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 "src/internal_config.h"
22 #include "xbt/xbt_os_thread.h"
23 #include "smx_private.h"
24 #include "simgrid/sg_config.h"
25 #include "src/internal_config.h"
26 #include "simgrid/modelchecker.h"
37 #define _aligned_malloc __mingw_aligned_malloc
38 #define _aligned_free __mingw_aligned_free
42 # include <valgrind/valgrind.h>
45 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
47 static std::pair<const char*, simgrid::kernel::context::ContextFactoryInitializer> context_factories[] = {
49 { "raw", &simgrid::kernel::context::raw_factory },
51 #if HAVE_UCONTEXT_CONTEXTS
52 { "ucontext", &simgrid::kernel::context::sysv_factory },
54 #if HAVE_BOOST_CONTEXTS
55 { "boost", &simgrid::kernel::context::boost_factory },
57 #if HAVE_THREAD_CONTEXTS
58 { "thread", &simgrid::kernel::context::thread_factory },
62 static_assert(sizeof(context_factories) != 0, "No context factories are enabled for this build");
64 // Create the list of possible contexts:
66 std::string contexts_list()
69 const std::size_t n = sizeof(context_factories) / sizeof(context_factories[0]);
70 for (std::size_t i = 1; i != n; ++i) {
72 res += context_factories[i].first;
77 static simgrid::config::Flag<std::string> context_factory_name(
79 (std::string("Possible values: ")+contexts_list()).c_str(),
80 context_factories[0].first);
82 int smx_context_stack_size;
83 int smx_context_stack_size_was_set = 0;
84 int smx_context_guard_size;
85 int smx_context_guard_size_was_set = 0;
86 #if HAVE_THREAD_LOCAL_STORAGE
87 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
89 static xbt_os_thread_key_t smx_current_context_key = 0;
91 static smx_context_t smx_current_context_serial;
92 static int smx_parallel_contexts = 1;
93 static int smx_parallel_threshold = 2;
94 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
97 * This function is called by SIMIX_global_init() to initialize the context module.
99 void SIMIX_context_mod_init()
101 xbt_assert(simix_global->context_factory == nullptr);
103 #if HAVE_THREAD_CONTEXTS && !HAVE_THREAD_LOCAL_STORAGE
104 /* the __thread storage class is not available on this platform:
105 * use getspecific/setspecific instead to store the current context in each thread */
106 xbt_os_thread_key_create(&smx_current_context_key);
109 /* select the context factory to use to create the contexts */
110 if (simgrid::kernel::context::factory_initializer) { // Give Java a chance to hijack the factory mechanism
111 simix_global->context_factory = simgrid::kernel::context::factory_initializer();
114 /* use the factory specified by --cfg=contexts/factory:value */
115 for (auto const& factory : context_factories)
116 if (context_factory_name == factory.first) {
117 simix_global->context_factory = factory.second();
121 if (simix_global->context_factory == nullptr) {
122 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
123 #if HAVE_RAW_CONTEXTS
124 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
126 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
128 #if HAVE_UCONTEXT_CONTEXTS
129 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
131 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
133 #if HAVE_BOOST_CONTEXTS
134 XBT_ERROR(" boost: this uses the boost libraries context implementation");
136 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
138 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
139 xbt_die("Please use a valid factory.");
144 * This function is called by SIMIX_clean() to finalize the context module.
