1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2018. The SimGrid Team. All rights reserved. */
5 /* This program is free software; you can redistribute it and/or modify it
6 * under the terms of the license (GNU LGPL) which comes with this package. */
8 #include "simgrid/modelchecker.h"
9 #include "src/internal_config.h"
10 #include "src/simix/smx_private.hpp"
11 #include "xbt/config.hpp"
23 #define _aligned_malloc __mingw_aligned_malloc
24 #define _aligned_free __mingw_aligned_free
28 # include <valgrind/valgrind.h>
31 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
33 static std::pair<const char*, simgrid::kernel::context::ContextFactoryInitializer> context_factories[] = {
35 { "raw", &simgrid::kernel::context::raw_factory },
37 #if HAVE_UCONTEXT_CONTEXTS
38 { "ucontext", &simgrid::kernel::context::sysv_factory },
40 #if HAVE_BOOST_CONTEXTS
41 { "boost", &simgrid::kernel::context::boost_factory },
43 #if HAVE_THREAD_CONTEXTS
44 { "thread", &simgrid::kernel::context::thread_factory },
48 static_assert(sizeof(context_factories) != 0, "No context factories are enabled for this build");
50 // Create the list of possible contexts:
52 std::string contexts_list()
55 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
56 for (std::size_t i = 1; i != n; ++i) {
58 res += context_factories[i].first;
63 static simgrid::config::Flag<std::string> context_factory_name(
65 (std::string("Possible values: ")+contexts_list()).c_str(),
66 context_factories[0].first);
68 unsigned smx_context_stack_size;
69 int smx_context_stack_size_was_set = 0;
70 unsigned smx_context_guard_size;
71 int smx_context_guard_size_was_set = 0;
72 static thread_local smx_context_t smx_current_context_parallel;
73 static smx_context_t smx_current_context_serial;
74 static int smx_parallel_contexts = 1;
75 static int smx_parallel_threshold = 2;
76 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
79 * This function is called by SIMIX_global_init() to initialize the context module.
81 void SIMIX_context_mod_init()
83 xbt_assert(simix_global->context_factory == nullptr);
85 smx_context_stack_size_was_set = not simgrid::config::is_default("contexts/stack-size");
86 smx_context_guard_size_was_set = not simgrid::config::is_default("contexts/guard-size");
88 #if HAVE_SMPI && (defined(__APPLE__) || defined(__NetBSD__))
89 std::string priv = simgrid::config::get_value<std::string>("smpi/privatization");
90 if (context_factory_name == "thread" && (priv == "dlopen" || priv == "yes" || priv == "default" || priv == "1")) {
91 XBT_WARN("dlopen+thread broken on Apple and BSD. Switching to raw contexts.");
92 context_factory_name = "raw";
96 #if HAVE_SMPI && defined(__FreeBSD__)
97 if (context_factory_name == "thread" && simgrid::config::get_value<std::string>("smpi/privatization") != "no") {
98 XBT_WARN("mmap broken on FreeBSD, but dlopen+thread broken too. Switching to dlopen+raw contexts.");
99 context_factory_name = "raw";
103 /* select the context factory to use to create the contexts */
104 if (simgrid::kernel::context::factory_initializer != nullptr) { // Give Java a chance to hijack the factory mechanism
105 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
108 /* use the factory specified by --cfg=contexts/factory:value */
109 for (auto const& factory : context_factories)
110 if (context_factory_name == factory.first) {
111 simix_global->context_factory = factory.second();
115 if (simix_global->context_factory == nullptr) {
116 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
117 #if HAVE_RAW_CONTEXTS
118 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
120 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
122 #if HAVE_UCONTEXT_CONTEXTS
123 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
125 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
127 #if HAVE_BOOST_CONTEXTS
128 XBT_ERROR(" boost: this uses the boost libraries context implementation");
130 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
132 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
133 xbt_die("Please use a valid factory.");
138 * This function is called by SIMIX_clean() to finalize the context module.
