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. */
15 #include <xbt/config.hpp>
17 #include <xbt/range.hpp>
18 #include <xbt/sysdep.h>
20 #include "src/internal_config.h"
23 #include "xbt/xbt_os_thread.h"
24 #include "smx_private.h"
25 #include "simgrid/sg_config.h"
26 #include "src/internal_config.h"
27 #include "simgrid/modelchecker.h"
38 #define _aligned_malloc __mingw_aligned_malloc
39 #define _aligned_free __mingw_aligned_free
43 # include <valgrind/valgrind.h>
46 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
48 static std::pair<const char*, simgrid::kernel::context::ContextFactoryInitializer> context_factories[] = {
50 { "raw", &simgrid::kernel::context::raw_factory },
52 #if HAVE_UCONTEXT_CONTEXTS
53 { "ucontext", &simgrid::kernel::context::sysv_factory },
55 #if HAVE_BOOST_CONTEXTS
56 { "boost", &simgrid::kernel::context::boost_factory },
58 #if HAVE_THREAD_CONTEXTS
59 { "thread", &simgrid::kernel::context::thread_factory },
63 static_assert(sizeof(context_factories) != 0, "No context factories are enabled for this build");
65 // Create the list of possible contexts:
67 std::string contexts_list()
70 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
71 for (std::size_t i = 1; i != n; ++i) {
73 res += context_factories[i].first;
78 static simgrid::config::Flag<std::string> context_factory_name(
80 (std::string("Possible values: ")+contexts_list()).c_str(),
81 context_factories[0].first);
83 int smx_context_stack_size;
84 int smx_context_stack_size_was_set = 0;
85 int smx_context_guard_size;
86 int smx_context_guard_size_was_set = 0;
87 #if HAVE_THREAD_LOCAL_STORAGE
88 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
90 static xbt_os_thread_key_t smx_current_context_key = 0;
92 static smx_context_t smx_current_context_serial;
93 static int smx_parallel_contexts = 1;
94 static int smx_parallel_threshold = 2;
95 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
98 * This function is called by SIMIX_global_init() to initialize the context module.
100 void SIMIX_context_mod_init(void)
102 xbt_assert(simix_global->context_factory == nullptr);
104 #if HAVE_THREAD_CONTEXTS && !HAVE_THREAD_LOCAL_STORAGE
105 /* the __thread storage class is not available on this platform:
106 * use getspecific/setspecific instead to store the current context in each thread */
107 xbt_os_thread_key_create(&smx_current_context_key);
110 /* select the context factory to use to create the contexts */
111 if (simgrid::kernel::context::factory_initializer) { // Give Java a chance to hijack the factory mechanism
112 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
115 /* use the factory specified by --cfg=contexts/factory:value */
116 for (auto const& factory : context_factories)
117 if (context_factory_name == factory.first) {
118 simix_global->context_factory = factory.second();
122 if (simix_global->context_factory == nullptr) {
123 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
124 #if HAVE_RAW_CONTEXTS
125 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
127 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
129 #if HAVE_UCONTEXT_CONTEXTS
130 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
132 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
134 #if HAVE_BOOST_CONTEXTS
135 XBT_ERROR(" boost: this uses the boost libraries context implementation");
137 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
139 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
140 xbt_die("Please use a valid factory.");
145 * This function is called by SIMIX_clean() to finalize the context module.
