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 { "thread", &simgrid::kernel::context::thread_factory },
46 static_assert(sizeof(context_factories) != 0, "No context factories are enabled for this build");
48 // Create the list of possible contexts:
50 std::string contexts_list()
53 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
54 for (std::size_t i = 1; i != n; ++i) {
56 res += context_factories[i].first;
61 static simgrid::config::Flag<std::string> context_factory_name(
63 (std::string("Possible values: ")+contexts_list()).c_str(),
64 context_factories[0].first);
66 unsigned smx_context_stack_size;
67 int smx_context_stack_size_was_set = 0;
68 unsigned smx_context_guard_size;
69 int smx_context_guard_size_was_set = 0;
70 static thread_local smx_context_t smx_current_context_parallel;
71 static smx_context_t smx_current_context_serial;
72 static int smx_parallel_contexts = 1;
73 static int smx_parallel_threshold = 2;
74 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
77 * This function is called by SIMIX_global_init() to initialize the context module.
79 void SIMIX_context_mod_init()
81 xbt_assert(simix_global->context_factory == nullptr);
83 smx_context_stack_size_was_set = not simgrid::config::is_default("contexts/stack-size");
84 smx_context_guard_size_was_set = not simgrid::config::is_default("contexts/guard-size");
86 #if HAVE_SMPI && (defined(__APPLE__) || defined(__NetBSD__))
87 std::string priv = simgrid::config::get_value<std::string>("smpi/privatization");
88 if (context_factory_name == "thread" && (priv == "dlopen" || priv == "yes" || priv == "default" || priv == "1")) {
89 XBT_WARN("dlopen+thread broken on Apple and BSD. Switching to raw contexts.");
90 context_factory_name = "raw";
94 #if HAVE_SMPI && defined(__FreeBSD__)
95 if (context_factory_name == "thread" && simgrid::config::get_value<std::string>("smpi/privatization") != "no") {
96 XBT_WARN("mmap broken on FreeBSD, but dlopen+thread broken too. Switching to dlopen+raw contexts.");
97 context_factory_name = "raw";
101 /* select the context factory to use to create the contexts */
102 if (simgrid::kernel::context::factory_initializer != nullptr) { // Give Java a chance to hijack the factory mechanism
103 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
106 /* use the factory specified by --cfg=contexts/factory:value */
107 for (auto const& factory : context_factories)
108 if (context_factory_name == factory.first) {
109 simix_global->context_factory = factory.second();
113 if (simix_global->context_factory == nullptr) {
114 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
115 #if HAVE_RAW_CONTEXTS
116 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
118 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
120 #if HAVE_UCONTEXT_CONTEXTS
121 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
123 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
125 #if HAVE_BOOST_CONTEXTS
126 XBT_ERROR(" boost: this uses the boost libraries context implementation");
128 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
130 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
131 xbt_die("Please use a valid factory.");
136 * This function is called by SIMIX_clean() to finalize the context module.
138 void SIMIX_context_mod_exit()
140 delete simix_global->context_factory;
141 simix_global->context_factory = nullptr;
144 void *SIMIX_context_stack_new()
148 if (smx_context_guard_size > 0 && not MC_is_active()) {
150 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
151 xbt_die("Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
153 "Please disable stack guards with --cfg=contexts:guard-size:0");
154 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
155 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
158 size_t size = smx_context_stack_size + smx_context_guard_size;
160 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
161 * pointer returned by xbt_malloc0. */
162 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
163 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
164 *((void **)stack - 1) = alloc;
165 #elif !defined(_WIN32)
166 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
167 xbt_die("Failed to allocate stack.");
169 stack = _aligned_malloc(size, xbt_pagesize);
173 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
175 "Failed to protect stack: %s.\n"
176 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
177 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
178 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more info.",
180 /* This is fatal. We are going to fail at some point when we try reusing this. */
183 stack = (char *)stack + smx_context_guard_size;
185 stack = xbt_malloc0(smx_context_stack_size);
189 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
190 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
196 void SIMIX_context_stack_delete(void *stack)
202 unsigned int valgrind_stack_id;
203 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
204 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
208 if (smx_context_guard_size > 0 && not MC_is_active()) {
209 stack = (char *)stack - smx_context_guard_size;
210 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
211 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
212 /* try to pursue anyway */
215 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
216 stack = *((void **)stack - 1);
219 #endif /* not windows */
224 /** @brief Returns whether some parallel threads are used for the user contexts. */
225 int SIMIX_context_is_parallel() {
226 return smx_parallel_contexts > 1;
230 * @brief Returns the number of parallel threads used for the user contexts.
231 * @return the number of threads (1 means no parallelism)
233 int SIMIX_context_get_nthreads() {
234 return smx_parallel_contexts;
238 * @brief Sets the number of parallel threads to use
239 * for the user contexts.
241 * This function should be called before initializing SIMIX.
242 * A value of 1 means no parallelism (1 thread only).
243 * If the value is greater than 1, the thread support must be enabled.
245 * @param nb_threads the number of threads to use
247 void SIMIX_context_set_nthreads(int nb_threads) {
249 nb_threads = std::thread::hardware_concurrency();
250 XBT_INFO("Auto-setting contexts/nthreads to %d", nb_threads);
252 smx_parallel_contexts = nb_threads;
256 * @brief Returns the threshold above which user processes are run in parallel.
258 * If the number of threads is set to 1, there is no parallelism and this
259 * threshold has no effect.
261 * @return when the number of user processes ready to run is above
262 * this threshold, they are run in parallel
264 int SIMIX_context_get_parallel_threshold() {
265 return smx_parallel_threshold;
269 * @brief Sets the threshold above which user processes are run in parallel.
271 * If the number of threads is set to 1, there is no parallelism and this
272 * threshold has no effect.
274 * @param threshold when the number of user processes ready to run is above
275 * this threshold, they are run in parallel
277 void SIMIX_context_set_parallel_threshold(int threshold) {
278 smx_parallel_threshold = threshold;
282 * @brief Returns the synchronization mode used when processes are run in
284 * @return how threads are synchronized if processes are run in parallel
286 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode() {
287 return smx_parallel_synchronization_mode;
291 * @brief Sets the synchronization mode to use when processes are run in
293 * @param mode how to synchronize threads if processes are run in parallel
295 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
296 smx_parallel_synchronization_mode = mode;
300 * @brief Returns the current context of this thread.
301 * @return the current context of this thread
303 smx_context_t SIMIX_context_get_current()
305 if (SIMIX_context_is_parallel()) {
306 return smx_current_context_parallel;
309 return smx_current_context_serial;
314 * @brief Sets the current context of this thread.
315 * @param context the context to set
317 void SIMIX_context_set_current(smx_context_t context)
319 if (SIMIX_context_is_parallel()) {
320 smx_current_context_parallel = context;
323 smx_current_context_serial = context;