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 */
48 #ifdef CONTEXT_UCONTEXT
49 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
51 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
54 else if (!strcmp(smx_context_factory_name, "ucontext")) {
56 #ifdef CONTEXT_UCONTEXT
57 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
59 xbt_die("The context factory 'ucontext' unavailable on your system");
62 else if (!strcmp(smx_context_factory_name, "thread")) {
63 /* use os threads (either pthreads or windows ones) */
64 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
66 else if (!strcmp(smx_context_factory_name, "raw")) {
67 /* use raw contexts */
68 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
71 xbt_die("Invalid context factory specified");
76 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
77 /* the __thread storage class is not available on this platform:
78 * use getspecific/setspecific instead to store the current context in each thread */
79 xbt_os_thread_key_create(&smx_current_context_key);
84 * This function is call by SIMIX_clean() to finalize the context module.
86 void SIMIX_context_mod_exit(void)
88 if (simix_global->context_factory) {
89 smx_pfn_context_factory_finalize_t finalize_factory;
91 /* finalize the context factory */
92 finalize_factory = simix_global->context_factory->finalize;
93 (*finalize_factory) (&simix_global->context_factory);
95 xbt_dict_remove((xbt_dict_t) _surf_cfg_set,"contexts/factory");
99 * \brief Sets the number of parallel threads to use
100 * for the user contexts.
102 * This function should be called before initializing SIMIX.
103 * A value of 1 means no parallelism.
104 * If the value is greater than 1, the thread support must be enabled.
106 * \param nb_threads the number of threads to use
108 XBT_INLINE void SIMIX_context_set_nthreads(int nb_threads) {
110 xbt_assert(nb_threads > 0, "Invalid number of parallel threads: %d", nb_threads);
112 if (nb_threads > 1) {
113 #ifndef CONTEXT_THREADS
114 THROWF(arg_error, 0, "No thread support for parallel context execution");
118 smx_parallel_contexts = nb_threads;
122 * \brief Returns the number of parallel threads used
123 * for the user contexts.
124 * \return the number of threads (1 means no parallelism)
126 XBT_INLINE int SIMIX_context_get_nthreads(void) {
127 return smx_parallel_contexts;
131 * \brief Returns whether some parallel threads are used
132 * for the user contexts.
133 * \return 1 if parallelism is used
135 XBT_INLINE int SIMIX_context_is_parallel(void) {
136 return smx_parallel_contexts > 1;
140 * \brief Sets the threshold above which user processes are run in parallel.
142 * If the number of threads is set to 1, there is no parallelism and this
143 * threshold has no effect.
145 * \param threshold when the number of user processes ready to run is above
146 * this threshold, they are run in parallel
148 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
149 smx_parallel_threshold = threshold;
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 Returns the current context of this thread.
167 * \return the current context of this thread
169 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
171 #ifdef HAVE_THREAD_LOCAL_STORAGE
172 return smx_current_context;
174 return xbt_os_thread_get_specific(smx_current_context_key);
179 * \brief Sets the current context of this thread.
180 * \param context the context to set
182 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
184 #ifdef HAVE_THREAD_LOCAL_STORAGE
185 smx_current_context = context;
187 xbt_os_thread_set_specific(smx_current_context_key, context);