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/portable.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
32 #ifdef HAVE_VALGRIND_VALGRIND_H
33 # include <valgrind/valgrind.h>
36 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(simix_context, simix,
37 "Context switching mechanism");
39 char* smx_context_factory_name = NULL; /* factory name specified by --cfg=contexts/factory:value */
40 int smx_context_stack_size;
41 int smx_context_stack_size_was_set = 0;
42 int smx_context_guard_size;
43 int smx_context_guard_size_was_set = 0;
44 #ifdef HAVE_THREAD_LOCAL_STORAGE
45 static XBT_THREAD_LOCAL smx_context_t smx_current_context_parallel;
47 static xbt_os_thread_key_t smx_current_context_key = 0;
49 static smx_context_t smx_current_context_serial;
50 static int smx_parallel_contexts = 1;
51 static int smx_parallel_threshold = 2;
52 static e_xbt_parmap_mode_t smx_parallel_synchronization_mode = XBT_PARMAP_DEFAULT;
55 * This function is called by SIMIX_global_init() to initialize the context module.
57 void SIMIX_context_mod_init(void)
59 #if defined(HAVE_THREAD_CONTEXTS) && !defined(HAVE_THREAD_LOCAL_STORAGE)
60 /* the __thread storage class is not available on this platform:
61 * use getspecific/setspecific instead to store the current context in each thread */
62 xbt_os_thread_key_create(&smx_current_context_key);
64 if (!simix_global->context_factory) {
65 /* select the context factory to use to create the contexts */
66 if (simgrid::simix::factory_initializer)
67 simix_global->context_factory = simgrid::simix::factory_initializer();
68 else { /* use the factory specified by --cfg=contexts/factory:value */
69 #if defined(HAVE_THREAD_CONTEXTS)
70 if (!strcmp(smx_context_factory_name, "thread"))
71 simix_global->context_factory = simgrid::simix::thread_factory();
75 #ifdef HAVE_UCONTEXT_CONTEXTS
76 else if (!strcmp(smx_context_factory_name, "ucontext"))
77 simix_global->context_factory = simgrid::simix::sysv_factory();
79 #ifdef HAVE_RAW_CONTEXTS
80 else if (!strcmp(smx_context_factory_name, "raw"))
81 simix_global->context_factory = simgrid::simix::raw_factory();
83 #ifdef HAVE_BOOST_CONTEXTS
84 else if (!strcmp(smx_context_factory_name, "boost"))
85 simix_global->context_factory = simgrid::simix::boost_factory();
88 XBT_ERROR("Invalid context factory specified. Valid factories on this machine:");
89 #ifdef HAVE_RAW_CONTEXTS
90 XBT_ERROR(" raw: high performance context factory implemented specifically for SimGrid");
92 XBT_ERROR(" (raw contexts were disabled at compilation time on this machine -- check configure logs for details)");
94 #ifdef HAVE_UCONTEXT_CONTEXTS
95 XBT_ERROR(" ucontext: classical system V contexts (implemented with makecontext, swapcontext and friends)");
97 XBT_ERROR(" (ucontext was disabled at compilation time on this machine -- check configure logs for details)");
99 #ifdef HAVE_BOOST_CONTEXTS
100 XBT_ERROR(" boost: this uses the boost libraries context implementation");
102 XBT_ERROR(" (boost was disabled at compilation time on this machine -- check configure logs for details. Did you install the libboost-context-dev package?)");
104 XBT_ERROR(" thread: slow portability layer using system threads (pthreads on UNIX, CreateThread() on windows)");
105 xbt_die("Please use a valid factory.");
112 * This function is called by SIMIX_clean() to finalize the context module.
