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 "smx_private.hpp"
15 #include "simgrid/sg_config.h"
16 #include "src/internal_config.h"
17 #include "simgrid/modelchecker.h"
28 #define _aligned_malloc __mingw_aligned_malloc
29 #define _aligned_free __mingw_aligned_free
32 #ifdef HAVE_VALGRIND_VALGRIND_H
33 # include <valgrind/valgrind.h>
36 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
37 "Context switching mechanism");
39 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
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(HAVE_THREAD_CONTEXTS) && !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 (simgrid::simix::factory_initializer)
67 simix_global->context_factory = simgrid::simix::factory_initializer();
68 else { /* use the factory specified by --cfg=contexts/factory:value */
69 #if defined(HAVE_THREAD_CONTEXTS)
70 if (!strcmp(smx_context_factory_name, "thread"))
71 simix_global->context_factory = simgrid::simix::thread_factory();
75 #ifdef HAVE_UCONTEXT_CONTEXTS
76 else if (!strcmp(smx_context_factory_name, "ucontext"))
77 simix_global->context_factory = simgrid::simix::sysv_factory();
79 #ifdef HAVE_RAW_CONTEXTS
80 else if (!strcmp(smx_context_factory_name, "raw"))
81 simix_global->context_factory = simgrid::simix::raw_factory();
83 #ifdef HAVE_BOOST_CONTEXTS
84 else if (!strcmp(smx_context_factory_name, "boost"))
85 simix_global->context_factory = simgrid::simix::boost_factory();
88 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
89 #ifdef HAVE_RAW_CONTEXTS
90 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
92 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
94 #ifdef HAVE_UCONTEXT_CONTEXTS
95 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
97 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
99 #ifdef HAVE_BOOST_CONTEXTS
100 XBT_ERROR(" boost: this uses the boost libraries context implementation");
102 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
104 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
105 xbt_die("Please use a valid factory.");
112 * This function is called by SIMIX_clean() to finalize the context module.
114 void SIMIX_context_mod_exit(void)
116 delete simix_global->context_factory;
117 simix_global->context_factory = nullptr;
118 xbt_dict_remove((xbt_dict_t) _sg_cfg_set,"contexts/factory");
121 void *SIMIX_context_stack_new(void)
125 /* FIXME: current code for stack overflow protection assumes that stacks are
126 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
127 * after the stack when PTH_STACKGROWTH == 1. */
129 if (smx_context_guard_size > 0 && !MC_is_active()) {
131 #if defined(_XBT_WIN32) || (PTH_STACKGROWTH != -1)
132 static int warned_once = 0;
134 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).",
140 size_t size = smx_context_stack_size + smx_context_guard_size;
142 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
143 * pointer returned by xbt_malloc0. */
144 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
145 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
146 *((void **)stack - 1) = alloc;
147 #elif !defined(_XBT_WIN32)
148 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
149 xbt_die("Failed to allocate stack.");
151 stack = _aligned_malloc(size, xbt_pagesize);
155 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
156 xbt_die("Failed to protect stack: %s", strerror(errno));
157 /* This is fatal. We are going to fail at some point when
158 we tryi reusing this. */
161 stack = (char *)stack + smx_context_guard_size;
163 stack = xbt_malloc0(smx_context_stack_size);
166 #ifdef HAVE_VALGRIND_VALGRIND_H
167 unsigned int valgrind_stack_id =
168 VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
169 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id,
170 sizeof valgrind_stack_id);
176 void SIMIX_context_stack_delete(void *stack)
181 #ifdef HAVE_VALGRIND_VALGRIND_H
182 unsigned int valgrind_stack_id;
183 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size,
184 sizeof valgrind_stack_id);
185 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
189 if (smx_context_guard_size > 0 && !MC_is_active()) {
190 stack = (char *)stack - smx_context_guard_size;
191 if (mprotect(stack, smx_context_guard_size,
192 PROT_READ | PROT_WRITE) == -1) {
193 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
194 /* try to pursue anyway */
197 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
198 stack = *((void **)stack - 1);
207 * \brief Returns whether some parallel threads are used
208 * for the user contexts.
209 * \return 1 if parallelism is used
211 int SIMIX_context_is_parallel(void) {
212 return smx_parallel_contexts > 1;
216 * \brief Returns the number of parallel threads used
217 * for the user contexts.
218 * \return the number of threads (1 means no parallelism)
220 int SIMIX_context_get_nthreads(void) {
221 return smx_parallel_contexts;
225 * \brief Sets the number of parallel threads to use
226 * for the user contexts.
228 * This function should be called before initializing SIMIX.
229 * A value of 1 means no parallelism (1 thread only).
230 * If the value is greater than 1, the thread support must be enabled.
232 * \param nb_threads the number of threads to use
234 void SIMIX_context_set_nthreads(int nb_threads) {
236 nb_threads = xbt_os_get_numcores();
237 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
240 if (nb_threads > 1) {
241 #ifndef HAVE_THREAD_CONTEXTS
242 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
245 smx_parallel_contexts = nb_threads;
249 * \brief Returns the threshold above which user processes are run in parallel.
251 * If the number of threads is set to 1, there is no parallelism and this
252 * threshold has no effect.
254 * \return when the number of user processes ready to run is above
255 * this threshold, they are run in parallel
257 int SIMIX_context_get_parallel_threshold(void) {
258 return smx_parallel_threshold;
262 * \brief Sets the threshold above which user processes are run in parallel.
264 * If the number of threads is set to 1, there is no parallelism and this
265 * threshold has no effect.
267 * \param threshold when the number of user processes ready to run is above
268 * this threshold, they are run in parallel
270 void SIMIX_context_set_parallel_threshold(int threshold) {
271 smx_parallel_threshold = threshold;
275 * \brief Returns the synchronization mode used when processes are run in
277 * \return how threads are synchronized if processes are run in parallel
279 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
280 return smx_parallel_synchronization_mode;
284 * \brief Sets the synchronization mode to use when processes are run in
286 * \param mode how to synchronize threads if processes are run in parallel
288 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
289 smx_parallel_synchronization_mode = mode;
293 * \brief Returns the current context of this thread.
294 * \return the current context of this thread
296 smx_context_t SIMIX_context_get_current(void)
298 if (SIMIX_context_is_parallel()) {
299 #ifdef HAVE_THREAD_LOCAL_STORAGE
300 return smx_current_context_parallel;
302 return xbt_os_thread_get_specific(smx_current_context_key);
306 return smx_current_context_serial;
311 * \brief Sets the current context of this thread.
312 * \param context the context to set
314 void SIMIX_context_set_current(smx_context_t context)
316 if (SIMIX_context_is_parallel()) {
317 #ifdef HAVE_THREAD_LOCAL_STORAGE
318 smx_current_context_parallel = context;
320 xbt_os_thread_set_specific(smx_current_context_key, context);
324 smx_current_context_serial = context;