1 /* Copyright (c) 2009-2019. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "simgrid/modelchecker.h"
7 #include "src/internal_config.h"
8 #include "src/kernel/context/context_private.hpp"
9 #include "src/simix/ActorImpl.hpp"
10 #include "src/simix/smx_private.hpp"
11 #include "xbt/parmap.hpp"
13 #include "src/kernel/context/ContextSwapped.hpp"
23 #define _aligned_malloc __mingw_aligned_malloc
24 #define _aligned_free __mingw_aligned_free
28 #include <valgrind/valgrind.h>
31 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
37 /* rank of the execution thread */
38 thread_local uintptr_t SwappedContext::worker_id_; /* thread-specific storage for the thread id */
40 SwappedContextFactory::SwappedContextFactory() : ContextFactory(), parallel_(SIMIX_context_is_parallel())
42 parmap_ = nullptr; // will be created lazily with the right parameters if needed (ie, in parallel)
43 workers_context_.resize(parallel_ ? SIMIX_context_get_nthreads() : 1, nullptr);
45 SwappedContextFactory::~SwappedContextFactory()
50 SwappedContext::SwappedContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process,
51 SwappedContextFactory* factory)
52 : Context(std::move(code), cleanup_func, process), factory_(factory)
54 // Save maestro (=context created first) in preparation for run_all
55 if (not factory->parallel_ && factory_->workers_context_[0] == nullptr)
56 factory_->workers_context_[0] = this;
59 if (smx_context_guard_size > 0 && not MC_is_active()) {
61 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
63 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
65 "Please disable stack guards with --cfg=contexts:guard-size:0");
66 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
67 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
70 size_t size = smx_context_stack_size + smx_context_guard_size;
72 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
73 * pointer returned by xbt_malloc0. */
74 char* alloc = (char*)xbt_malloc0(size + xbt_pagesize);
75 stack_ = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
76 *((void**)stack_ - 1) = alloc;
77 #elif !defined(_WIN32)
78 if (posix_memalign(&this->stack_, xbt_pagesize, size) != 0)
79 xbt_die("Failed to allocate stack.");
81 this->stack_ = _aligned_malloc(size, xbt_pagesize);
85 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
87 "Failed to protect stack: %s.\n"
88 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
89 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
90 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more "
93 /* This is fatal. We are going to fail at some point when we try reusing this. */
96 this->stack_ = (char*)this->stack_ + smx_context_guard_size;
98 this->stack_ = xbt_malloc0(smx_context_stack_size);
101 #if PTH_STACKGROWTH == -1
102 ASAN_ONLY(this->asan_stack_ = static_cast<char*>(this->stack_) + smx_context_usable_stack_size);
104 ASAN_ONLY(this->asan_stack_ = this->stack_);
107 unsigned int valgrind_stack_id =
108 VALGRIND_STACK_REGISTER(this->stack_, (char*)this->stack_ + smx_context_stack_size);
109 memcpy((char*)this->stack_ + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
114 SwappedContext::~SwappedContext()
116 if (stack_ == nullptr) // maestro has no extra stack
120 unsigned int valgrind_stack_id;
121 memcpy(&valgrind_stack_id, (char*)stack_ + smx_context_usable_stack_size, sizeof valgrind_stack_id);
122 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
126 if (smx_context_guard_size > 0 && not MC_is_active()) {
127 stack_ = (char*)stack_ - smx_context_guard_size;
128 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
129 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
130 /* try to pursue anyway */
133 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
134 stack_ = *((void**)stack_ - 1);
137 #endif /* not windows */
142 void* SwappedContext::get_stack()
147 void SwappedContext::stop()
150 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
154 /** Maestro wants to run all ready actors */
155 void SwappedContextFactory::run_all()
157 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
158 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
159 * for the ones of the simulated processes that must run.
162 threads_working_ = 0;
164 // We lazily create the parmap so that all options are actually processed when doing so.
165 if (parmap_ == nullptr)
166 parmap_ = new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
168 // Usually, Parmap::apply() executes the provided function on all elements of the array.
169 // Here, the executed function does not return the control to the parmap before all the array is processed:
170 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
171 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
172 // It only yields back to worker_context when the work array is exhausted.
173 // - So, resume() is only launched from the parmap for the first job of each minion.
175 [](smx_actor_t process) {
176 SwappedContext* context = static_cast<SwappedContext*>(process->context_);
179 simix_global->process_to_run);
180 } else { // sequential execution
181 if (simix_global->process_to_run.empty())
184 /* maestro is already saved in the first slot of workers_context_ */
185 smx_actor_t first_actor = simix_global->process_to_run.front();
187 /* execute the first actor; it will chain to the others when using suspend() */
188 static_cast<SwappedContext*>(first_actor->context_)->resume();
192 /** Maestro wants to yield back to a given actor, so awake it on the current thread
194 * In parallel, it is only applied to the N first elements of the parmap array,
195 * where N is the amount of worker threads in the parmap.
196 * See SwappedContextFactory::run_all for details.
198 void SwappedContext::resume()
200 if (factory_->parallel_) {
201 // Save the thread number (my body) in an os-thread-specific area
202 worker_id_ = factory_->threads_working_.fetch_add(1, std::memory_order_relaxed);
203 // Save my current soul (either maestro, or one of the minions) in a permanent area
204 SwappedContext* worker_context = static_cast<SwappedContext*>(self());
205 factory_->workers_context_[worker_id_] = worker_context;
206 // Switch my soul and the actor's one
207 Context::set_current(this);
208 worker_context->swap_into(this);
209 // No body runs that soul anymore at this point, but it is stored in a safe place.
210 // When the executed actor will do a blocking action, SIMIX_process_yield() will call suspend(), below.
211 } else { // sequential execution
212 SwappedContext* old = static_cast<SwappedContext*>(self());
213 Context::set_current(this);
214 old->swap_into(this);
218 /** The actor wants to yield back to maestro, because it is blocked in a simcall (ie in SIMIX_process_yield())
220 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
222 * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
223 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
224 * and directly forth to the next executable actor.
226 void SwappedContext::suspend()
228 if (factory_->parallel_) {
229 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
230 boost::optional<smx_actor_t> next_work = factory_->parmap_->next();
231 SwappedContext* next_context;
233 // There is a next soul to embody (ie, another executable actor)
234 XBT_DEBUG("Run next process");
235 next_context = static_cast<SwappedContext*>(next_work.get()->context_);
237 // All actors were run, go back to the parmap context
238 XBT_DEBUG("No more actors to run");
239 // worker_id_ is the identity of my body, stored in thread_local when starting the scheduling round
240 next_context = factory_->workers_context_[worker_id_];
241 // When given that soul, the body will wait for the next scheduling round
244 // Get the next soul to run, either from another actor or the initial minion's one
245 Context::set_current(next_context);
246 this->swap_into(next_context);
248 } else { // sequential execution
249 /* determine the next context */
250 SwappedContext* next_context;
251 unsigned long int i = factory_->process_index_;
252 factory_->process_index_++;
254 if (i < simix_global->process_to_run.size()) {
255 /* Actually swap into the next actor directly without transiting to maestro */
256 XBT_DEBUG("Run next actor");
257 next_context = static_cast<SwappedContext*>(simix_global->process_to_run[i]->context_);
259 /* all processes were run, actually return to maestro */
260 XBT_DEBUG("No more actors to run");
261 next_context = factory_->workers_context_[0];
263 Context::set_current(next_context);
264 this->swap_into(next_context);
268 } // namespace context
269 } // namespace kernel
270 } // namespace simgrid