1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2014. 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 "smx_private.h"
14 #include "simgrid/sg_config.h"
15 #include "internal_config.h"
17 #ifdef HAVE_VALGRIND_VALGRIND_H
18 # include <valgrind/valgrind.h>
21 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
22 "Context switching mechanism");
24 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
25 smx_ctx_factory_initializer_t smx_factory_initializer_to_use = NULL;
26 int smx_context_stack_size;
27 int smx_context_stack_size_was_set = 0;
28 int smx_context_guard_size;
29 int smx_context_guard_size_was_set = 0;
30 #ifdef HAVE_THREAD_LOCAL_STORAGE
31 static __thread smx_context_t smx_current_context_parallel;
33 static xbt_os_thread_key_t smx_current_context_key = 0;
35 static smx_context_t smx_current_context_serial;
36 static int smx_parallel_contexts = 1;
37 static int smx_parallel_threshold = 2;
38 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
41 * This function is called by SIMIX_global_init() to initialize the context module.
43 void SIMIX_context_mod_init(void)
45 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
46 /* the __thread storage class is not available on this platform:
47 * use getspecific/setspecific instead to store the current context in each thread */
48 xbt_os_thread_key_create(&smx_current_context_key);
50 if (!simix_global->context_factory) {
51 /* select the context factory to use to create the contexts */
52 if (smx_factory_initializer_to_use) {
53 smx_factory_initializer_to_use(&simix_global->context_factory);
55 else { /* use the factory specified by --cfg=contexts/factory:value */
58 if (!strcmp(smx_context_factory_name, "thread")) {
59 /* use os threads (either pthreads or windows ones) */
60 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
62 #ifdef CONTEXT_UCONTEXT
63 else if (!strcmp(smx_context_factory_name, "ucontext")) {
65 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
69 else if (!strcmp(smx_context_factory_name, "raw")) {
70 /* use raw contexts */
71 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
75 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
77 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
79 XBT_ERROR(" (raw contexts are disabled at compilation time on this machine -- check configure logs for details)");
81 #ifdef CONTEXT_UCONTEXT
82 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
84 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
86 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
87 xbt_die("Please use a valid factory.");
94 * This function is called by SIMIX_clean() to finalize the context module.
96 void SIMIX_context_mod_exit(void)
98 if (simix_global->context_factory) {
99 smx_pfn_context_factory_finalize_t finalize_factory;
101 /* finalize the context factory */
102 finalize_factory = simix_global->context_factory->finalize;
103 finalize_factory(&simix_global->context_factory);
105 xbt_dict_remove((xbt_dict_t) _sg_cfg_set,"contexts/factory");
108 void *SIMIX_context_stack_new(void)
110 void *stack = xbt_malloc0(smx_context_stack_size);
112 #ifdef HAVE_VALGRIND_VALGRIND_H
113 unsigned int valgrind_stack_id =
114 VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
115 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id,
116 sizeof valgrind_stack_id);
122 void SIMIX_context_stack_delete(void *stack)
127 #ifdef HAVE_VALGRIND_VALGRIND_H
128 unsigned int valgrind_stack_id;
129 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size,
130 sizeof valgrind_stack_id);
131 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
138 * \brief Returns whether some parallel threads are used
139 * for the user contexts.
140 * \return 1 if parallelism is used
142 XBT_INLINE int SIMIX_context_is_parallel(void) {
143 return smx_parallel_contexts > 1;
147 * \brief Returns the number of parallel threads used
148 * for the user contexts.
149 * \return the number of threads (1 means no parallelism)
151 XBT_INLINE int SIMIX_context_get_nthreads(void) {
152 return smx_parallel_contexts;
156 * \brief Sets the number of parallel threads to use
157 * for the user contexts.
159 * This function should be called before initializing SIMIX.
160 * A value of 1 means no parallelism (1 thread only).
161 * If the value is greater than 1, the thread support must be enabled.
163 * \param nb_threads the number of threads to use
165 void SIMIX_context_set_nthreads(int nb_threads) {
167 nb_threads = xbt_os_get_numcores();
168 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
171 if (nb_threads > 1) {
172 #ifndef CONTEXT_THREADS
173 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
176 smx_parallel_contexts = nb_threads;
180 * \brief Returns the threshold above which user processes are run in parallel.
182 * If the number of threads is set to 1, there is no parallelism and this
183 * threshold has no effect.
185 * \return when the number of user processes ready to run is above
186 * this threshold, they are run in parallel
188 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
189 return smx_parallel_threshold;
193 * \brief Sets the threshold above which user processes are run in parallel.
195 * If the number of threads is set to 1, there is no parallelism and this
196 * threshold has no effect.
198 * \param threshold when the number of user processes ready to run is above
199 * this threshold, they are run in parallel
201 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
202 smx_parallel_threshold = threshold;
206 * \brief Returns the synchronization mode used when processes are run in
208 * \return how threads are synchronized if processes are run in parallel
210 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
211 return smx_parallel_synchronization_mode;
215 * \brief Sets the synchronization mode to use when processes are run in
217 * \param mode how to synchronize threads if processes are run in parallel
219 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
220 smx_parallel_synchronization_mode = mode;
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;