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"
17 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(xbt_ctx, xbt, "Context");
19 #define VOIRP(expr) DEBUG1(" {" #expr " = %p }", expr)
21 static xbt_context_t current_context = NULL;
22 static xbt_context_t init_context = NULL;
23 static xbt_swag_t context_to_destroy = NULL;
24 static xbt_swag_t context_living = NULL;
26 #ifndef USE_PTHREADS /* USE_PTHREADS and USE_CONTEXT are exclusive */
28 /* don't want to play with conditional compilation in automake tonight, sorry.
29 include directly the c file from here when needed. */
30 # include "context_win32.c"
31 # define USE_WIN_CONTEXT
35 static void __xbt_context_yield(xbt_context_t context)
37 xbt_assert0(current_context,"You have to call context_init() first.");
39 DEBUG2("--------- current_context (%p) is yielding to context(%p) ---------",
40 current_context,context);
44 xbt_context_t self = current_context;
45 DEBUG0("**** Locking ****");
46 pthread_mutex_lock(&(context->mutex));
47 DEBUG0("**** Updating current_context ****");
48 current_context = context;
49 DEBUG0("**** Releasing the prisonner ****");
50 pthread_cond_signal(&(context->cond));
51 DEBUG0("**** Going to jail ****");
52 pthread_cond_wait(&(context->cond), &(context->mutex));
53 DEBUG0("**** Unlocking ****");
54 pthread_mutex_unlock(&(context->mutex));
55 DEBUG0("**** Updating current_context ****");
56 current_context = self;
60 VOIRP(current_context->save);
63 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_exit(xbt_context_t context ,int value)
110 DEBUG0("Freeing arguments");
111 for(i=0;i<context->argc; i++)
112 if(context->argv[i]) free(context->argv[i]);
113 if(context->argv) free(context->argv);
115 if(context->cleanup_func) {
116 DEBUG0("Calling cleanup function");
117 context->cleanup_func(context->cleanup_arg);
120 DEBUG0("Putting context in the to_destroy set");
121 xbt_swag_remove(context, context_living);
122 xbt_swag_insert(context, context_to_destroy);
123 DEBUG0("Context put in the to_destroy set");
127 DEBUG0("**** Locking ****");
128 pthread_mutex_lock(&(context->mutex));
129 DEBUG0("**** Updating current_context ****");
130 current_context = context;
131 DEBUG0("**** Releasing the prisonner ****");
132 pthread_cond_signal(&(context->cond));
133 DEBUG0("**** Unlocking ****");
134 pthread_mutex_unlock(&(context->mutex));
135 DEBUG0("**** Exiting ****");
138 __xbt_context_yield(context);
140 xbt_assert0(0,"You can't be here!");
143 static void *__context_wrapper(void *c)
145 xbt_context_t context = c;
148 DEBUG2("**[%p:%p]** Lock ****",context,(void*)pthread_self());
149 pthread_mutex_lock(&(context->mutex));
150 DEBUG2("**[%p:%p]** Releasing the prisonner ****",context,(void*)pthread_self());
151 pthread_cond_signal(&(context->cond));
152 DEBUG2("**[%p:%p]** Going to Jail ****",context,(void*)pthread_self());
153 pthread_cond_wait(&(context->cond), &(context->mutex));
154 DEBUG2("**[%p:%p]** Unlocking ****",context,(void*)pthread_self());
155 pthread_mutex_unlock(&(context->mutex));
158 if(context->startup_func)
159 context->startup_func(context->startup_arg);
161 DEBUG0("Calling the main function");
163 __context_exit(context, (context->code) (context->argc,context->argv));
167 /* callback: context fetching */
168 static ex_ctx_t *__context_ex_ctx(void)
170 return current_context->exception;
173 /* callback: termination */
174 static void __context_ex_terminate(xbt_ex_t *e) {
178 /* FIXME: there should be a configuration variable to choose this
179 if(current_context!=init_context)
180 __context_exit(current_context, e->value);
187 * \ingroup XBT_context
190 /** Context module initialization
192 * \warning It has to be called before using any other function of this module.
194 void xbt_context_init(void)
196 if(!current_context) {
197 current_context = init_context = xbt_new0(s_xbt_context_t,1);
198 init_context->exception = xbt_new(ex_ctx_t,1);
199 XBT_CTX_INITIALIZE(init_context->exception);
200 __xbt_ex_ctx = __context_ex_ctx;
201 __xbt_ex_terminate = __context_ex_terminate;
202 context_to_destroy = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
203 context_living = xbt_swag_new(xbt_swag_offset(*current_context,hookup));
204 xbt_swag_insert(init_context, context_living);
208 /** Garbage collection
210 * Should be called some time to time to free the memory allocated for contexts
211 * that have finished executing their main functions.
