1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2015. 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. */
9 #include "src/portable.h"
12 #include "xbt/xbt_os_thread.h"
13 #include "smx_private.h"
14 #include "simgrid/sg_config.h"
15 #include "src/internal_config.h"
16 #include "simgrid/modelchecker.h"
27 #define _aligned_malloc __mingw_aligned_malloc
28 #define _aligned_free __mingw_aligned_free
31 #ifdef HAVE_VALGRIND_VALGRIND_H
32 # include <valgrind/valgrind.h>
35 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
36 "Context switching mechanism");
38 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
39 smx_ctx_factory_initializer_t smx_factory_initializer_to_use = NULL;
40 int smx_context_stack_size;
41 int smx_context_stack_size_was_set = 0;
42 int smx_context_guard_size;
43 int smx_context_guard_size_was_set = 0;
44 #ifdef HAVE_THREAD_LOCAL_STORAGE
45 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
47 static xbt_os_thread_key_t smx_current_context_key = 0;
49 static smx_context_t smx_current_context_serial;
50 static int smx_parallel_contexts = 1;
51 static int smx_parallel_threshold = 2;
52 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
55 * This function is called by SIMIX_global_init() to initialize the context module.
57 void SIMIX_context_mod_init(void)
59 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
60 /* the __thread storage class is not available on this platform:
61 * use getspecific/setspecific instead to store the current context in each thread */
62 xbt_os_thread_key_create(&smx_current_context_key);
64 if (!simix_global->context_factory) {
65 /* select the context factory to use to create the contexts */
66 if (smx_factory_initializer_to_use) {
67 smx_factory_initializer_to_use(&simix_global->context_factory);
69 else { /* use the factory specified by --cfg=contexts/factory:value */
72 if (!strcmp(smx_context_factory_name, "thread")) {
73 /* use os threads (either pthreads or windows ones) */
74 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
76 #ifdef CONTEXT_UCONTEXT
77 else if (!strcmp(smx_context_factory_name, "ucontext")) {
79 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
83 else if (!strcmp(smx_context_factory_name, "raw")) {
84 /* use raw contexts */
85 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
88 #ifdef HAVE_BOOST_CONTEXT
89 else if (!strcmp(smx_context_factory_name, "boost")) {
90 /* use Boost.Context */
91 SIMIX_ctx_boost_factory_init(&simix_global->context_factory);
95 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
97 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
99 XBT_ERROR(" (raw contexts are disabled at compilation time on this machine -- check configure logs for details)");
101 #ifdef CONTEXT_UCONTEXT
102 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
104 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
106 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
107 xbt_die("Please use a valid factory.");
114 * This function is called by SIMIX_clean() to finalize the context module.
116 void SIMIX_context_mod_exit(void)
118 if (simix_global->context_factory) {
119 smx_pfn_context_factory_finalize_t finalize_factory;
121 /* finalize the context factory */
122 finalize_factory = simix_global->context_factory->finalize;
123 finalize_factory(&simix_global->context_factory);
125 xbt_dict_remove((xbt_dict_t) _sg_cfg_set,"contexts/factory");
128 void *SIMIX_context_stack_new(void)
132 /* FIXME: current code for stack overflow protection assumes that stacks are
133 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
134 * after the stack when PTH_STACKGROWTH == 1. */
136 if (smx_context_guard_size > 0 && !MC_is_active()) {
138 #if defined(_XBT_WIN32) || (PTH_STACKGROWTH != -1)
139 static int warned_once = 0;
141 XBT_WARN("Stack overflow protection is known to be broken on your system. Either you're on Windows or PTH_STACKGROWTH != -1 (current value is %d).",
147 size_t size = smx_context_stack_size + smx_context_guard_size;
149 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
150 * pointer returned by xbt_malloc0. */
151 char *alloc = xbt_malloc0(size + xbt_pagesize);
152 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
153 *((void **)stack - 1) = alloc;
154 #elif !defined(_XBT_WIN32)
155 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
156 xbt_die("Failed to allocate stack.");
