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 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 pthread_mutex_lock(&(context->mutex));
112 pthread_cond_signal(&(context->cond));
113 pthread_cond_wait(&(context->cond), &(context->mutex));
114 pthread_mutex_unlock(&(context->mutex));
117 if(context->startup_func)
118 context->startup_func(context->startup_arg);
120 DEBUG0("Calling the main function");
121 (context->code) (context->argc,context->argv);
123 for(i=0;i<context->argc; i++)
124 if(context->argv[i]) free(context->argv[i]);
125 if(context->argv) free(context->argv);
127 if(context->cleanup_func)
128 context->cleanup_func(context->cleanup_arg);
130 xbt_swag_remove(context, context_living);
131 xbt_swag_insert(context, context_to_destroy);
133 __xbt_context_yield(context);
134 xbt_assert0(0,"You're cannot be here!");
139 * \ingroup XBT_context
142 /** Context module initialization
144 * \warning It has to be called before using any other function of this module.
146 void xbt_context_init(void)
148 if(!current_context) {
149 current_context = init_context = xbt_new0(s_xbt_context_t,1);
150 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
151 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
152 xbt_swag_insert(init_context, context_living);
156 /** Garbage collection
158 * Should be called some time to time to free the memory allocated for contexts
159 * that have finished executing their main functions.
161 void xbt_context_empty_trash(void)
163 xbt_context_t context=NULL;
165 while((context=xbt_swag_extract(context_to_destroy)))
166 xbt_context_destroy(context);
170 * \param context the context to start
172 * Calling this function prepares \a context to be run. It will
173 however run effectively only when calling #xbt_context_schedule
175 void xbt_context_start(xbt_context_t context)
178 /* Launch the thread */
179 pthread_mutex_lock(&(context->mutex));
180 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
181 "Unable to create a thread.");
182 pthread_cond_wait(&(context->cond), &(context->mutex));
183 pthread_mutex_unlock(&(context->mutex));
185 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
192 * \param code a main function
193 * \param startup_func a function to call when running the context for
194 * the first time and just before the main function \a code
195 * \param startup_arg the argument passed to the previous function (\a startup_func)
196 * \param cleanup_func a function to call when running the context, just after
197 the termination of the main function \a code
198 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
199 * \param argc first argument of function \a code
200 * \param argv seconde argument of function \a code
202 xbt_context_t xbt_context_new(xbt_context_function_t code,
203 void_f_pvoid_t startup_func, void *startup_arg,
204 void_f_pvoid_t cleanup_func, void *cleanup_arg,
205 int argc, char *argv[])
207 xbt_context_t res = NULL;
209 res = xbt_new0(s_xbt_context_t,1);
213 res->thread = xbt_new0(pthread_t,1);
214 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
215 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
217 /* FIXME: strerror is not thread safe */
218 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
219 res->uc.uc_link = NULL;
220 /* res->uc.uc_link = &(current_context->uc); */
221 /* WARNING : when this context is over, the current_context (i.e. the
222 father), is awaken... Theorically, the wrapper should prevent using
224 res->uc.uc_stack.ss_sp = res->stack;
225 res->uc.uc_stack.ss_size = STACK_SIZE;
229 res->startup_func = startup_func;
230 res->startup_arg = startup_arg;
231 res->cleanup_func = cleanup_func;
232 res->cleanup_arg = cleanup_arg;
234 xbt_swag_insert(res, context_living);
240 * Calling this function makes the current context yield. The context
241 * that scheduled it returns from xbt_context_schedule as if nothing
244 void xbt_context_yield(void)
246 __xbt_context_yield(current_context);
250 * \param context the winner
252 * Calling this function blocks the current context and schedule \a context.
253 * When \a context will call xbt_context_yield, it will return
254 * to this function as if nothing had happened.
256 void xbt_context_schedule(xbt_context_t context)
258 xbt_assert0((current_context==init_context),
259 "You are not supposed to run this function here!");
260 __xbt_context_yield(context);
264 * This function kill all existing context and free all the memory
265 * that has been allocated in this module.
267 void xbt_context_exit(void) {
268 xbt_context_t context=NULL;
270 xbt_context_empty_trash();
271 xbt_swag_free(context_to_destroy);
273 while((context=xbt_swag_extract(context_living)))
274 xbt_context_free(context);
276 xbt_swag_free(context_living);
278 init_context = current_context = NULL ;
282 * \param context poor victim
284 * This function simply kills \a context... scarry isn't it ?
286 void xbt_context_free(xbt_context_t context)
290 xbt_swag_remove(context, context_living);
291 for(i=0;i<context->argc; i++)
292 if(context->argv[i]) free(context->argv[i]);
293 if(context->argv) free(context->argv);
295 if(context->cleanup_func)
296 context->cleanup_func(context->cleanup_arg);
297 xbt_context_destroy(context);