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"
32 # define USE_WIN_CONTEXT
36 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) ---------",
43 current_context,context);
47 xbt_context_t self = current_context;
48 DEBUG0("**** Locking ****");
49 pthread_mutex_lock(&(context->mutex));
50 DEBUG0("**** Updating current_context ****");
51 current_context = context;
52 DEBUG0("**** Releasing the prisonner ****");
53 pthread_cond_signal(&(context->cond));
54 DEBUG0("**** Going to jail ****");
55 pthread_cond_wait(&(context->cond), &(context->mutex));
56 DEBUG0("**** Unlocking ****");
57 pthread_mutex_unlock(&(context->mutex));
58 DEBUG0("**** Updating current_context ****");
59 current_context = self;
63 VOIRP(current_context->save);
66 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));
106 static void *__context_wrapper(void *c)
108 xbt_context_t context = c;
112 DEBUG0("**** Lock ****");
113 pthread_mutex_lock(&(context->mutex));
114 DEBUG0("**** Releasing the prisonner ****");
115 pthread_cond_signal(&(context->cond));
116 DEBUG0("**** Going to Jail ****");
117 pthread_cond_wait(&(context->cond), &(context->mutex));
118 DEBUG0("**** Unlocking ****");
119 pthread_mutex_unlock(&(context->mutex));
122 if(context->startup_func)
123 context->startup_func(context->startup_arg);
125 DEBUG0("Calling the main function");
126 (context->code) (context->argc,context->argv);
128 for(i=0;i<context->argc; i++)
129 if(context->argv[i]) free(context->argv[i]);
130 if(context->argv) free(context->argv);
132 if(context->cleanup_func)
133 context->cleanup_func(context->cleanup_arg);
135 xbt_swag_remove(context, context_living);
136 xbt_swag_insert(context, context_to_destroy);
138 __xbt_context_yield(context);
139 xbt_assert0(0,"You're cannot be here!");
144 * \ingroup XBT_context
147 /** Context module initialization
149 * \warning It has to be called before using any other function of this module.
151 void xbt_context_init(void)
153 if(!current_context) {
154 current_context = init_context = xbt_new0(s_xbt_context_t,1);
155 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
156 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
157 xbt_swag_insert(init_context, context_living);
161 /** Garbage collection
163 * Should be called some time to time to free the memory allocated for contexts
164 * that have finished executing their main functions.
166 void xbt_context_empty_trash(void)
168 xbt_context_t context=NULL;
170 while((context=xbt_swag_extract(context_to_destroy)))
171 xbt_context_destroy(context);
175 * \param context the context to start
177 * Calling this function prepares \a context to be run. It will
178 however run effectively only when calling #xbt_context_schedule
180 void xbt_context_start(xbt_context_t context)
183 /* Launch the thread */
184 DEBUG0("**** Locking ****");
185 pthread_mutex_lock(&(context->mutex));
186 DEBUG0("**** Pthread create ****");
187 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
188 "Unable to create a thread.");
189 DEBUG0("**** Going to jail ****");
190 pthread_cond_wait(&(context->cond), &(context->mutex));
191 DEBUG0("**** Unlocking ****");
192 pthread_mutex_unlock(&(context->mutex));
194 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
201 * \param code a main function
202 * \param startup_func a function to call when running the context for
203 * the first time and just before the main function \a code
204 * \param startup_arg the argument passed to the previous function (\a startup_func)
205 * \param cleanup_func a function to call when running the context, just after
206 the termination of the main function \a code
207 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
208 * \param argc first argument of function \a code
209 * \param argv seconde argument of function \a code
211 xbt_context_t xbt_context_new(xbt_context_function_t code,
212 void_f_pvoid_t startup_func, void *startup_arg,
213 void_f_pvoid_t cleanup_func, void *cleanup_arg,
214 int argc, char *argv[])
216 xbt_context_t res = NULL;
218 res = xbt_new0(s_xbt_context_t,1);
222 res->thread = xbt_new0(pthread_t,1);
223 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
224 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
226 /* FIXME: strerror is not thread safe */
227 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
228 res->uc.uc_link = NULL;
229 /* res->uc.uc_link = &(current_context->uc); */
230 /* WARNING : when this context is over, the current_context (i.e. the
231 father), is awaken... Theorically, the wrapper should prevent using
233 # ifndef USE_WIN_CONTEXT
234 res->uc.uc_stack.ss_sp = pth_skaddr_makecontext(res->stack,STACK_SIZE);
235 res->uc.uc_stack.ss_size = pth_sksize_makecontext(res->stack,STACK_SIZE);
236 # endif /* USE_WIN_CONTEXT */
237 #endif /* USE_PTHREADS or not */
240 res->startup_func = startup_func;
241 res->startup_arg = startup_arg;
242 res->cleanup_func = cleanup_func;
243 res->cleanup_arg = cleanup_arg;
245 xbt_swag_insert(res, context_living);
251 * Calling this function makes the current context yield. The context
252 * that scheduled it returns from xbt_context_schedule as if nothing
255 void xbt_context_yield(void)
257 __xbt_context_yield(current_context);
261 * \param context the winner
263 * Calling this function blocks the current context and schedule \a context.
264 * When \a context will call xbt_context_yield, it will return
265 * to this function as if nothing had happened.
267 void xbt_context_schedule(xbt_context_t context)
269 xbt_assert0((current_context==init_context),
270 "You are not supposed to run this function here!");
271 __xbt_context_yield(context);
275 * This function kill all existing context and free all the memory
276 * that has been allocated in this module.
278 void xbt_context_exit(void) {
279 xbt_context_t context=NULL;
281 xbt_context_empty_trash();
282 xbt_swag_free(context_to_destroy);
284 while((context=xbt_swag_extract(context_living)))
285 xbt_context_free(context);
287 xbt_swag_free(context_living);
289 init_context = current_context = NULL ;
293 * \param context poor victim
295 * This function simply kills \a context... scarry isn't it ?
297 void xbt_context_free(xbt_context_t context)
301 xbt_swag_remove(context, context_living);
302 for(i=0;i<context->argc; i++)
303 if(context->argv[i]) free(context->argv[i]);
304 if(context->argv) free(context->argv);
306 if(context->cleanup_func)
307 context->cleanup_func(context->cleanup_arg);
308 xbt_context_destroy(context);