158 stack = _aligned_malloc(size, xbt_pagesize);
162 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
163 xbt_die("Failed to protect stack: %s", strerror(errno));
164 /* This is fatal. We are going to fail at some point when
165 we tryi reusing this. */
168 stack = (char *)stack + smx_context_guard_size;
170 stack = xbt_malloc0(smx_context_stack_size);
173 #ifdef HAVE_VALGRIND_VALGRIND_H
174 unsigned int valgrind_stack_id =
175 VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
176 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id,
177 sizeof valgrind_stack_id);
183 void SIMIX_context_stack_delete(void *stack)
188 #ifdef HAVE_VALGRIND_VALGRIND_H
189 unsigned int valgrind_stack_id;
190 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size,
191 sizeof valgrind_stack_id);
192 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
196 if (smx_context_guard_size > 0 && !MC_is_active()) {
197 stack = (char *)stack - smx_context_guard_size;
198 if (mprotect(stack, smx_context_guard_size,
199 PROT_READ | PROT_WRITE) == -1) {
200 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
201 /* try to pursue anyway */
204 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
205 stack = *((void **)stack - 1);
214 * \brief Returns whether some parallel threads are used
215 * for the user contexts.
216 * \return 1 if parallelism is used
218 XBT_INLINE int SIMIX_context_is_parallel(void) {
219 return smx_parallel_contexts > 1;
223 * \brief Returns the number of parallel threads used
224 * for the user contexts.
225 * \return the number of threads (1 means no parallelism)
227 XBT_INLINE int SIMIX_context_get_nthreads(void) {
228 return smx_parallel_contexts;
232 * \brief Sets the number of parallel threads to use
233 * for the user contexts.
235 * This function should be called before initializing SIMIX.
236 * A value of 1 means no parallelism (1 thread only).
237 * If the value is greater than 1, the thread support must be enabled.
239 * \param nb_threads the number of threads to use
241 void SIMIX_context_set_nthreads(int nb_threads) {
243 nb_threads = xbt_os_get_numcores();
244 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
247 if (nb_threads > 1) {
248 #ifndef CONTEXT_THREADS
249 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
252 smx_parallel_contexts = nb_threads;
256 * \brief Returns the threshold above which user processes are run in parallel.
258 * If the number of threads is set to 1, there is no parallelism and this
259 * threshold has no effect.
261 * \return when the number of user processes ready to run is above
262 * this threshold, they are run in parallel
264 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
265 return smx_parallel_threshold;
269 * \brief Sets the threshold above which user processes are run in parallel.
271 * If the number of threads is set to 1, there is no parallelism and this
272 * threshold has no effect.
274 * \param threshold when the number of user processes ready to run is above
275 * this threshold, they are run in parallel
277 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
278 smx_parallel_threshold = threshold;
282 * \brief Returns the synchronization mode used when processes are run in
284 * \return how threads are synchronized if processes are run in parallel
286 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
287 return smx_parallel_synchronization_mode;
291 * \brief Sets the synchronization mode to use when processes are run in
293 * \param mode how to synchronize threads if processes are run in parallel
295 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
296 smx_parallel_synchronization_mode = mode;
300 * \brief Returns the current context of this thread.
301 * \return the current context of this thread
303 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
305 if (SIMIX_context_is_parallel()) {
306 #ifdef HAVE_THREAD_LOCAL_STORAGE
307 return smx_current_context_parallel;
309 return xbt_os_thread_get_specific(smx_current_context_key);
313 return smx_current_context_serial;
318 * \brief Sets the current context of this thread.
319 * \param context the context to set
321 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
323 if (SIMIX_context_is_parallel()) {
324 #ifdef HAVE_THREAD_LOCAL_STORAGE
325 smx_current_context_parallel = context;
327 xbt_os_thread_set_specific(smx_current_context_key, context);
331 smx_current_context_serial = context;