1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009, 2010. The SimGrid Team.
4 * All rights reserved. */
6 /* This program is free software; you can redistribute it and/or modify it
7 * under the terms of the license (GNU LGPL) which comes with this package. */
12 #include "xbt/xbt_os_thread.h"
13 #include "src/simix/private.h"
14 #include "simix/context.h"
15 #include "gras_config.h"
17 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
18 "Context switching mecanism");
20 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
21 smx_ctx_factory_initializer_t smx_factory_initializer_to_use = NULL;
22 int smx_context_stack_size = 128 * 1024;
24 #ifdef HAVE_THREAD_LOCAL_STORAGE
25 __thread smx_context_t smx_current_context;
27 smx_context_t smx_current_context; /* define it anyway, will be used in non-parallel mode */
28 static xbt_os_thread_key_t smx_current_context_key = 0;
31 static int smx_parallel_contexts = 1;
32 static int smx_parallel_threshold = 2;
35 * This function is called by SIMIX_global_init() to initialize the context module.
37 void SIMIX_context_mod_init(void)
39 if (!simix_global->context_factory) {
40 /* select the context factory to use to create the contexts */
41 if (smx_factory_initializer_to_use) {
42 (*smx_factory_initializer_to_use)(&(simix_global->context_factory));
44 else { /* use the factory specified by --cfg=contexts/factory:value */
46 if (smx_context_factory_name == NULL) {
47 /* use the default factory */
49 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
50 #elif CONTEXT_UCONTEXT
51 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
53 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
56 else if (!strcmp(smx_context_factory_name, "ucontext")) {
58 #ifdef CONTEXT_UCONTEXT
59 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
61 xbt_die("The context factory 'ucontext' unavailable on your system");
64 else if (!strcmp(smx_context_factory_name, "thread")) {
65 /* use os threads (either pthreads or windows ones) */
66 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
68 else if (!strcmp(smx_context_factory_name, "raw")) {
69 /* use raw contexts */
70 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
73 xbt_die("Invalid context factory specified");
78 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
79 /* the __thread storage class is not available on this platform:
80 * use getspecific/setspecific instead to store the current context in each thread */
81 xbt_os_thread_key_create(&smx_current_context_key);
86 * This function is call by SIMIX_clean() to finalize the context module.
88 void SIMIX_context_mod_exit(void)
90 if (simix_global->context_factory) {
91 smx_pfn_context_factory_finalize_t finalize_factory;
93 /* finalize the context factory */
94 finalize_factory = simix_global->context_factory->finalize;
95 (*finalize_factory) (&simix_global->context_factory);
97 xbt_dict_remove((xbt_dict_t) _surf_cfg_set,"contexts/factory");
101 * \brief Sets the number of parallel threads to use
102 * for the user contexts.
104 * This function should be called before initializing SIMIX.
105 * A value of 1 means no parallelism.
106 * If the value is greater than 1, the thread support must be enabled.
108 * \param nb_threads the number of threads to use
110 XBT_INLINE void SIMIX_context_set_nthreads(int nb_threads) {
112 xbt_assert(nb_threads > 0, "Invalid number of parallel threads: %d", nb_threads);
114 if (nb_threads > 1) {
115 #ifndef CONTEXT_THREADS
116 THROWF(arg_error, 0, "No thread support for parallel context execution");
120 smx_parallel_contexts = nb_threads;
124 * \brief Returns the number of parallel threads used
125 * for the user contexts.
126 * \return the number of threads (1 means no parallelism)
128 XBT_INLINE int SIMIX_context_get_nthreads(void) {
129 return smx_parallel_contexts;
133 * \brief Returns whether some parallel threads are used
134 * for the user contexts.
135 * \return 1 if parallelism is used
137 XBT_INLINE int SIMIX_context_is_parallel(void) {
138 return smx_parallel_contexts > 1;
142 * \brief Sets the threshold above which user processes are run in parallel.
144 * If the number of threads is set to 1, there is no parallelism and this
145 * threshold has no effect.
147 * \param threshold when the number of user processes ready to run is above
148 * this threshold, they are run in parallel
150 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
151 smx_parallel_threshold = threshold;
155 * \brief Returns the threshold above which user processes are run in parallel.
157 * If the number of threads is set to 1, there is no parallelism and this
158 * threshold has no effect.
160 * \return when the number of user processes ready to run is above
161 * this threshold, they are run in parallel
163 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
164 return smx_parallel_threshold;
168 * \brief Returns the current context of this thread.
169 * \return the current context of this thread
171 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
173 #ifdef HAVE_THREAD_LOCAL_STORAGE
174 return smx_current_context;
176 return xbt_os_thread_get_specific(smx_current_context_key);
181 * \brief Sets the current context of this thread.
182 * \param context the context to set
184 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
186 #ifdef HAVE_THREAD_LOCAL_STORAGE
187 smx_current_context = context;
189 xbt_os_thread_set_specific(smx_current_context_key, context);