1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009 - 2011. 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 static __thread smx_context_t smx_current_context_parallel;
27 static xbt_os_thread_key_t smx_current_context_key = 0;
29 static smx_context_t smx_current_context_serial;
30 static int smx_parallel_contexts = 1;
31 static int smx_parallel_threshold = 2;
34 * This function is called by SIMIX_global_init() to initialize the context module.
36 void SIMIX_context_mod_init(void)
38 if (!simix_global->context_factory) {
39 /* select the context factory to use to create the contexts */
40 if (smx_factory_initializer_to_use) {
41 smx_factory_initializer_to_use(&simix_global->context_factory);
43 else { /* use the factory specified by --cfg=contexts/factory:value */
45 if (smx_context_factory_name == NULL) {
46 /* use the default factory */
48 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
49 #elif CONTEXT_UCONTEXT
50 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
52 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
55 else if (!strcmp(smx_context_factory_name, "ucontext")) {
57 #ifdef CONTEXT_UCONTEXT
58 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
60 xbt_die("The context factory 'ucontext' unavailable on your system");
63 else if (!strcmp(smx_context_factory_name, "thread")) {
64 /* use os threads (either pthreads or windows ones) */
65 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
67 else if (!strcmp(smx_context_factory_name, "raw")) {
68 /* use raw contexts */
69 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
72 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
74 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
76 XBT_ERROR(" (raw contextes are disabled at compilation time on this machine -- check configure logs for details)");
78 #ifdef CONTEXT_UCONTEXT
79 XBT_ERROR(" ucontext: classical system V contextes (implemented with makecontext, swapcontext and friends)");
81 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
83 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
84 xbt_die("Please use a valid factory.");
89 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
90 /* the __thread storage class is not available on this platform:
91 * use getspecific/setspecific instead to store the current context in each thread */
92 xbt_os_thread_key_create(&smx_current_context_key);
97 * This function is call by SIMIX_clean() to finalize the context module.
99 void SIMIX_context_mod_exit(void)
101 if (simix_global->context_factory) {
102 smx_pfn_context_factory_finalize_t finalize_factory;
104 /* finalize the context factory */
105 finalize_factory = simix_global->context_factory->finalize;
106 finalize_factory(&simix_global->context_factory);
108 xbt_dict_remove((xbt_dict_t) _surf_cfg_set,"contexts/factory");
112 * \brief Returns whether some parallel threads are used
113 * for the user contexts.
114 * \return 1 if parallelism is used
116 XBT_INLINE int SIMIX_context_is_parallel(void) {
117 return smx_parallel_contexts > 1;
121 * \brief Returns the number of parallel threads used
122 * for the user contexts.
123 * \return the number of threads (1 means no parallelism)
125 XBT_INLINE int SIMIX_context_get_nthreads(void) {
126 return smx_parallel_contexts;
130 * \brief Sets the number of parallel threads to use
131 * for the user contexts.
133 * This function should be called before initializing SIMIX.
134 * A value of 1 means no parallelism.
135 * If the value is greater than 1, the thread support must be enabled.
137 * \param nb_threads the number of threads to use
139 XBT_INLINE void SIMIX_context_set_nthreads(int nb_threads) {
141 xbt_assert(nb_threads > 0, "Invalid number of parallel threads: %d", nb_threads);
143 if (nb_threads > 1) {
144 #ifndef CONTEXT_THREADS
145 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
149 smx_parallel_contexts = nb_threads;
153 * \brief Returns the threshold above which user processes are run in parallel.
155 * If the number of threads is set to 1, there is no parallelism and this
156 * threshold has no effect.
158 * \return when the number of user processes ready to run is above
159 * this threshold, they are run in parallel
161 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
162 return smx_parallel_threshold;
166 * \brief Sets the threshold above which user processes are run in parallel.
168 * If the number of threads is set to 1, there is no parallelism and this
169 * threshold has no effect.
171 * \param threshold when the number of user processes ready to run is above
172 * this threshold, they are run in parallel
174 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
175 smx_parallel_threshold = threshold;
179 * \brief Returns the synchronization mode used when processes are run in
181 * \return how threads are synchronized if processes are run in parallel
183 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
184 e_xbt_parmap_mode_t mode = XBT_PARMAP_FUTEX;
185 const char* mode_name = xbt_cfg_get_string(_surf_cfg_set, "contexts/synchro");
186 if (!strcmp(mode_name, "posix")) {
187 mode = XBT_PARMAP_POSIX;
189 else if (!strcmp(mode_name, "futex")) {
190 mode = XBT_PARMAP_FUTEX;
192 else if (!strcmp(mode_name, "busy_wait")) {
193 mode = XBT_PARMAP_BUSY_WAIT;
196 XBT_WARN("Command line setting of the parallel synchronization mode should "
197 "be one of \"posix\", \"futex\" or \"busy_wait\"");
203 * \brief Sets the synchronization mode to use when processes are run in
205 * \param mode how to synchronize threads if processes are run in parallel
207 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
208 if (mode == XBT_PARMAP_POSIX) {
209 xbt_cfg_set_string(_surf_cfg_set, "contexts/synchro", "posix");
211 else if (mode == XBT_PARMAP_FUTEX) {
212 xbt_cfg_set_string(_surf_cfg_set, "contexts/synchro", "futex");
214 else if (XBT_PARMAP_BUSY_WAIT) {
215 xbt_cfg_set_string(_surf_cfg_set, "contexts/synchro", "busy_wait");
218 XBT_WARN("Command line setting of the parallel synchronization mode should "
219 "be one of \"posix\", \"futex\" or \"busy_wait\"");
224 * \brief Returns the current context of this thread.
225 * \return the current context of this thread
227 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
229 if (SIMIX_context_is_parallel()) {
230 #ifdef HAVE_THREAD_LOCAL_STORAGE
231 return smx_current_context_parallel;
233 return xbt_os_thread_get_specific(smx_current_context_key);
237 return smx_current_context_serial;
242 * \brief Sets the current context of this thread.
243 * \param context the context to set
245 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
247 if (SIMIX_context_is_parallel()) {
248 #ifdef HAVE_THREAD_LOCAL_STORAGE
249 smx_current_context_parallel = context;
251 xbt_os_thread_set_specific(smx_current_context_key, context);
255 smx_current_context_serial = context;