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"
16 #include "simgrid/modelchecker.h"
19 #ifdef HAVE_VALGRIND_VALGRIND_H
20 # include <valgrind/valgrind.h>
23 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
24 "Context switching mechanism");
26 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
27 smx_ctx_factory_initializer_t smx_factory_initializer_to_use = NULL;
28 int smx_context_stack_size;
29 int smx_context_stack_size_was_set = 0;
30 int smx_context_guard_size;
31 int smx_context_guard_size_was_set = 0;
32 #ifdef HAVE_THREAD_LOCAL_STORAGE
33 static __thread smx_context_t smx_current_context_parallel;
35 static xbt_os_thread_key_t smx_current_context_key = 0;
37 static smx_context_t smx_current_context_serial;
38 static int smx_parallel_contexts = 1;
39 static int smx_parallel_threshold = 2;
40 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
43 * This function is called by SIMIX_global_init() to initialize the context module.
45 void SIMIX_context_mod_init(void)
47 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
48 /* the __thread storage class is not available on this platform:
49 * use getspecific/setspecific instead to store the current context in each thread */
50 xbt_os_thread_key_create(&smx_current_context_key);
52 if (!simix_global->context_factory) {
53 /* select the context factory to use to create the contexts */
54 if (smx_factory_initializer_to_use) {
55 smx_factory_initializer_to_use(&simix_global->context_factory);
57 else { /* use the factory specified by --cfg=contexts/factory:value */
60 if (!strcmp(smx_context_factory_name, "thread")) {
61 /* use os threads (either pthreads or windows ones) */
62 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
64 #ifdef CONTEXT_UCONTEXT
65 else if (!strcmp(smx_context_factory_name, "ucontext")) {
67 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
71 else if (!strcmp(smx_context_factory_name, "raw")) {
72 /* use raw contexts */
73 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
77 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
79 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
81 XBT_ERROR(" (raw contexts are disabled at compilation time on this machine -- check configure logs for details)");
83 #ifdef CONTEXT_UCONTEXT
84 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
86 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
88 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
89 xbt_die("Please use a valid factory.");
96 * This function is called by SIMIX_clean() to finalize the context module.
98 void SIMIX_context_mod_exit(void)
100 if (simix_global->context_factory) {
101 smx_pfn_context_factory_finalize_t finalize_factory;
103 /* finalize the context factory */
104 finalize_factory = simix_global->context_factory->finalize;
105 finalize_factory(&simix_global->context_factory);
107 xbt_dict_remove((xbt_dict_t) _sg_cfg_set,"contexts/factory");
110 void *SIMIX_context_stack_new(void)
114 if (smx_context_guard_size > 0 && !MC_is_active()) {
115 size_t size = smx_context_stack_size + smx_context_guard_size;
117 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
118 * pointer returned by xbt_malloc0. */
119 char *alloc = xbt_malloc0(size + xbt_pagesize);
120 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
121 *((void **)stack - 1) = alloc;
123 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
124 xbt_die("Failed to allocate stack.");
126 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
127 XBT_WARN("Failed to protect stack: %s", strerror(errno));
128 /* That's not fatal, pursue anyway. */
130 stack = (char *)stack + smx_context_guard_size;
132 stack = xbt_malloc0(smx_context_stack_size);
135 #ifdef HAVE_VALGRIND_VALGRIND_H
136 unsigned int valgrind_stack_id =
137 VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
138 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id,
139 sizeof valgrind_stack_id);
145 void SIMIX_context_stack_delete(void *stack)
150 #ifdef HAVE_VALGRIND_VALGRIND_H
151 unsigned int valgrind_stack_id;
152 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size,
153 sizeof valgrind_stack_id);
154 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
157 if (smx_context_guard_size > 0 && !MC_is_active()) {
158 stack = (char *)stack - smx_context_guard_size;
159 if (mprotect(stack, smx_context_guard_size,
160 PROT_READ | PROT_WRITE | PROT_EXEC) == -1) {
161 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
162 /* try to pursue anyway */
165 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
166 stack = *((void **)stack - 1);
173 * \brief Returns whether some parallel threads are used
174 * for the user contexts.
175 * \return 1 if parallelism is used
177 XBT_INLINE int SIMIX_context_is_parallel(void) {
178 return smx_parallel_contexts > 1;
182 * \brief Returns the number of parallel threads used
183 * for the user contexts.
184 * \return the number of threads (1 means no parallelism)
186 XBT_INLINE int SIMIX_context_get_nthreads(void) {
187 return smx_parallel_contexts;
191 * \brief Sets the number of parallel threads to use
192 * for the user contexts.
194 * This function should be called before initializing SIMIX.
195 * A value of 1 means no parallelism (1 thread only).
196 * If the value is greater than 1, the thread support must be enabled.
198 * \param nb_threads the number of threads to use
200 void SIMIX_context_set_nthreads(int nb_threads) {
202 nb_threads = xbt_os_get_numcores();
203 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
206 if (nb_threads > 1) {
207 #ifndef CONTEXT_THREADS
208 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
211 smx_parallel_contexts = nb_threads;
215 * \brief Returns the threshold above which user processes are run in parallel.
217 * If the number of threads is set to 1, there is no parallelism and this
218 * threshold has no effect.
220 * \return when the number of user processes ready to run is above
221 * this threshold, they are run in parallel
223 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
224 return smx_parallel_threshold;
228 * \brief Sets the threshold above which user processes are run in parallel.
230 * If the number of threads is set to 1, there is no parallelism and this
231 * threshold has no effect.
233 * \param threshold when the number of user processes ready to run is above
234 * this threshold, they are run in parallel
236 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
237 smx_parallel_threshold = threshold;
241 * \brief Returns the synchronization mode used when processes are run in
243 * \return how threads are synchronized if processes are run in parallel
245 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
246 return smx_parallel_synchronization_mode;
250 * \brief Sets the synchronization mode to use when processes are run in
252 * \param mode how to synchronize threads if processes are run in parallel
254 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
255 smx_parallel_synchronization_mode = mode;
259 * \brief Returns the current context of this thread.
260 * \return the current context of this thread
262 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
264 if (SIMIX_context_is_parallel()) {
265 #ifdef HAVE_THREAD_LOCAL_STORAGE
266 return smx_current_context_parallel;
268 return xbt_os_thread_get_specific(smx_current_context_key);
272 return smx_current_context_serial;
277 * \brief Sets the current context of this thread.
278 * \param context the context to set
280 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
282 if (SIMIX_context_is_parallel()) {
283 #ifdef HAVE_THREAD_LOCAL_STORAGE
284 smx_current_context_parallel = context;
286 xbt_os_thread_set_specific(smx_current_context_key, context);
290 smx_current_context_serial = context;