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. */
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"
26 #define _aligned_malloc __mingw_aligned_malloc
27 #define _aligned_free __mingw_aligned_free
30 #if defined(_XBT_WIN32)
34 #ifdef HAVE_VALGRIND_VALGRIND_H
35 # include <valgrind/valgrind.h>
38 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
39 "Context switching mechanism");
41 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
42 smx_ctx_factory_initializer_t smx_factory_initializer_to_use = NULL;
43 int smx_context_stack_size;
44 int smx_context_stack_size_was_set = 0;
45 int smx_context_guard_size;
46 int smx_context_guard_size_was_set = 0;
47 #ifdef HAVE_THREAD_LOCAL_STORAGE
48 static __thread smx_context_t smx_current_context_parallel;
50 static xbt_os_thread_key_t smx_current_context_key = 0;
52 static smx_context_t smx_current_context_serial;
53 static int smx_parallel_contexts = 1;
54 static int smx_parallel_threshold = 2;
55 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
58 * This function is called by SIMIX_global_init() to initialize the context module.
60 void SIMIX_context_mod_init(void)
62 #if defined(CONTEXT_THREADS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
63 /* the __thread storage class is not available on this platform:
64 * use getspecific/setspecific instead to store the current context in each thread */
65 xbt_os_thread_key_create(&smx_current_context_key);
67 if (!simix_global->context_factory) {
68 /* select the context factory to use to create the contexts */
69 if (smx_factory_initializer_to_use) {
70 smx_factory_initializer_to_use(&simix_global->context_factory);
72 else { /* use the factory specified by --cfg=contexts/factory:value */
75 if (!strcmp(smx_context_factory_name, "thread")) {
76 /* use os threads (either pthreads or windows ones) */
77 SIMIX_ctx_thread_factory_init(&simix_global->context_factory);
79 #ifdef CONTEXT_UCONTEXT
80 else if (!strcmp(smx_context_factory_name, "ucontext")) {
82 SIMIX_ctx_sysv_factory_init(&simix_global->context_factory);
86 else if (!strcmp(smx_context_factory_name, "raw")) {
87 /* use raw contexts */
88 SIMIX_ctx_raw_factory_init(&simix_global->context_factory);
91 #ifdef HAVE_BOOST_CONTEXT
92 else if (!strcmp(smx_context_factory_name, "boost")) {
93 /* use Boost.Context */
94 SIMIX_ctx_boost_factory_init(&simix_global->context_factory);
98 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
100 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
102 XBT_ERROR(" (raw contexts are disabled at compilation time on this machine -- check configure logs for details)");
104 #ifdef CONTEXT_UCONTEXT
105 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
107 XBT_ERROR(" (ucontext is disabled at compilation time on this machine -- check configure logs for details)");
109 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
110 xbt_die("Please use a valid factory.");
117 * This function is called by SIMIX_clean() to finalize the context module.
119 void SIMIX_context_mod_exit(void)
121 if (simix_global->context_factory) {
122 smx_pfn_context_factory_finalize_t finalize_factory;
124 /* finalize the context factory */
125 finalize_factory = simix_global->context_factory->finalize;
126 finalize_factory(&simix_global->context_factory);
128 xbt_dict_remove((xbt_dict_t) _sg_cfg_set,"contexts/factory");
131 void *SIMIX_context_stack_new(void)
135 /* FIXME: current code for stack overflow protection assumes that stacks are
136 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
137 * after the stack when PTH_STACKGROWTH == 1. */
139 if (smx_context_guard_size > 0 && !MC_is_active()) {
141 #if defined(_XBT_WIN32) || (PTH_STACKGROWTH != -1)
142 static int warned_once = 0;
144 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).",
150 size_t size = smx_context_stack_size + smx_context_guard_size;
152 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
153 * pointer returned by xbt_malloc0. */
154 char *alloc = xbt_malloc0(size + xbt_pagesize);
155 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
156 *((void **)stack - 1) = alloc;
157 #elif !defined(_XBT_WIN32)
158 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
159 xbt_die("Failed to allocate stack.");
161 stack = _aligned_malloc(size, xbt_pagesize);
165 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
166 xbt_die("Failed to protect stack: %s", strerror(errno));
167 /* This is fatal. We are going to fail at some point when
168 we tryi reusing this. */
171 stack = (char *)stack + smx_context_guard_size;
173 stack = xbt_malloc0(smx_context_stack_size);
176 #ifdef HAVE_VALGRIND_VALGRIND_H
177 unsigned int valgrind_stack_id =
178 VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
179 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id,
180 sizeof valgrind_stack_id);
186 void SIMIX_context_stack_delete(void *stack)
191 #ifdef HAVE_VALGRIND_VALGRIND_H
192 unsigned int valgrind_stack_id;
193 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size,
194 sizeof valgrind_stack_id);
195 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
199 if (smx_context_guard_size > 0 && !MC_is_active()) {
200 stack = (char *)stack - smx_context_guard_size;
201 if (mprotect(stack, smx_context_guard_size,
202 PROT_READ | PROT_WRITE) == -1) {
203 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
204 /* try to pursue anyway */
207 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
208 stack = *((void **)stack - 1);
217 * \brief Returns whether some parallel threads are used
218 * for the user contexts.