140 void SIMIX_context_mod_exit()
142 delete simix_global->context_factory;
143 simix_global->context_factory = nullptr;
146 void *SIMIX_context_stack_new()
150 if (smx_context_guard_size > 0 && not MC_is_active()) {
152 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
153 xbt_die("Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
155 "Please disable stack guards with --cfg=contexts:guard-size:0");
156 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
157 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
160 size_t size = smx_context_stack_size + smx_context_guard_size;
162 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
163 * pointer returned by xbt_malloc0. */
164 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
165 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
166 *((void **)stack - 1) = alloc;
167 #elif !defined(_WIN32)
168 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
169 xbt_die("Failed to allocate stack.");
171 stack = _aligned_malloc(size, xbt_pagesize);
175 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
177 "Failed to protect stack: %s.\n"
178 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
179 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
180 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more info.",
182 /* This is fatal. We are going to fail at some point when we try reusing this. */
185 stack = (char *)stack + smx_context_guard_size;
187 stack = xbt_malloc0(smx_context_stack_size);
191 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
192 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
198 void SIMIX_context_stack_delete(void *stack)
204 unsigned int valgrind_stack_id;
205 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
206 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
210 if (smx_context_guard_size > 0 && not MC_is_active()) {
211 stack = (char *)stack - smx_context_guard_size;
212 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
213 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
214 /* try to pursue anyway */
217 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
218 stack = *((void **)stack - 1);
221 #endif /* not windows */
226 /** @brief Returns whether some parallel threads are used for the user contexts. */
227 int SIMIX_context_is_parallel() {
228 return smx_parallel_contexts > 1;
232 * @brief Returns the number of parallel threads used for the user contexts.
233 * @return the number of threads (1 means no parallelism)
235 int SIMIX_context_get_nthreads() {
236 return smx_parallel_contexts;
240 * @brief Sets the number of parallel threads to use
241 * for the user contexts.
243 * This function should be called before initializing SIMIX.
244 * A value of 1 means no parallelism (1 thread only).
245 * If the value is greater than 1, the thread support must be enabled.
247 * @param nb_threads the number of threads to use
249 void SIMIX_context_set_nthreads(int nb_threads) {
251 nb_threads = std::thread::hardware_concurrency();
252 XBT_INFO("Auto-setting contexts/nthreads to %d", nb_threads);
254 #if !HAVE_THREAD_CONTEXTS
255 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
257 smx_parallel_contexts = nb_threads;
261 * @brief Returns the threshold above which user processes are run in parallel.
263 * If the number of threads is set to 1, there is no parallelism and this
264 * threshold has no effect.
266 * @return when the number of user processes ready to run is above
267 * this threshold, they are run in parallel
269 int SIMIX_context_get_parallel_threshold() {
270 return smx_parallel_threshold;
274 * @brief Sets the threshold above which user processes are run in parallel.
276 * If the number of threads is set to 1, there is no parallelism and this
277 * threshold has no effect.
279 * @param threshold when the number of user processes ready to run is above
280 * this threshold, they are run in parallel
282 void SIMIX_context_set_parallel_threshold(int threshold) {
283 smx_parallel_threshold = threshold;
287 * @brief Returns the synchronization mode used when processes are run in
289 * @return how threads are synchronized if processes are run in parallel
291 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode() {
292 return smx_parallel_synchronization_mode;
296 * @brief Sets the synchronization mode to use when processes are run in
298 * @param mode how to synchronize threads if processes are run in parallel
300 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
301 smx_parallel_synchronization_mode = mode;
305 * @brief Returns the current context of this thread.
306 * @return the current context of this thread
308 smx_context_t SIMIX_context_get_current()
310 if (SIMIX_context_is_parallel()) {
311 return smx_current_context_parallel;
314 return smx_current_context_serial;
319 * @brief Sets the current context of this thread.
320 * @param context the context to set
322 void SIMIX_context_set_current(smx_context_t context)
324 if (SIMIX_context_is_parallel()) {
325 smx_current_context_parallel = context;
328 smx_current_context_serial = context;