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_H
33 # include <valgrind/valgrind.h>
36 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
38 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
39 int smx_context_stack_size;
40 int smx_context_stack_size_was_set = 0;
41 int smx_context_guard_size;
42 int smx_context_guard_size_was_set = 0;
43 static thread_local smx_context_t smx_current_context_parallel;
44 static smx_context_t smx_current_context_serial;
45 static int smx_parallel_contexts = 1;
46 static int smx_parallel_threshold = 2;
47 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
50 * This function is called by SIMIX_global_init() to initialize the context module.
52 void SIMIX_context_mod_init(void)
54 if (!simix_global->context_factory) {
55 /* select the context factory to use to create the contexts */
56 if (simgrid::simix::factory_initializer)
57 simix_global->context_factory = simgrid::simix::factory_initializer();
58 else { /* use the factory specified by --cfg=contexts/factory:value */
59 #if defined(HAVE_THREAD_CONTEXTS)
60 if (!strcmp(smx_context_factory_name, "thread"))
61 simix_global->context_factory = simgrid::simix::thread_factory();
65 #ifdef HAVE_UCONTEXT_CONTEXTS
66 else if (!strcmp(smx_context_factory_name, "ucontext"))
67 simix_global->context_factory = simgrid::simix::sysv_factory();
69 #ifdef HAVE_RAW_CONTEXTS
70 else if (!strcmp(smx_context_factory_name, "raw"))
71 simix_global->context_factory = simgrid::simix::raw_factory();
73 #ifdef HAVE_BOOST_CONTEXTS
74 else if (!strcmp(smx_context_factory_name, "boost"))
75 simix_global->context_factory = simgrid::simix::boost_factory();
78 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
79 #ifdef HAVE_RAW_CONTEXTS
80 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
82 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
84 #ifdef HAVE_UCONTEXT_CONTEXTS
85 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
87 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
89 #ifdef HAVE_BOOST_CONTEXTS
90 XBT_ERROR(" boost: this uses the boost libraries context implementation");
92 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
94 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
95 xbt_die("Please use a valid factory.");
102 * This function is called by SIMIX_clean() to finalize the context module.
104 void SIMIX_context_mod_exit(void)
106 delete simix_global->context_factory;
107 simix_global->context_factory = nullptr;
110 void *SIMIX_context_stack_new(void)
114 /* FIXME: current code for stack overflow protection assumes that stacks are
115 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
116 * after the stack when PTH_STACKGROWTH == 1. */
118 if (smx_context_guard_size > 0 && !MC_is_active()) {
120 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
121 static int warned_once = 0;
123 XBT_WARN("Stack overflow protection is known to be broken on your system. Either stack grows upwards, or it was not even tested properly.");
128 size_t size = smx_context_stack_size + smx_context_guard_size;
130 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
131 * pointer returned by xbt_malloc0. */
132 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
133 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
134 *((void **)stack - 1) = alloc;
135 #elif !defined(_WIN32)
136 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
137 xbt_die("Failed to allocate stack.");
139 stack = _aligned_malloc(size, xbt_pagesize);
143 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
144 xbt_die("Failed to protect stack: %s", strerror(errno));
145 /* This is fatal. We are going to fail at some point when
146 we tryi reusing this. */
149 stack = (char *)stack + smx_context_guard_size;
151 stack = xbt_malloc0(smx_context_stack_size);
154 #ifdef HAVE_VALGRIND_H
155 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
156 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
162 void SIMIX_context_stack_delete(void *stack)
167 #ifdef HAVE_VALGRIND_H
168 unsigned int valgrind_stack_id;
169 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
170 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
174 if (smx_context_guard_size > 0 && !MC_is_active()) {
175 stack = (char *)stack - smx_context_guard_size;
176 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
177 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
178 /* try to pursue anyway */
181 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
182 stack = *((void **)stack - 1);
185 #endif /* not windows */
190 /** @brief Returns whether some parallel threads are used for the user contexts. */
191 int SIMIX_context_is_parallel(void) {
192 return smx_parallel_contexts > 1;
196 * \brief Returns the number of parallel threads used
197 * for the user contexts.
198 * \return the number of threads (1 means no parallelism)
200 int SIMIX_context_get_nthreads(void) {
201 return smx_parallel_contexts;
205 * \brief Sets the number of parallel threads to use
206 * for the user contexts.
208 * This function should be called before initializing SIMIX.
209 * A value of 1 means no parallelism (1 thread only).
210 * If the value is greater than 1, the thread support must be enabled.
212 * \param nb_threads the number of threads to use
214 void SIMIX_context_set_nthreads(int nb_threads) {
216 nb_threads = xbt_os_get_numcores();
217 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
219 #ifndef HAVE_THREAD_CONTEXTS
220 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
222 smx_parallel_contexts = nb_threads;
226 * \brief Returns the threshold above which user processes are run in parallel.
228 * If the number of threads is set to 1, there is no parallelism and this
229 * threshold has no effect.
231 * \return when the number of user processes ready to run is above
232 * this threshold, they are run in parallel
234 int SIMIX_context_get_parallel_threshold(void) {
235 return smx_parallel_threshold;
239 * \brief Sets the threshold above which user processes are run in parallel.
241 * If the number of threads is set to 1, there is no parallelism and this
242 * threshold has no effect.
244 * \param threshold when the number of user processes ready to run is above
245 * this threshold, they are run in parallel
247 void SIMIX_context_set_parallel_threshold(int threshold) {
248 smx_parallel_threshold = threshold;
252 * \brief Returns the synchronization mode used when processes are run in
254 * \return how threads are synchronized if processes are run in parallel
256 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
257 return smx_parallel_synchronization_mode;
261 * \brief Sets the synchronization mode to use when processes are run in
263 * \param mode how to synchronize threads if processes are run in parallel
265 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
266 smx_parallel_synchronization_mode = mode;
270 * \brief Returns the current context of this thread.
271 * \return the current context of this thread
273 smx_context_t SIMIX_context_get_current(void)
275 if (SIMIX_context_is_parallel())
276 return smx_current_context_parallel;
278 return smx_current_context_serial;
282 * \brief Sets the current context of this thread.
283 * \param context the context to set
285 void SIMIX_context_set_current(smx_context_t context)
287 if (SIMIX_context_is_parallel())
288 smx_current_context_parallel = context;
290 smx_current_context_serial = context;