1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2017. 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.h"
21 #include "smx_private.hpp"
22 #include "src/internal_config.h"
25 #include "xbt/xbt_os_thread.h"
35 #define _aligned_malloc __mingw_aligned_malloc
36 #define _aligned_free __mingw_aligned_free
40 # include <valgrind/valgrind.h>
43 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
45 static std::pair<const char*, simgrid::kernel::context::ContextFactoryInitializer> context_factories[] = {
47 { "raw", &simgrid::kernel::context::raw_factory },
49 #if HAVE_UCONTEXT_CONTEXTS
50 { "ucontext", &simgrid::kernel::context::sysv_factory },
52 #if HAVE_BOOST_CONTEXTS
53 { "boost", &simgrid::kernel::context::boost_factory },
55 #if HAVE_THREAD_CONTEXTS
56 { "thread", &simgrid::kernel::context::thread_factory },
60 static_assert(sizeof(context_factories) != 0, "No context factories are enabled for this build");
62 // Create the list of possible contexts:
64 std::string contexts_list()
67 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
68 for (std::size_t i = 1; i != n; ++i) {
70 res += context_factories[i].first;
75 static simgrid::config::Flag<std::string> context_factory_name(
77 (std::string("Possible values: ")+contexts_list()).c_str(),
78 context_factories[0].first);
80 unsigned smx_context_stack_size;
81 int smx_context_stack_size_was_set = 0;
82 unsigned smx_context_guard_size;
83 int smx_context_guard_size_was_set = 0;
84 #if HAVE_THREAD_LOCAL_STORAGE
85 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
87 static xbt_os_thread_key_t smx_current_context_key = 0;
89 static smx_context_t smx_current_context_serial;
90 static int smx_parallel_contexts = 1;
91 static int smx_parallel_threshold = 2;
92 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
95 * This function is called by SIMIX_global_init() to initialize the context module.
97 void SIMIX_context_mod_init()
99 xbt_assert(simix_global->context_factory == nullptr);
101 #if HAVE_THREAD_CONTEXTS && not HAVE_THREAD_LOCAL_STORAGE
102 /* the __thread storage class is not available on this platform:
103 * use getspecific/setspecific instead to store the current context in each thread */
104 xbt_os_thread_key_create(&smx_current_context_key);
107 #if defined(__APPLE__) || defined(__NetBSD__)
108 if (context_factory_name == "thread" && xbt_cfg_get_string("smpi/privatization") == "dlopen") {
109 XBT_WARN("dlopen+thread broken on Apple and BSD. Switching to raw contexts.");
110 context_factory_name = "raw";
113 #if defined(__FreeBSD__)
114 if (context_factory_name == "thread" && xbt_cfg_get_string("smpi/privatization") != "no") {
115 XBT_WARN("mmap broken on FreeBSD, but dlopen+thread broken too. Switching to dlopen+raw contexts.");
116 context_factory_name = "raw";
120 /* select the context factory to use to create the contexts */
121 if (simgrid::kernel::context::factory_initializer) { // Give Java a chance to hijack the factory mechanism
122 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
125 /* use the factory specified by --cfg=contexts/factory:value */
126 for (auto const& factory : context_factories)
127 if (context_factory_name == factory.first) {
128 simix_global->context_factory = factory.second();
132 if (simix_global->context_factory == nullptr) {
133 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
134 #if HAVE_RAW_CONTEXTS
135 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
137 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
139 #if HAVE_UCONTEXT_CONTEXTS
140 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
142 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
144 #if HAVE_BOOST_CONTEXTS
145 XBT_ERROR(" boost: this uses the boost libraries context implementation");
147 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
149 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
150 xbt_die("Please use a valid factory.");
155 * This function is called by SIMIX_clean() to finalize the context module.
