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/config.hpp>
13 #include <xbt/range.hpp>
15 #include "src/internal_config.h"
18 #include "xbt/xbt_os_thread.h"
19 #include "smx_private.h"
20 #include "simgrid/sg_config.h"
21 #include "src/internal_config.h"
22 #include "simgrid/modelchecker.h"
33 #define _aligned_malloc __mingw_aligned_malloc
34 #define _aligned_free __mingw_aligned_free
38 # include <valgrind/valgrind.h>
41 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
43 static std::pair<const char*, simgrid::simix::ContextFactoryInitializer> context_factories[] = {
45 { "raw", &simgrid::simix::raw_factory },
47 #if HAVE_UCONTEXT_CONTEXTS
48 { "ucontext", &simgrid::simix::sysv_factory },
50 #if HAVE_BOOST_CONTEXTS
51 { "boost", &simgrid::simix::boost_factory },
53 #if HAVE_THREAD_CONTEXTS
54 { "thread", &simgrid::simix::thread_factory },
58 static_assert(sizeof(context_factories) != 0,
59 "No context factories are enabled for this build");
61 // Create the list of possible contexts:
63 std::string contexts_list()
66 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
67 for (std::size_t i = 1; i != n; ++i) {
69 res += context_factories[i].first;
74 static simgrid::config::Flag<std::string> context_factory_name(
76 (std::string("Possible values: ")+contexts_list()).c_str(),
77 context_factories[0].first);
79 int smx_context_stack_size;
80 int smx_context_stack_size_was_set = 0;
81 int smx_context_guard_size;
82 int smx_context_guard_size_was_set = 0;
83 #if HAVE_THREAD_LOCAL_STORAGE
84 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
86 static xbt_os_thread_key_t smx_current_context_key = 0;
88 static smx_context_t smx_current_context_serial;
89 static int smx_parallel_contexts = 1;
90 static int smx_parallel_threshold = 2;
91 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
94 void invalid_context_factory()
96 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
98 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
100 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
102 #if HAVE_UCONTEXT_CONTEXTS
103 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
105 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
107 #if HAVE_BOOST_CONTEXTS
108 XBT_ERROR(" boost: this uses the boost libraries context implementation");
110 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
112 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
113 xbt_die("Please use a valid factory.");
117 * This function is called by SIMIX_global_init() to initialize the context module.
119 void SIMIX_context_mod_init(void)
121 #if HAVE_THREAD_CONTEXTS && !HAVE_THREAD_LOCAL_STORAGE
122 /* the __thread storage class is not available on this platform:
123 * use getspecific/setspecific instead to store the current context in each thread */
124 xbt_os_thread_key_create(&smx_current_context_key);
126 if (simix_global->context_factory)
128 /* select the context factory to use to create the contexts */
129 if (simgrid::simix::factory_initializer) { // Give Java a chance to hijack the factory mechanism
130 simix_global->context_factory = simgrid::simix::factory_initializer();
133 /* use the factory specified by --cfg=contexts/factory:value */
134 for (auto const& factory : context_factories)
135 if (context_factory_name == factory.first) {
136 simix_global->context_factory = factory.second();
139 if (simix_global->context_factory == nullptr)
140 invalid_context_factory();
144 * This function is called by SIMIX_clean() to finalize the context module.
146 void SIMIX_context_mod_exit(void)
148 delete simix_global->context_factory;
149 simix_global->context_factory = nullptr;
152 void *SIMIX_context_stack_new(void)
156 /* FIXME: current code for stack overflow protection assumes that stacks are
157 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
158 * after the stack when PTH_STACKGROWTH == 1. */
160 if (smx_context_guard_size > 0 && !MC_is_active()) {
162 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
163 static int warned_once = 0;
165 XBT_WARN("Stack overflow protection is known to be broken on your system. Either stack grows upwards, or it was not even tested properly.");
170 size_t size = smx_context_stack_size + smx_context_guard_size;
172 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
173 * pointer returned by xbt_malloc0. */
174 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
175 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
176 *((void **)stack - 1) = alloc;
177 #elif !defined(_WIN32)
178 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
179 xbt_die("Failed to allocate stack.");
181 stack = _aligned_malloc(size, xbt_pagesize);
185 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
186 xbt_die("Failed to protect stack: %s", strerror(errno));
187 /* This is fatal. We are going to fail at some point when
188 we tryi reusing this. */
191 stack = (char *)stack + smx_context_guard_size;
193 stack = xbt_malloc0(smx_context_stack_size);
197 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
198 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
204 void SIMIX_context_stack_delete(void *stack)
210 unsigned int valgrind_stack_id;
211 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
212 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
216 if (smx_context_guard_size > 0 && !MC_is_active()) {
217 stack = (char *)stack - smx_context_guard_size;
218 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
219 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
220 /* try to pursue anyway */
223 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
224 stack = *((void **)stack - 1);
227 #endif /* not windows */
232 /** @brief Returns whether some parallel threads are used for the user contexts. */
233 int SIMIX_context_is_parallel(void) {
234 return smx_parallel_contexts > 1;
238 * @brief Returns the number of parallel threads used for the user contexts.
239 * \return the number of threads (1 means no parallelism)
241 int SIMIX_context_get_nthreads(void) {
242 return smx_parallel_contexts;
246 * \brief Sets the number of parallel threads to use
247 * for the user contexts.
249 * This function should be called before initializing SIMIX.
250 * A value of 1 means no parallelism (1 thread only).
251 * If the value is greater than 1, the thread support must be enabled.
253 * \param nb_threads the number of threads to use
255 void SIMIX_context_set_nthreads(int nb_threads) {
257 nb_threads = xbt_os_get_numcores();
258 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
260 #if !HAVE_THREAD_CONTEXTS
261 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
263 smx_parallel_contexts = nb_threads;
267 * \brief Returns the threshold above which user processes are run in parallel.
269 * If the number of threads is set to 1, there is no parallelism and this
270 * threshold has no effect.
272 * \return when the number of user processes ready to run is above
273 * this threshold, they are run in parallel
275 int SIMIX_context_get_parallel_threshold(void) {
276 return smx_parallel_threshold;
280 * \brief Sets the threshold above which user processes are run in parallel.
282 * If the number of threads is set to 1, there is no parallelism and this
283 * threshold has no effect.
285 * \param threshold when the number of user processes ready to run is above
286 * this threshold, they are run in parallel
288 void SIMIX_context_set_parallel_threshold(int threshold) {
289 smx_parallel_threshold = threshold;
293 * \brief Returns the synchronization mode used when processes are run in
295 * \return how threads are synchronized if processes are run in parallel
297 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
298 return smx_parallel_synchronization_mode;
302 * \brief Sets the synchronization mode to use when processes are run in
304 * \param mode how to synchronize threads if processes are run in parallel
306 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
307 smx_parallel_synchronization_mode = mode;
311 * \brief Returns the current context of this thread.
312 * \return the current context of this thread
314 smx_context_t SIMIX_context_get_current(void)
316 if (SIMIX_context_is_parallel()) {
317 #if HAVE_THREAD_LOCAL_STORAGE
318 return smx_current_context_parallel;
320 return xbt_os_thread_get_specific(smx_current_context_key);
324 return smx_current_context_serial;
329 * \brief Sets the current context of this thread.
330 * \param context the context to set
332 void SIMIX_context_set_current(smx_context_t context)
334 if (SIMIX_context_is_parallel()) {
335 #if HAVE_THREAD_LOCAL_STORAGE
336 smx_current_context_parallel = context;
338 xbt_os_thread_set_specific(smx_current_context_key, context);
342 smx_current_context_serial = context;