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. */
14 #include <xbt/config.hpp>
16 #include <xbt/range.hpp>
17 #include <xbt/sysdep.h>
19 #include "simgrid/modelchecker.h"
20 #include "simgrid/sg_config.hpp"
21 #include "smx_private.hpp"
22 #include "src/internal_config.h"
24 #include "xbt/xbt_os_thread.h"
34 #define _aligned_malloc __mingw_aligned_malloc
35 #define _aligned_free __mingw_aligned_free
39 # include <valgrind/valgrind.h>
42 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
44 static std::pair<const char*, simgrid::kernel::context::ContextFactoryInitializer> context_factories[] = {
46 { "raw", &simgrid::kernel::context::raw_factory },
48 #if HAVE_UCONTEXT_CONTEXTS
49 { "ucontext", &simgrid::kernel::context::sysv_factory },
51 #if HAVE_BOOST_CONTEXTS
52 { "boost", &simgrid::kernel::context::boost_factory },
54 #if HAVE_THREAD_CONTEXTS
55 { "thread", &simgrid::kernel::context::thread_factory },
59 static_assert(sizeof(context_factories) != 0, "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 unsigned smx_context_stack_size;
80 int smx_context_stack_size_was_set = 0;
81 unsigned smx_context_guard_size;
82 int smx_context_guard_size_was_set = 0;
83 static thread_local smx_context_t smx_current_context_parallel;
84 static smx_context_t smx_current_context_serial;
85 static int smx_parallel_contexts = 1;
86 static int smx_parallel_threshold = 2;
87 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
90 * This function is called by SIMIX_global_init() to initialize the context module.
92 void SIMIX_context_mod_init()
94 xbt_assert(simix_global->context_factory == nullptr);
96 smx_context_stack_size_was_set = not simgrid::config::is_default("contexts/stack-size");
97 smx_context_guard_size_was_set = not simgrid::config::is_default("contexts/guard-size");
99 #if HAVE_SMPI && (defined(__APPLE__) || defined(__NetBSD__))
100 std::string priv = simgrid::config::get_value<std::string>("smpi/privatization");
101 if (context_factory_name == "thread" && (priv == "dlopen" || priv == "yes" || priv == "default" || priv == "1")) {
102 XBT_WARN("dlopen+thread broken on Apple and BSD. Switching to raw contexts.");
103 context_factory_name = "raw";
107 #if HAVE_SMPI && defined(__FreeBSD__)
108 if (context_factory_name == "thread" && simgrid::config::get_value<std::string>("smpi/privatization") != "no") {
109 XBT_WARN("mmap broken on FreeBSD, but dlopen+thread broken too. Switching to dlopen+raw contexts.");
110 context_factory_name = "raw";
114 /* select the context factory to use to create the contexts */
115 if (simgrid::kernel::context::factory_initializer) { // Give Java a chance to hijack the factory mechanism
116 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
119 /* use the factory specified by --cfg=contexts/factory:value */
120 for (auto const& factory : context_factories)
121 if (context_factory_name == factory.first) {
122 simix_global->context_factory = factory.second();
126 if (simix_global->context_factory == nullptr) {
127 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
128 #if HAVE_RAW_CONTEXTS
129 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
131 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
133 #if HAVE_UCONTEXT_CONTEXTS
134 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
136 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
138 #if HAVE_BOOST_CONTEXTS
139 XBT_ERROR(" boost: this uses the boost libraries context implementation");
141 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
143 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
144 xbt_die("Please use a valid factory.");
149 * This function is called by SIMIX_clean() to finalize the context module.
151 void SIMIX_context_mod_exit()
153 delete simix_global->context_factory;
154 simix_global->context_factory = nullptr;
157 void *SIMIX_context_stack_new()
161 if (smx_context_guard_size > 0 && not MC_is_active()) {
163 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
164 xbt_die("Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
166 "Please disable stack guards with --cfg=contexts:guard-size:0");
167 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
168 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
171 size_t size = smx_context_stack_size + smx_context_guard_size;
173 /* Cannot use posix_memalign when SIMGRID_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) {
188 "Failed to protect stack: %s.\n"
189 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
190 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
191 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more info.",
193 /* This is fatal. We are going to fail at some point when we try reusing this. */
196 stack = (char *)stack + smx_context_guard_size;
198 stack = xbt_malloc0(smx_context_stack_size);
202 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
203 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
209 void SIMIX_context_stack_delete(void *stack)
215 unsigned int valgrind_stack_id;
216 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
217 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
221 if (smx_context_guard_size > 0 && not MC_is_active()) {
222 stack = (char *)stack - smx_context_guard_size;
223 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
224 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
225 /* try to pursue anyway */
228 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
229 stack = *((void **)stack - 1);
232 #endif /* not windows */
237 /** @brief Returns whether some parallel threads are used for the user contexts. */
238 int SIMIX_context_is_parallel() {
239 return smx_parallel_contexts > 1;
243 * @brief Returns the number of parallel threads used for the user contexts.
244 * @return the number of threads (1 means no parallelism)
246 int SIMIX_context_get_nthreads() {
247 return smx_parallel_contexts;
251 * @brief Sets the number of parallel threads to use
252 * for the user contexts.
254 * This function should be called before initializing SIMIX.
255 * A value of 1 means no parallelism (1 thread only).
256 * If the value is greater than 1, the thread support must be enabled.
258 * @param nb_threads the number of threads to use
260 void SIMIX_context_set_nthreads(int nb_threads) {
262 nb_threads = xbt_os_get_numcores();
263 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
265 #if !HAVE_THREAD_CONTEXTS
266 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
268 smx_parallel_contexts = nb_threads;
272 * @brief Returns the threshold above which user processes are run in parallel.
274 * If the number of threads is set to 1, there is no parallelism and this
275 * threshold has no effect.
277 * @return when the number of user processes ready to run is above
278 * this threshold, they are run in parallel
280 int SIMIX_context_get_parallel_threshold() {
281 return smx_parallel_threshold;
285 * @brief Sets the threshold above which user processes are run in parallel.
287 * If the number of threads is set to 1, there is no parallelism and this
288 * threshold has no effect.
290 * @param threshold when the number of user processes ready to run is above
291 * this threshold, they are run in parallel
293 void SIMIX_context_set_parallel_threshold(int threshold) {
294 smx_parallel_threshold = threshold;
298 * @brief Returns the synchronization mode used when processes are run in
300 * @return how threads are synchronized if processes are run in parallel
302 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode() {
303 return smx_parallel_synchronization_mode;
307 * @brief Sets the synchronization mode to use when processes are run in
309 * @param mode how to synchronize threads if processes are run in parallel
311 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
312 smx_parallel_synchronization_mode = mode;
316 * @brief Returns the current context of this thread.
317 * @return the current context of this thread
319 smx_context_t SIMIX_context_get_current()
321 if (SIMIX_context_is_parallel()) {
322 return smx_current_context_parallel;
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 smx_current_context_parallel = context;
339 smx_current_context_serial = context;