1 /* a fast and simple context switching library */
3 /* Copyright (c) 2009-2015. The SimGrid Team.
4 * All rights reserved. */
6 /* This program is free software; you can redistribute it and/or modify it
7 * under the terms of the license (GNU LGPL) which comes with this package. */
12 #include <xbt/config.hpp>
13 #include <xbt/range.hpp>
15 #include "src/internal_config.h"
18 #include "xbt/xbt_os_thread.h"
19 #include "smx_private.h"
20 #include "smx_private.hpp"
21 #include "simgrid/sg_config.h"
22 #include "src/internal_config.h"
23 #include "simgrid/modelchecker.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::simix::ContextFactoryInitializer> context_factories[] = {
46 { "raw", simgrid::simix::raw_factory },
48 #if HAVE_UCONTEXT_CONTEXTS
49 { "ucontext", simgrid::simix::sysv_factory },
51 #if HAVE_BOOST_CONTEXTS
52 { "boost", simgrid::simix::boost_factory },
54 #if HAVE_THREAD_CONTEXTS
55 { "thread", simgrid::simix::thread_factory },
59 static_assert(sizeof(context_factories) != 0,
60 "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]);
69 for (std::size_t i = 1; i != n; ++i) {
71 res += context_factories[i].first;
76 static simgrid::config::Flag<std::string> context_factory_name(
78 (std::string("Possible values: ")+contexts_list()).c_str(),
79 context_factories[0].first);
81 int smx_context_stack_size;
82 int smx_context_stack_size_was_set = 0;
83 int smx_context_guard_size;
84 int smx_context_guard_size_was_set = 0;
85 #if HAVE_THREAD_LOCAL_STORAGE
86 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
88 static xbt_os_thread_key_t smx_current_context_key = 0;
90 static smx_context_t smx_current_context_serial;
91 static int smx_parallel_contexts = 1;
92 static int smx_parallel_threshold = 2;
93 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
96 void invalid_context_factory()
98 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
100 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
102 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
104 #if HAVE_UCONTEXT_CONTEXTS
105 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
107 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
109 #if HAVE_BOOST_CONTEXTS
110 XBT_ERROR(" boost: this uses the boost libraries context implementation");
112 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
114 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
115 xbt_die("Please use a valid factory.");
119 * This function is called by SIMIX_global_init() to initialize the context module.
121 void SIMIX_context_mod_init(void)
123 #if HAVE_THREAD_CONTEXTS && !HAVE_THREAD_LOCAL_STORAGE
124 /* the __thread storage class is not available on this platform:
125 * use getspecific/setspecific instead to store the current context in each thread */
126 xbt_os_thread_key_create(&smx_current_context_key);
128 if (simix_global->context_factory)
130 /* select the context factory to use to create the contexts */
131 if (simgrid::simix::factory_initializer) {
132 simix_global->context_factory = simgrid::simix::factory_initializer();
135 /* use the factory specified by --cfg=contexts/factory:value */
136 for (auto const& factory : context_factories)
137 if (context_factory_name == factory.first) {
138 simix_global->context_factory = factory.second();
141 if (simix_global->context_factory == nullptr)
142 invalid_context_factory();
146 * This function is called by SIMIX_clean() to finalize the context module.
148 void SIMIX_context_mod_exit(void)
150 delete simix_global->context_factory;
151 simix_global->context_factory = nullptr;
154 void *SIMIX_context_stack_new(void)
158 /* FIXME: current code for stack overflow protection assumes that stacks are
159 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
160 * after the stack when PTH_STACKGROWTH == 1. */
162 if (smx_context_guard_size > 0 && !MC_is_active()) {
164 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
165 static int warned_once = 0;
167 XBT_WARN("Stack overflow protection is known to be broken on your system. Either stack grows upwards, or it was not even tested properly.");
172 size_t size = smx_context_stack_size + smx_context_guard_size;
174 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
175 * pointer returned by xbt_malloc0. */
176 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
177 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
178 *((void **)stack - 1) = alloc;
179 #elif !defined(_WIN32)
180 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
181 xbt_die("Failed to allocate stack.");
183 stack = _aligned_malloc(size, xbt_pagesize);
187 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
188 xbt_die("Failed to protect stack: %s", strerror(errno));
189 /* This is fatal. We are going to fail at some point when
190 we tryi reusing this. */
193 stack = (char *)stack + smx_context_guard_size;
195 stack = xbt_malloc0(smx_context_stack_size);
199 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
200 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
206 void SIMIX_context_stack_delete(void *stack)
212 unsigned int valgrind_stack_id;
213 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
214 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
218 if (smx_context_guard_size > 0 && !MC_is_active()) {
219 stack = (char *)stack - smx_context_guard_size;
220 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
221 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
222 /* try to pursue anyway */
225 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
226 stack = *((void **)stack - 1);
229 #endif /* not windows */
234 /** @brief Returns whether some parallel threads are used for the user contexts. */
235 int SIMIX_context_is_parallel(void) {
236 return smx_parallel_contexts > 1;
240 * \brief Returns the number of parallel threads used
241 * for the user contexts.
242 * \return the number of threads (1 means no parallelism)
244 int SIMIX_context_get_nthreads(void) {
245 return smx_parallel_contexts;
249 * \brief Sets the number of parallel threads to use
250 * for the user contexts.
252 * This function should be called before initializing SIMIX.
253 * A value of 1 means no parallelism (1 thread only).
254 * If the value is greater than 1, the thread support must be enabled.
256 * \param nb_threads the number of threads to use
258 void SIMIX_context_set_nthreads(int nb_threads) {
260 nb_threads = xbt_os_get_numcores();
261 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
263 #if !HAVE_THREAD_CONTEXTS
264 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
266 smx_parallel_contexts = nb_threads;
270 * \brief Returns the threshold above which user processes are run in parallel.
272 * If the number of threads is set to 1, there is no parallelism and this
273 * threshold has no effect.
275 * \return when the number of user processes ready to run is above
276 * this threshold, they are run in parallel
278 int SIMIX_context_get_parallel_threshold(void) {
279 return smx_parallel_threshold;
283 * \brief Sets the threshold above which user processes are run in parallel.
285 * If the number of threads is set to 1, there is no parallelism and this
286 * threshold has no effect.
288 * \param threshold when the number of user processes ready to run is above
289 * this threshold, they are run in parallel
291 void SIMIX_context_set_parallel_threshold(int threshold) {
292 smx_parallel_threshold = threshold;
296 * \brief Returns the synchronization mode used when processes are run in
298 * \return how threads are synchronized if processes are run in parallel
300 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
301 return smx_parallel_synchronization_mode;
305 * \brief Sets the synchronization mode to use when processes are run in
307 * \param mode how to synchronize threads if processes are run in parallel
309 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
310 smx_parallel_synchronization_mode = mode;
314 * \brief Returns the current context of this thread.
315 * \return the current context of this thread
317 smx_context_t SIMIX_context_get_current(void)
319 if (SIMIX_context_is_parallel()) {
320 #if HAVE_THREAD_LOCAL_STORAGE
321 return smx_current_context_parallel;
323 return xbt_os_thread_get_specific(smx_current_context_key);
327 return smx_current_context_serial;
332 * \brief Sets the current context of this thread.
333 * \param context the context to set
335 void SIMIX_context_set_current(smx_context_t context)
337 if (SIMIX_context_is_parallel()) {
338 #if HAVE_THREAD_LOCAL_STORAGE
339 smx_current_context_parallel = context;
341 xbt_os_thread_set_specific(smx_current_context_key, context);
345 smx_current_context_serial = context;