114 void SIMIX_context_mod_exit(void)
116 delete simix_global->context_factory;
117 simix_global->context_factory = nullptr;
120 void *SIMIX_context_stack_new(void)
124 /* FIXME: current code for stack overflow protection assumes that stacks are
125 * growing downward (PTH_STACKGROWTH == -1). Protected pages need to be put
126 * after the stack when PTH_STACKGROWTH == 1. */
128 if (smx_context_guard_size > 0 && !MC_is_active()) {
130 #if defined(_WIN32) || (PTH_STACKGROWTH != -1)
131 static int warned_once = 0;
133 XBT_WARN("Stack overflow protection is known to be broken on your system. Either you're on Windows or PTH_STACKGROWTH != -1 (current value is %d).",
139 size_t size = smx_context_stack_size + smx_context_guard_size;
141 /* Cannot use posix_memalign when HAVE_MC. Align stack by hand, and save the
142 * pointer returned by xbt_malloc0. */
143 char *alloc = (char*)xbt_malloc0(size + xbt_pagesize);
144 stack = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
145 *((void **)stack - 1) = alloc;
146 #elif !defined(_WIN32)
147 if (posix_memalign(&stack, xbt_pagesize, size) != 0)
148 xbt_die("Failed to allocate stack.");
150 stack = _aligned_malloc(size, xbt_pagesize);
154 if (mprotect(stack, smx_context_guard_size, PROT_NONE) == -1) {
155 xbt_die("Failed to protect stack: %s", strerror(errno));
156 /* This is fatal. We are going to fail at some point when
157 we tryi reusing this. */
160 stack = (char *)stack + smx_context_guard_size;
162 stack = xbt_malloc0(smx_context_stack_size);
165 #ifdef HAVE_VALGRIND_VALGRIND_H
166 unsigned int valgrind_stack_id =
167 VALGRIND_STACK_REGISTER(stack, (char *)stack + smx_context_stack_size);
168 memcpy((char *)stack + smx_context_usable_stack_size, &valgrind_stack_id,
169 sizeof valgrind_stack_id);
175 void SIMIX_context_stack_delete(void *stack)
180 #ifdef HAVE_VALGRIND_VALGRIND_H
181 unsigned int valgrind_stack_id;
182 memcpy(&valgrind_stack_id, (char *)stack + smx_context_usable_stack_size,
183 sizeof valgrind_stack_id);
184 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
188 if (smx_context_guard_size > 0 && !MC_is_active()) {
189 stack = (char *)stack - smx_context_guard_size;
190 if (mprotect(stack, smx_context_guard_size,
191 PROT_READ | PROT_WRITE) == -1) {
192 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
193 /* try to pursue anyway */
196 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
197 stack = *((void **)stack - 1);
206 * \brief Returns whether some parallel threads are used
207 * for the user contexts.
208 * \return 1 if parallelism is used
210 int SIMIX_context_is_parallel(void) {
211 return smx_parallel_contexts > 1;
215 * \brief Returns the number of parallel threads used
216 * for the user contexts.
217 * \return the number of threads (1 means no parallelism)
219 int SIMIX_context_get_nthreads(void) {
220 return smx_parallel_contexts;
224 * \brief Sets the number of parallel threads to use
225 * for the user contexts.
227 * This function should be called before initializing SIMIX.
228 * A value of 1 means no parallelism (1 thread only).
229 * If the value is greater than 1, the thread support must be enabled.
231 * \param nb_threads the number of threads to use
233 void SIMIX_context_set_nthreads(int nb_threads) {
235 nb_threads = xbt_os_get_numcores();
236 XBT_INFO("Auto-setting contexts/nthreads to %d",nb_threads);
239 if (nb_threads > 1) {
240 #ifndef HAVE_THREAD_CONTEXTS
241 THROWF(arg_error, 0, "The thread factory cannot be run in parallel");
244 smx_parallel_contexts = nb_threads;
248 * \brief Returns 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 * \return when the number of user processes ready to run is above
254 * this threshold, they are run in parallel
256 int SIMIX_context_get_parallel_threshold(void) {
257 return smx_parallel_threshold;
261 * \brief Sets the threshold above which user processes are run in parallel.
263 * If the number of threads is set to 1, there is no parallelism and this
264 * threshold has no effect.
266 * \param threshold when the number of user processes ready to run is above
267 * this threshold, they are run in parallel
269 void SIMIX_context_set_parallel_threshold(int threshold) {
270 smx_parallel_threshold = threshold;
274 * \brief Returns the synchronization mode used when processes are run in
276 * \return how threads are synchronized if processes are run in parallel
278 e_xbt_parmap_mode_t SIMIX_context_get_parallel_mode(void) {
279 return smx_parallel_synchronization_mode;
283 * \brief Sets the synchronization mode to use when processes are run in
285 * \param mode how to synchronize threads if processes are run in parallel
287 void SIMIX_context_set_parallel_mode(e_xbt_parmap_mode_t mode) {
288 smx_parallel_synchronization_mode = mode;
292 * \brief Returns the current context of this thread.
293 * \return the current context of this thread
295 smx_context_t SIMIX_context_get_current(void)
297 if (SIMIX_context_is_parallel()) {
298 #ifdef HAVE_THREAD_LOCAL_STORAGE
299 return smx_current_context_parallel;
301 return xbt_os_thread_get_specific(smx_current_context_key);
305 return smx_current_context_serial;
310 * \brief Sets the current context of this thread.
311 * \param context the context to set
313 void SIMIX_context_set_current(smx_context_t context)
315 if (SIMIX_context_is_parallel()) {
316 #ifdef HAVE_THREAD_LOCAL_STORAGE
317 smx_current_context_parallel = context;
319 xbt_os_thread_set_specific(smx_current_context_key, context);
323 smx_current_context_serial = context;