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(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));
102 if(context->exception) free(context->exception);
107 static void *__context_wrapper(void *c)
109 xbt_context_t context = c;
113 DEBUG0("**** Lock ****");
114 pthread_mutex_lock(&(context->mutex));
115 DEBUG0("**** Releasing the prisonner ****");
116 pthread_cond_signal(&(context->cond));
117 DEBUG0("**** Going to Jail ****");
118 pthread_cond_wait(&(context->cond), &(context->mutex));
119 DEBUG0("**** Unlocking ****");
120 pthread_mutex_unlock(&(context->mutex));
123 if(context->startup_func)
124 context->startup_func(context->startup_arg);
126 DEBUG0("Calling the main function");
127 (context->code) (context->argc,context->argv);
129 for(i=0;i<context->argc; i++)
130 if(context->argv[i]) free(context->argv[i]);
131 if(context->argv) free(context->argv);
133 if(context->cleanup_func)
134 context->cleanup_func(context->cleanup_arg);
136 xbt_swag_remove(context, context_living);
137 xbt_swag_insert(context, context_to_destroy);
139 __xbt_context_yield(context);
140 xbt_assert0(0,"You're cannot be here!");
144 /* callback: context fetching */
145 static ex_ctx_t *__context_ex_ctx(void)
147 return current_context->exception;
150 /* callback: termination */
151 static void __context_ex_terminate(xbt_ex_t *e)
157 * \ingroup XBT_context
160 /** Context module initialization
162 * \warning It has to be called before using any other function of this module.
164 void xbt_context_init(void)
166 if(!current_context) {
167 current_context = init_context = xbt_new0(s_xbt_context_t,1);
168 init_context->exception = xbt_new(ex_ctx_t,1);
169 XBT_CTX_INITIALIZE(init_context->exception);
170 __xbt_ex_ctx = __context_ex_ctx;
171 __xbt_ex_terminate = __context_ex_terminate;
172 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
173 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
174 xbt_swag_insert(init_context, context_living);
178 /** Garbage collection
180 * Should be called some time to time to free the memory allocated for contexts
181 * that have finished executing their main functions.
183 void xbt_context_empty_trash(void)
185 xbt_context_t context=NULL;
187 while((context=xbt_swag_extract(context_to_destroy)))
188 xbt_context_destroy(context);
192 * \param context the context to start
194 * Calling this function prepares \a context to be run. It will
195 however run effectively only when calling #xbt_context_schedule
197 void xbt_context_start(xbt_context_t context)
200 /* Launch the thread */
201 DEBUG0("**** Locking ****");
202 pthread_mutex_lock(&(context->mutex));
203 DEBUG0("**** Pthread create ****");
204 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
205 "Unable to create a thread.");
206 DEBUG0("**** Going to jail ****");
207 pthread_cond_wait(&(context->cond), &(context->mutex));
208 DEBUG0("**** Unlocking ****");
209 pthread_mutex_unlock(&(context->mutex));
211 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
218 * \param code a main function
219 * \param startup_func a function to call when running the context for
220 * the first time and just before the main function \a code
221 * \param startup_arg the argument passed to the previous function (\a startup_func)
222 * \param cleanup_func a function to call when running the context, just after
223 the termination of the main function \a code
224 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
225 * \param argc first argument of function \a code
226 * \param argv seconde argument of function \a code
228 xbt_context_t xbt_context_new(xbt_context_function_t code,
229 void_f_pvoid_t startup_func, void *startup_arg,
230 void_f_pvoid_t cleanup_func, void *cleanup_arg,
231 int argc, char *argv[])
233 xbt_context_t res = NULL;
235 res = xbt_new0(s_xbt_context_t,1);
239 res->thread = xbt_new0(pthread_t,1);
240 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
241 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
243 /* FIXME: strerror is not thread safe */
244 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
245 res->uc.uc_link = NULL;
246 /* res->uc.uc_link = &(current_context->uc); */
247 /* WARNING : when this context is over, the current_context (i.e. the
248 father), is awaken... Theorically, the wrapper should prevent using
250 # ifndef USE_WIN_CONTEXT
251 res->uc.uc_stack.ss_sp = pth_skaddr_makecontext(res->stack,STACK_SIZE);
252 res->uc.uc_stack.ss_size = pth_sksize_makecontext(res->stack,STACK_SIZE);
253 # endif /* USE_WIN_CONTEXT */
254 #endif /* USE_PTHREADS or not */
257 res->startup_func = startup_func;
258 res->startup_arg = startup_arg;
259 res->cleanup_func = cleanup_func;
260 res->cleanup_arg = cleanup_arg;
261 res->exception = xbt_new(ex_ctx_t,1);
262 XBT_CTX_INITIALIZE(res->exception);
264 xbt_swag_insert(res, context_living);
270 * Calling this function makes the current context yield. The context
271 * that scheduled it returns from xbt_context_schedule as if nothing
274 void xbt_context_yield(void)
276 __xbt_context_yield(current_context);
280 * \param context the winner
282 * Calling this function blocks the current context and schedule \a context.
283 * When \a context will call xbt_context_yield, it will return
284 * to this function as if nothing had happened.
286 void xbt_context_schedule(xbt_context_t context)
288 xbt_assert0((current_context==init_context),
289 "You are not supposed to run this function here!");
290 __xbt_context_yield(context);
294 * This function kill all existing context and free all the memory
295 * that has been allocated in this module.
297 void xbt_context_exit(void) {
298 xbt_context_t context=NULL;
300 xbt_context_empty_trash();
301 xbt_swag_free(context_to_destroy);
303 while((context=xbt_swag_extract(context_living)))
304 xbt_context_free(context);
306 xbt_swag_free(context_living);
308 init_context = current_context = NULL ;
312 * \param context poor victim
314 * This function simply kills \a context... scarry isn't it ?
316 void xbt_context_free(xbt_context_t context)
320 xbt_swag_remove(context, context_living);
321 for(i=0;i<context->argc; i++)
322 if(context->argv[i]) free(context->argv[i]);
323 if(context->argv) free(context->argv);
325 if(context->cleanup_func)
326 context->cleanup_func(context->cleanup_arg);
327 xbt_context_destroy(context);