219 * \return 1 if parallelism is used
221 XBT_INLINE int SIMIX_context_is_parallel(void) {
222 return smx_parallel_contexts > 1;
226 * \brief Returns the number of parallel threads used
227 * for the user contexts.
228 * \return the number of threads (1 means no parallelism)
230 XBT_INLINE int SIMIX_context_get_nthreads(void) {
231 return smx_parallel_contexts;
235 * \brief Sets the number of parallel threads to use
236 * for the user contexts.
238 * This function should be called before initializing SIMIX.
239 * A value of 1 means no parallelism (1 thread only).
240 * If the value is greater than 1, the thread support must be enabled.
242 * \param nb_threads the number of threads to use
244 void SIMIX_context_set_nthreads(int nb_threads) {
246 nb_threads = xbt_os_get_numcores();
247 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
250 if (nb_threads > 1) {
251 #ifndef CONTEXT_THREADS
252 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
255 smx_parallel_contexts = nb_threads;
259 * \brief Returns the threshold above which user processes are run in parallel.
261 * If the number of threads is set to 1, there is no parallelism and this
262 * threshold has no effect.
264 * \return when the number of user processes ready to run is above
265 * this threshold, they are run in parallel
267 XBT_INLINE int SIMIX_context_get_parallel_threshold(void) {
268 return smx_parallel_threshold;
272 * \brief Sets the threshold above which user processes are run in parallel.
274 * If the number of threads is set to 1, there is no parallelism and this
275 * threshold has no effect.
277 * \param threshold when the number of user processes ready to run is above
278 * this threshold, they are run in parallel
280 XBT_INLINE void SIMIX_context_set_parallel_threshold(int threshold) {
281 smx_parallel_threshold = threshold;
285 * \brief Returns the synchronization mode used when processes are run in
287 * \return how threads are synchronized if processes are run in parallel
289 XBT_INLINE e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
290 return smx_parallel_synchronization_mode;
294 * \brief Sets the synchronization mode to use when processes are run in
296 * \param mode how to synchronize threads if processes are run in parallel
298 XBT_INLINE void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
299 smx_parallel_synchronization_mode = mode;
303 * \brief Returns the current context of this thread.
304 * \return the current context of this thread
306 XBT_INLINE smx_context_t SIMIX_context_get_current(void)
308 if (SIMIX_context_is_parallel()) {
309 #ifdef HAVE_THREAD_LOCAL_STORAGE
310 return smx_current_context_parallel;
312 return xbt_os_thread_get_specific(smx_current_context_key);
316 return smx_current_context_serial;
321 * \brief Sets the current context of this thread.
322 * \param context the context to set
324 XBT_INLINE void SIMIX_context_set_current(smx_context_t context)
326 if (SIMIX_context_is_parallel()) {
327 #ifdef HAVE_THREAD_LOCAL_STORAGE
328 smx_current_context_parallel = context;
330 xbt_os_thread_set_specific(smx_current_context_key, context);
334 smx_current_context_serial = context;