146 void SIMIX_context_mod_exit()
148 delete simix_global->context_factory;
149 simix_global->context_factory = nullptr;
152 void *SIMIX_context_stack_new()
156 /* FIXME: current code for stack overflow protection assumes that stacks are
157 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
158 * after the stack when PTH_STACKGROWTH == 1. */
160 if (smx_context_guard_size > 0 && !MC_is_active()) {
162 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
163 static int warned_once = 0;
165 XBT_WARN("Stack overflow protection is known to be broken on your system. Either stack grows upwards, or it was not even tested properly.");
170 size_t size = smx_context_stack_size + smx_context_guard_size;
172 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
173 * pointer returned by xbt_malloc0. */
174 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
175 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
176 *((void **)stack - 1) = alloc;
177 #elif !defined(_WIN32)
178 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
179 xbt_die("Failed to allocate stack.");
181 stack = _aligned_malloc(size, xbt_pagesize);
185 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
187 "Failed to protect stack: %s.\n"
188 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
189 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
190 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more info.",
192 /* This is fatal. We are going to fail at some point when we try reusing this. */
195 stack = (char *)stack + smx_context_guard_size;
197 stack = xbt_malloc0(smx_context_stack_size);
201 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
202 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
208 void SIMIX_context_stack_delete(void *stack)
214 unsigned int valgrind_stack_id;
215 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
216 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
220 if (smx_context_guard_size > 0 && !MC_is_active()) {
221 stack = (char *)stack - smx_context_guard_size;
222 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
223 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
224 /* try to pursue anyway */
227 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
228 stack = *((void **)stack - 1);
231 #endif /* not windows */
236 /** @brief Returns whether some parallel threads are used for the user contexts. */
237 int SIMIX_context_is_parallel() {
238 return smx_parallel_contexts > 1;
242 * @brief Returns the number of parallel threads used for the user contexts.
243 * \return the number of threads (1 means no parallelism)
245 int SIMIX_context_get_nthreads() {
246 return smx_parallel_contexts;
250 * \brief Sets the number of parallel threads to use
251 * for the user contexts.
253 * This function should be called before initializing SIMIX.
254 * A value of 1 means no parallelism (1 thread only).
255 * If the value is greater than 1, the thread support must be enabled.
257 * \param nb_threads the number of threads to use
259 void SIMIX_context_set_nthreads(int nb_threads) {
261 nb_threads = xbt_os_get_numcores();
262 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
264 #if !HAVE_THREAD_CONTEXTS
265 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
267 smx_parallel_contexts = nb_threads;
271 * \brief Returns the threshold above which user processes are run in parallel.
273 * If the number of threads is set to 1, there is no parallelism and this
274 * threshold has no effect.
276 * \return when the number of user processes ready to run is above
277 * this threshold, they are run in parallel
279 int SIMIX_context_get_parallel_threshold() {
280 return smx_parallel_threshold;
284 * \brief Sets the threshold above which user processes are run in parallel.
286 * If the number of threads is set to 1, there is no parallelism and this
287 * threshold has no effect.
289 * \param threshold when the number of user processes ready to run is above
290 * this threshold, they are run in parallel
292 void SIMIX_context_set_parallel_threshold(int threshold) {
293 smx_parallel_threshold = threshold;
297 * \brief Returns the synchronization mode used when processes are run in
299 * \return how threads are synchronized if processes are run in parallel
301 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode() {
302 return smx_parallel_synchronization_mode;
306 * \brief Sets the synchronization mode to use when processes are run in
308 * \param mode how to synchronize threads if processes are run in parallel
310 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
311 smx_parallel_synchronization_mode = mode;
315 * \brief Returns the current context of this thread.
316 * \return the current context of this thread
318 smx_context_t SIMIX_context_get_current()
320 if (SIMIX_context_is_parallel()) {
321 #if HAVE_THREAD_LOCAL_STORAGE
322 return smx_current_context_parallel;
324 return xbt_os_thread_get_specific(smx_current_context_key);
328 return smx_current_context_serial;
333 * \brief Sets the current context of this thread.
334 * \param context the context to set
336 void SIMIX_context_set_current(smx_context_t context)
338 if (SIMIX_context_is_parallel()) {
339 #if HAVE_THREAD_LOCAL_STORAGE
340 smx_current_context_parallel = context;
342 xbt_os_thread_set_specific(smx_current_context_key, context);
346 smx_current_context_serial = context;