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(std::string name)
41 : ContextFactory(name), parallel_(SIMIX_context_is_parallel())
43 parmap_ = nullptr; // will be created lazily with the right parameters if needed (ie, in parallel)
44 workers_context_.clear();
45 workers_context_.resize(parallel_ ? SIMIX_context_get_nthreads() : 1, nullptr);
47 SwappedContextFactory::~SwappedContextFactory()
51 workers_context_.clear();
54 SwappedContext::SwappedContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process,
55 SwappedContextFactory* factory)
56 : Context(std::move(code), cleanup_func, process), factory_(factory)
58 // Save maestro (=context created first) in preparation for run_all
59 if (factory_->workers_context_[0] == nullptr)
60 factory_->workers_context_[0] = this;
63 if (smx_context_guard_size > 0 && not MC_is_active()) {
65 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
67 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
69 "Please disable stack guards with --cfg=contexts:guard-size:0");
70 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
71 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
74 size_t size = smx_context_stack_size + smx_context_guard_size;
76 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
77 * pointer returned by xbt_malloc0. */
78 char* alloc = (char*)xbt_malloc0(size + xbt_pagesize);
79 stack_ = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
80 *((void**)stack_ - 1) = alloc;
81 #elif !defined(_WIN32)
82 if (posix_memalign(&this->stack_, xbt_pagesize, size) != 0)
83 xbt_die("Failed to allocate stack.");
85 this->stack_ = _aligned_malloc(size, xbt_pagesize);
89 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
91 "Failed to protect stack: %s.\n"
92 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
93 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
94 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more "
97 /* This is fatal. We are going to fail at some point when we try reusing this. */
100 this->stack_ = (char*)this->stack_ + smx_context_guard_size;
102 this->stack_ = xbt_malloc0(smx_context_stack_size);
106 unsigned int valgrind_stack_id =
107 VALGRIND_STACK_REGISTER(this->stack_, (char*)this->stack_ + smx_context_stack_size);
108 memcpy((char*)this->stack_ + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
113 SwappedContext::~SwappedContext()
115 if (stack_ == nullptr) // maestro has no extra stack
119 unsigned int valgrind_stack_id;
120 memcpy(&valgrind_stack_id, (char*)stack_ + smx_context_usable_stack_size, sizeof valgrind_stack_id);
121 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
125 if (smx_context_guard_size > 0 && not MC_is_active()) {
126 stack_ = (char*)stack_ - smx_context_guard_size;
127 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
128 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
129 /* try to pursue anyway */
132 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
133 stack_ = *((void**)stack_ - 1);
136 #endif /* not windows */
141 void* SwappedContext::get_stack()
146 void SwappedContext::stop()
149 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
153 /** Maestro wants to run all ready actors */
154 void SwappedContextFactory::run_all()
156 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
157 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
158 * for the ones of the simulated processes that must run.
161 threads_working_ = 0;
163 // We lazily create the parmap so that all options are actually processed when doing so.
164 if (parmap_ == nullptr)
165 parmap_ = new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
167 // Usually, Parmap::apply() executes the provided function on all elements of the array.
168 // Here, the executed function does not return the control to the parmap before all the array is processed:
169 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
170 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
171 // It only yields back to worker_context when the work array is exhausted.
172 // - So, resume() is only launched from the parmap for the first job of each minion.
174 [](smx_actor_t process) {
175 SwappedContext* context = static_cast<SwappedContext*>(process->context_);
178 simix_global->process_to_run);
179 } else { // sequential execution
180 if (simix_global->process_to_run.empty())
183 /* maestro is already saved in the first slot of workers_context_ */
184 smx_actor_t first_actor = simix_global->process_to_run.front();
186 /* execute the first actor; it will chain to the others when using suspend() */
187 static_cast<SwappedContext*>(first_actor->context_)->resume();
191 /** Maestro wants to yield back to a given actor, so awake it on the current thread
193 * In parallel, it is only applied to the N first elements of the parmap array,
194 * where N is the amount of worker threads in the parmap.
195 * See SwappedContextFactory::run_all for details.
197 void SwappedContext::resume()
199 if (factory_->parallel_) {
200 // Save the thread number (my body) in an os-thread-specific area
201 worker_id_ = factory_->threads_working_.fetch_add(1, std::memory_order_relaxed);
202 // Save my current soul (either maestro, or one of the minions) in a permanent area
203 SwappedContext* worker_context = static_cast<SwappedContext*>(self());
204 factory_->workers_context_[worker_id_] = worker_context;
205 // Switch my soul and the actor's one
206 Context::set_current(this);
207 worker_context->swap_into(this);
208 // No body runs that soul anymore at this point, but it is stored in a safe place.
209 // When the executed actor will do a blocking action, SIMIX_process_yield() will call suspend(), below.
210 } else { // sequential execution
211 SwappedContext* old = static_cast<SwappedContext*>(self());
212 Context::set_current(this);
213 old->swap_into(this);
217 /** The actor wants to yield back to maestro, because it is blocked in a simcall (ie in SIMIX_process_yield())
219 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
221 * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
222 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
223 * and directly forth to the next executable actor.
225 void SwappedContext::suspend()
227 if (factory_->parallel_) {
228 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
229 boost::optional<smx_actor_t> next_work = factory_->parmap_->next();
230 SwappedContext* next_context;
232 // There is a next soul to embody (ie, another executable actor)
233 XBT_DEBUG("Run next process");
234 next_context = static_cast<SwappedContext*>(next_work.get()->context_);
236 // All actors were run, go back to the parmap context
237 XBT_DEBUG("No more actors to run");
238 // worker_id_ is the identity of my body, stored in thread_local when starting the scheduling round
239 next_context = factory_->workers_context_[worker_id_];
240 // When given that soul, the body will wait for the next scheduling round
243 // Get the next soul to run, either from another actor or the initial minion's one
244 Context::set_current(next_context);
245 this->swap_into(next_context);
247 } else { // sequential execution
248 /* determine the next context */
249 SwappedContext* next_context;
250 unsigned long int i = factory_->process_index_;
251 factory_->process_index_++;
253 if (i < simix_global->process_to_run.size()) {
254 /* Actually swap into the next actor directly without transiting to maestro */
255 XBT_DEBUG("Run next actor");
256 next_context = static_cast<SwappedContext*>(simix_global->process_to_run[i]->context_);
258 /* all processes were run, actually return to maestro */
259 XBT_DEBUG("No more actors to run");
260 next_context = factory_->workers_context_[0];
262 Context::set_current(next_context);
263 this->swap_into(next_context);
267 } // namespace context
268 } // namespace kernel
269 } // namespace simgrid