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. */
9 #include "src/internal_config.h"
12 #include "xbt/xbt_os_thread.h"
13 #include "smx_private.h"
14 #include "smx_private.hpp"
15 #include "simgrid/sg_config.h"
16 #include "src/internal_config.h"
17 #include "simgrid/modelchecker.h"
28 #define _aligned_malloc __mingw_aligned_malloc
29 #define _aligned_free __mingw_aligned_free
33 # include <valgrind/valgrind.h>
36 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix, "Context switching mechanism");
38 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
39 int smx_context_stack_size;
40 int smx_context_stack_size_was_set = 0;
41 int smx_context_guard_size;
42 int smx_context_guard_size_was_set = 0;
43 #if HAVE_THREAD_LOCAL_STORAGE
44 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
46 static xbt_os_thread_key_t smx_current_context_key = 0;
48 static smx_context_t smx_current_context_serial;
49 static int smx_parallel_contexts = 1;
50 static int smx_parallel_threshold = 2;
51 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
54 * This function is called by SIMIX_global_init() to initialize the context module.
56 void SIMIX_context_mod_init(void)
58 #if HAVE_THREAD_CONTEXTS && !HAVE_THREAD_LOCAL_STORAGE
59 /* the __thread storage class is not available on this platform:
60 * use getspecific/setspecific instead to store the current context in each thread */
61 xbt_os_thread_key_create(&smx_current_context_key);
63 if (!simix_global->context_factory) {
64 /* select the context factory to use to create the contexts */
65 if (simgrid::simix::factory_initializer)
66 simix_global->context_factory = simgrid::simix::factory_initializer();
67 else { /* use the factory specified by --cfg=contexts/factory:value */
68 #if HAVE_THREAD_CONTEXTS
69 if (!strcmp(smx_context_factory_name, "thread"))
70 simix_global->context_factory = simgrid::simix::thread_factory();
74 #if HAVE_UCONTEXT_CONTEXTS
75 else if (!strcmp(smx_context_factory_name, "ucontext"))
76 simix_global->context_factory = simgrid::simix::sysv_factory();
79 else if (!strcmp(smx_context_factory_name, "raw"))
80 simix_global->context_factory = simgrid::simix::raw_factory();
82 #if HAVE_BOOST_CONTEXTS
83 else if (!strcmp(smx_context_factory_name, "boost"))
84 simix_global->context_factory = simgrid::simix::boost_factory();
87 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
89 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
91 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
93 #if HAVE_UCONTEXT_CONTEXTS
94 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
96 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
98 #if HAVE_BOOST_CONTEXTS
99 XBT_ERROR(" boost: this uses the boost libraries context implementation");
101 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
103 XBT_ERROR(" thread: slow portability layer using pthreads as provided by gcc");
104 xbt_die("Please use a valid factory.");
111 * This function is called by SIMIX_clean() to finalize the context module.
113 void SIMIX_context_mod_exit(void)
115 delete simix_global->context_factory;
116 simix_global->context_factory = nullptr;
119 void *SIMIX_context_stack_new(void)
123 /* FIXME: current code for stack overflow protection assumes that stacks are
124 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
125 * after the stack when PTH_STACKGROWTH == 1. */
127 if (smx_context_guard_size > 0 && !MC_is_active()) {
129 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
130 static int warned_once = 0;
132 XBT_WARN("Stack overflow protection is known to be broken on your system. Either stack grows upwards, or it was not even tested properly.");
137 size_t size = smx_context_stack_size + smx_context_guard_size;
139 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
140 * pointer returned by xbt_malloc0. */
141 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
142 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
143 *((void **)stack - 1) = alloc;
144 #elif !defined(_WIN32)
145 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
146 xbt_die("Failed to allocate stack.");
148 stack = _aligned_malloc(size, xbt_pagesize);
152 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
153 xbt_die("Failed to protect stack: %s", strerror(errno));
154 /* This is fatal. We are going to fail at some point when
155 we tryi reusing this. */
158 stack = (char *)stack + smx_context_guard_size;
160 stack = xbt_malloc0(smx_context_stack_size);
164 unsigned int valgrind_stack_id = VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
165 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
171 void SIMIX_context_stack_delete(void *stack)
177 unsigned int valgrind_stack_id;
178 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size, sizeof valgrind_stack_id);
179 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
183 if (smx_context_guard_size > 0 && !MC_is_active()) {
184 stack = (char *)stack - smx_context_guard_size;
185 if (mprotect(stack, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
186 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
187 /* try to pursue anyway */
190 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
191 stack = *((void **)stack - 1);
194 #endif /* not windows */
199 /** @brief Returns whether some parallel threads are used for the user contexts. */
200 int SIMIX_context_is_parallel(void) {
201 return smx_parallel_contexts > 1;
205 * \brief Returns the number of parallel threads used
206 * for the user contexts.
207 * \return the number of threads (1 means no parallelism)
209 int SIMIX_context_get_nthreads(void) {
210 return smx_parallel_contexts;
214 * \brief Sets the number of parallel threads to use
215 * for the user contexts.
217 * This function should be called before initializing SIMIX.
218 * A value of 1 means no parallelism (1 thread only).
219 * If the value is greater than 1, the thread support must be enabled.
221 * \param nb_threads the number of threads to use
223 void SIMIX_context_set_nthreads(int nb_threads) {
225 nb_threads = xbt_os_get_numcores();
226 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
228 #if !HAVE_THREAD_CONTEXTS
229 xbt_assert(nb_threads == 1, "Parallel runs are impossible when the pthreads are missing.");
231 smx_parallel_contexts = nb_threads;
235 * \brief Returns the threshold above which user processes are run in parallel.
237 * If the number of threads is set to 1, there is no parallelism and this
238 * threshold has no effect.
240 * \return when the number of user processes ready to run is above
241 * this threshold, they are run in parallel
243 int SIMIX_context_get_parallel_threshold(void) {
244 return smx_parallel_threshold;
248 * \brief Sets the threshold above which user processes are run in parallel.
250 * If the number of threads is set to 1, there is no parallelism and this
251 * threshold has no effect.
253 * \param threshold when the number of user processes ready to run is above
254 * this threshold, they are run in parallel
256 void SIMIX_context_set_parallel_threshold(int threshold) {
257 smx_parallel_threshold = threshold;
261 * \brief Returns the synchronization mode used when processes are run in
263 * \return how threads are synchronized if processes are run in parallel
265 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
266 return smx_parallel_synchronization_mode;
270 * \brief Sets the synchronization mode to use when processes are run in
272 * \param mode how to synchronize threads if processes are run in parallel
274 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
275 smx_parallel_synchronization_mode = mode;
279 * \brief Returns the current context of this thread.
280 * \return the current context of this thread
282 smx_context_t SIMIX_context_get_current(void)
284 if (SIMIX_context_is_parallel()) {
285 #if HAVE_THREAD_LOCAL_STORAGE
286 return smx_current_context_parallel;
288 return xbt_os_thread_get_specific(smx_current_context_key);
292 return smx_current_context_serial;
297 * \brief Sets the current context of this thread.
298 * \param context the context to set
300 void SIMIX_context_set_current(smx_context_t context)
302 if (SIMIX_context_is_parallel()) {
303 #if HAVE_THREAD_LOCAL_STORAGE
304 smx_current_context_parallel = context;
306 xbt_os_thread_set_specific(smx_current_context_key, context);
310 smx_current_context_serial = context;