147 void SIMIX_context_mod_exit(void)
149 delete simix_global->context_factory;
150 simix_global->context_factory = nullptr;
153 void *SIMIX_context_stack_new(void)
157 /* FIXME: current code for stack overflow protection assumes that stacks are
158 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
159 * after the stack when PTH_STACKGROWTH == 1. */
161 if (smx_context_guard_size > 0 && !MC_is_active()) {
163 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
164 static int warned_once = 0;
166 XBT_WARN("Stack overflow protection is known to be broken on your system. Either stack grows upwards, or it was not even tested properly.");
171 size_t size = smx_context_stack_size + smx_context_guard_size;
173 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
174 * pointer returned by xbt_malloc0. */
175 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
176 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
177 *((void **)stack - 1) = alloc;
178 #elif !defined(_WIN32)
179 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
180 xbt_die("Failed to allocate stack.");
182 stack = _aligned_malloc(size, xbt_pagesize);
186 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
187 xbt_die("Failed to protect stack: %s", strerror(errno));
188 /* This is fatal. We are going to fail at some point when
189 we tryi reusing this. */
192 stack = (char *)stack + smx_context_guard_size;
194 stack = xbt_malloc0(smx_context_stack_size);
198 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
199 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
205 void SIMIX_context_stack_delete(void *stack)
211 unsigned int valgrind_stack_id;
212 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
213 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
217 if (smx_context_guard_size > 0 && !MC_is_active()) {
218 stack = (char *)stack - smx_context_guard_size;
219 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
220 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
221 /* try to pursue anyway */
224 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
225 stack = *((void **)stack - 1);
228 #endif /* not windows */
233 /** @brief Returns whether some parallel threads are used for the user contexts. */
234 int SIMIX_context_is_parallel(void) {
235 return smx_parallel_contexts > 1;
239 * @brief Returns the number of parallel threads used for the user contexts.
240 * \return the number of threads (1 means no parallelism)
242 int SIMIX_context_get_nthreads(void) {
243 return smx_parallel_contexts;
247 * \brief Sets the number of parallel threads to use
248 * for the user contexts.
250 * This function should be called before initializing SIMIX.
251 * A value of 1 means no parallelism (1 thread only).
252 * If the value is greater than 1, the thread support must be enabled.
254 * \param nb_threads the number of threads to use
256 void SIMIX_context_set_nthreads(int nb_threads) {
258 nb_threads = xbt_os_get_numcores();
259 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
261 #if !HAVE_THREAD_CONTEXTS
262 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
264 smx_parallel_contexts = nb_threads;
268 * \brief Returns the threshold above which user processes are run in parallel.
270 * If the number of threads is set to 1, there is no parallelism and this
271 * threshold has no effect.
273 * \return when the number of user processes ready to run is above
274 * this threshold, they are run in parallel
276 int SIMIX_context_get_parallel_threshold(void) {
277 return smx_parallel_threshold;
281 * \brief Sets the threshold above which user processes are run in parallel.
283 * If the number of threads is set to 1, there is no parallelism and this
284 * threshold has no effect.
286 * \param threshold when the number of user processes ready to run is above
287 * this threshold, they are run in parallel
289 void SIMIX_context_set_parallel_threshold(int threshold) {
290 smx_parallel_threshold = threshold;
294 * \brief Returns the synchronization mode used when processes are run in
296 * \return how threads are synchronized if processes are run in parallel
298 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
299 return smx_parallel_synchronization_mode;
303 * \brief Sets the synchronization mode to use when processes are run in
305 * \param mode how to synchronize threads if processes are run in parallel
307 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
308 smx_parallel_synchronization_mode = mode;
312 * \brief Returns the current context of this thread.
313 * \return the current context of this thread
315 smx_context_t SIMIX_context_get_current(void)
317 if (SIMIX_context_is_parallel()) {
318 #if HAVE_THREAD_LOCAL_STORAGE
319 return smx_current_context_parallel;
321 return xbt_os_thread_get_specific(smx_current_context_key);
325 return smx_current_context_serial;
330 * \brief Sets the current context of this thread.
331 * \param context the context to set
333 void SIMIX_context_set_current(smx_context_t context)
335 if (SIMIX_context_is_parallel()) {
336 #if HAVE_THREAD_LOCAL_STORAGE
337 smx_current_context_parallel = context;
339 xbt_os_thread_set_specific(smx_current_context_key, context);
343 smx_current_context_serial = context;