213 void xbt_context_empty_trash(void)
215 xbt_context_t context=NULL;
217 while((context=xbt_swag_extract(context_to_destroy)))
218 xbt_context_destroy(context);
222 * \param context the context to start
224 * Calling this function prepares \a context to be run. It will
225 however run effectively only when calling #xbt_context_schedule
227 void xbt_context_start(xbt_context_t context)
230 /* Launch the thread */
231 DEBUG1("**[%p]** Locking ****",context);
232 pthread_mutex_lock(&(context->mutex));
233 DEBUG1("**[%p]** Pthread create ****",context);
234 xbt_assert0(!pthread_create(context->thread, NULL, __context_wrapper, context),
235 "Unable to create a thread.");
236 DEBUG2("**[%p]** Pthread created : %p ****",context,(void*)(*(context->thread)));
237 DEBUG1("**[%p]** Going to jail ****",context);
238 pthread_cond_wait(&(context->cond), &(context->mutex));
239 DEBUG1("**[%p]** Unlocking ****",context);
240 pthread_mutex_unlock(&(context->mutex));
242 makecontext (&(context->uc), (void (*) (void)) __context_wrapper,
249 * \param code a main function
250 * \param startup_func a function to call when running the context for
251 * the first time and just before the main function \a code
252 * \param startup_arg the argument passed to the previous function (\a startup_func)
253 * \param cleanup_func a function to call when running the context, just after
254 the termination of the main function \a code
255 * \param cleanup_arg the argument passed to the previous function (\a cleanup_func)
256 * \param argc first argument of function \a code
257 * \param argv seconde argument of function \a code
259 xbt_context_t xbt_context_new(xbt_context_function_t code,
260 void_f_pvoid_t startup_func, void *startup_arg,
261 void_f_pvoid_t cleanup_func, void *cleanup_arg,
262 int argc, char *argv[])
264 xbt_context_t res = NULL;
266 res = xbt_new0(s_xbt_context_t,1);
270 res->thread = xbt_new0(pthread_t,1);
271 xbt_assert0(!pthread_mutex_init(&(res->mutex), NULL), "Mutex initialization error");
272 xbt_assert0(!pthread_cond_init(&(res->cond), NULL), "Condition initialization error");
274 /* FIXME: strerror is not thread safe */
275 xbt_assert2(getcontext(&(res->uc))==0,"Error in context saving: %d (%s)", errno, strerror(errno));
276 res->uc.uc_link = NULL;
277 /* res->uc.uc_link = &(current_context->uc); */
278 /* WARNING : when this context is over, the current_context (i.e. the
279 father), is awaken... Theorically, the wrapper should prevent using
281 # ifndef USE_WIN_CONTEXT
282 res->uc.uc_stack.ss_sp = pth_skaddr_makecontext(res->stack,STACK_SIZE);
283 res->uc.uc_stack.ss_size = pth_sksize_makecontext(res->stack,STACK_SIZE);
284 # endif /* USE_WIN_CONTEXT */
285 #endif /* USE_PTHREADS or not */
288 res->startup_func = startup_func;
289 res->startup_arg = startup_arg;
290 res->cleanup_func = cleanup_func;
291 res->cleanup_arg = cleanup_arg;
292 res->exception = xbt_new(ex_ctx_t,1);
293 XBT_CTX_INITIALIZE(res->exception);
295 xbt_swag_insert(res, context_living);
301 * Calling this function makes the current context yield. The context
302 * that scheduled it returns from xbt_context_schedule as if nothing
305 void xbt_context_yield(void)
307 __xbt_context_yield(current_context);
311 * \param context the winner
313 * Calling this function blocks the current context and schedule \a context.
314 * When \a context will call xbt_context_yield, it will return
315 * to this function as if nothing had happened.
317 void xbt_context_schedule(xbt_context_t context)
319 DEBUG1("Scheduling %p",context);
320 xbt_assert0((current_context==init_context),
321 "You are not supposed to run this function here!");
322 __xbt_context_yield(context);
326 * This function kill all existing context and free all the memory
327 * that has been allocated in this module.
329 void xbt_context_exit(void) {
330 xbt_context_t context=NULL;
332 xbt_context_empty_trash();
333 xbt_swag_free(context_to_destroy);
335 while((context=xbt_swag_extract(context_living)))
336 xbt_context_free(context);
338 xbt_swag_free(context_living);
340 init_context = current_context = NULL ;
344 * \param context poor victim
346 * This function simply kills \a context... scarry isn't it ?
348 void xbt_context_free(xbt_context_t context)
352 xbt_swag_remove(context, context_living);
353 for(i=0;i<context->argc; i++)
354 if(context->argv[i]) free(context->argv[i]);
355 if(context->argv) free(context->argv);
357 if(context->cleanup_func)
358 context->cleanup_func(context->cleanup_arg);
359 xbt_context_destroy(context);