157 void SIMIX_context_mod_exit()
159 delete simix_global->context_factory;
160 simix_global->context_factory = nullptr;
163 void *SIMIX_context_stack_new()
167 /* FIXME: current code for stack overflow protection assumes that stacks are
168 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
169 * after the stack when PTH_STACKGROWTH == 1. */
171 if (smx_context_guard_size > 0 && not MC_is_active()) {
173 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
174 static int warned_once = 0;
175 if (not warned_once) {
176 XBT_WARN("Stack overflow protection is known to be broken on your system. Either stack grows upwards, or it was not even tested properly.");
181 size_t size = smx_context_stack_size + smx_context_guard_size;
183 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
184 * pointer returned by xbt_malloc0. */
185 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
186 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
187 *((void **)stack - 1) = alloc;
188 #elif !defined(_WIN32)
189 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
190 xbt_die("Failed to allocate stack.");
192 stack = _aligned_malloc(size, xbt_pagesize);
196 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
198 "Failed to protect stack: %s.\n"
199 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
200 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
201 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more info.",
203 /* This is fatal. We are going to fail at some point when we try reusing this. */
206 stack = (char *)stack + smx_context_guard_size;
208 stack = xbt_malloc0(smx_context_stack_size);
212 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
213 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
219 void SIMIX_context_stack_delete(void *stack)
225 unsigned int valgrind_stack_id;
226 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
227 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
231 if (smx_context_guard_size > 0 && not MC_is_active()) {
232 stack = (char *)stack - smx_context_guard_size;
233 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
234 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
235 /* try to pursue anyway */
238 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
239 stack = *((void **)stack - 1);
242 #endif /* not windows */
247 /** @brief Returns whether some parallel threads are used for the user contexts. */
248 int SIMIX_context_is_parallel() {
249 return smx_parallel_contexts > 1;
253 * @brief Returns the number of parallel threads used for the user contexts.
254 * \return the number of threads (1 means no parallelism)
256 int SIMIX_context_get_nthreads() {
257 return smx_parallel_contexts;
261 * \brief Sets the number of parallel threads to use
262 * for the user contexts.
264 * This function should be called before initializing SIMIX.
265 * A value of 1 means no parallelism (1 thread only).
266 * If the value is greater than 1, the thread support must be enabled.
268 * \param nb_threads the number of threads to use
270 void SIMIX_context_set_nthreads(int nb_threads) {
272 nb_threads = xbt_os_get_numcores();
273 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
275 #if !HAVE_THREAD_CONTEXTS
276 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
278 smx_parallel_contexts = nb_threads;
282 * \brief Returns the threshold above which user processes are run in parallel.
284 * If the number of threads is set to 1, there is no parallelism and this
285 * threshold has no effect.
287 * \return when the number of user processes ready to run is above
288 * this threshold, they are run in parallel
290 int SIMIX_context_get_parallel_threshold() {
291 return smx_parallel_threshold;
295 * \brief Sets the threshold above which user processes are run in parallel.
297 * If the number of threads is set to 1, there is no parallelism and this
298 * threshold has no effect.
300 * \param threshold when the number of user processes ready to run is above
301 * this threshold, they are run in parallel
303 void SIMIX_context_set_parallel_threshold(int threshold) {
304 smx_parallel_threshold = threshold;
308 * \brief Returns the synchronization mode used when processes are run in
310 * \return how threads are synchronized if processes are run in parallel
312 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode() {
313 return smx_parallel_synchronization_mode;
317 * \brief Sets the synchronization mode to use when processes are run in
319 * \param mode how to synchronize threads if processes are run in parallel
321 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
322 smx_parallel_synchronization_mode = mode;
326 * \brief Returns the current context of this thread.
327 * \return the current context of this thread
329 smx_context_t SIMIX_context_get_current()
331 if (SIMIX_context_is_parallel()) {
332 #if HAVE_THREAD_LOCAL_STORAGE
333 return smx_current_context_parallel;
335 return xbt_os_thread_get_specific(smx_current_context_key);
339 return smx_current_context_serial;
344 * \brief Sets the current context of this thread.
345 * \param context the context to set
347 void SIMIX_context_set_current(smx_context_t context)
349 if (SIMIX_context_is_parallel()) {
350 #if HAVE_THREAD_LOCAL_STORAGE
351 smx_current_context_parallel = context;
353 xbt_os_thread_set_specific(smx_current_context_key, context);
357 smx_current_context_serial = context;