *__context_wrapper(void *c)
101 xbt_context_t context = c;
105 pthread_cond_wait(&(context->cond), &(context->mutex));
106 pthread_mutex_unlock(&(context->mutex));
109 if(context->startup_func)
110 context->startup_func(context->startup_arg);
112 DEBUG0("Calling the main function");
113 (context->code) (context->argc,context->argv);
115 for(i=0;i<context->argc; i++)
116 if(context->argv[i]) free(context->argv[i]);
117 if(context->argv) free(context->argv);
119 if(context->cleanup_func)
120 context->cleanup_func(context->cleanup_arg);
122 xbt_swag_remove(context, context_living);
123 xbt_swag_insert(context, context_to_destroy);
125 __xbt_context_yield(context);
126 xbt_assert0(0,"You're cannot be here!");
131 * \ingroup XBT_context
134 /** Context module initialization
136 * \warning It has to be called before using any other function of this module.
138 void xbt_context_init(void)
140 if(!current_context) {
141 current_context = init_context = xbt_new0(s_xbt_context_t,1);
142 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
143 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
144 xbt_swag_insert(init_context, context_living);
148 /** Garbage collection
150 * Should be called some time to time to free the memory allocated for contexts
151 * that have finished executing their main functions.
153 void xbt_context_empty_trash(void)
155 xbt_context_t context=NULL;
157 while((context=xbt_swag_extract(context_to_destroy)))
158 xbt_context_destroy(context);
162 * \param context the context to start
164 * Calling this function prepares \a context to be run. It will
165 however run effectively only when calling #xbt_context_schedule
167 void xbt_context_start(xbt_context_t context)
170 pthread_mutex_lock(&(context->mutex));
172 /* Launch the thread */
173 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
174 "Unable to create a thread.");
176 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
183 * \param code a main function
184 * \param startup_func a function to call when running the context for
185 * the first time and just before the main function \a code
186 * \param startup_arg the argument passed to the previous function (\a startup_func)
187 * \param cleanup_func a function to call when running the context, just after
188 the termination of the main function \a code
189 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
190 * \param argc first argument of function \a code
191 * \param argv seconde argument of function \a code
193 xbt_context_t xbt_context_new(xbt_context_function_t code,
194 void_f_pvoid_t startup_func, void *startup_arg,
195 void_f_pvoid_t cleanup_func, void *cleanup_arg,
196 int argc, char *argv[])
198 xbt_context_t res = NULL;
200 res = xbt_new0(s_xbt_context_t,1);
204 res->thread = xbt_new0(pthread_t,1);
205 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
206 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
208 /* FIXME: strerror is not thread safe */
209 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
210 res->uc.uc_link = NULL;
211 /* res->uc.uc_link = &(current_context->uc); */
212 /* WARNING : when this context is over, the current_context (i.e. the
213 father), is awaken... Theorically, the wrapper should prevent using
215 res->uc.uc_stack.ss_sp = res->stack;
216 res->uc.uc_stack.ss_size = STACK_SIZE;
220 res->startup_func = startup_func;
221 res->startup_arg = startup_arg;
222 res->cleanup_func = cleanup_func;
223 res->cleanup_arg = cleanup_arg;
225 xbt_swag_insert(res, context_living);
231 * Calling this function makes the current context yield. The context
232 * that scheduled it returns from xbt_context_schedule as if nothing
235 void xbt_context_yield(void)
237 __xbt_context_yield(current_context);
241 * \param context the winner
243 * Calling this function blocks the current context and schedule \a context.
244 * When \a context will call xbt_context_yield, it will return
245 * to this function as if nothing had happened.
247 void xbt_context_schedule(xbt_context_t context)
249 xbt_assert0((current_context==init_context),
250 "You are not supposed to run this function here!");
251 __xbt_context_yield(context);
255 * This function kill all existing context and free all the memory
256 * that has been allocated in this module.
258 void xbt_context_exit(void) {
259 xbt_context_t context=NULL;
261 xbt_context_empty_trash();
262 xbt_swag_free(context_to_destroy);
264 while((context=xbt_swag_extract(context_living)))
265 xbt_context_free(context);
267 xbt_swag_free(context_living);
269 init_context = current_context = NULL ;
273 * \param context poor victim
275 * This function simply kills \a context... scarry isn't it ?
277 void xbt_context_free(xbt_context_t context)
281 xbt_swag_remove(context, context_living);
282 for(i=0;i<context->argc; i++)
283 if(context->argv[i]) free(context->argv[i]);
284 if(context->argv) free(context->argv);
286 if(context->cleanup_func)
287 context->cleanup_func(context->cleanup_arg);
288 xbt_context_destroy(context);