1 /* Copyright (c) 2009-2018. 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"
14 #include "src/kernel/context/ContextUnix.hpp" // FIXME: temporary reverse import
24 #define _aligned_malloc __mingw_aligned_malloc
25 #define _aligned_free __mingw_aligned_free
29 #include <valgrind/valgrind.h>
32 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
38 /* Parallel execution */
39 simgrid::xbt::Parmap<smx_actor_t>* SwappedContext::parmap_;
40 std::atomic<uintptr_t> SwappedContext::threads_working_; /* number of threads that have started their work */
41 thread_local uintptr_t SwappedContext::worker_id_; /* thread-specific storage for the thread id */
42 std::vector<SwappedContext*> SwappedContext::workers_context_; /* space to save the worker's context in each thread */
44 SwappedContextFactory::SwappedContextFactory(std::string name)
45 : ContextFactory(name), parallel_(SIMIX_context_is_parallel())
47 SwappedContext::set_maestro(nullptr);
48 SwappedContext::initialize(parallel_);
50 SwappedContextFactory::~SwappedContextFactory()
52 SwappedContext::finalize();
55 void SwappedContext::initialize(bool parallel)
57 parmap_ = nullptr; // will be created lazily with the right parameters if needed (ie, in parallel)
59 workers_context_.clear();
60 workers_context_.resize(SIMIX_context_get_nthreads(), nullptr);
64 void SwappedContext::finalize()
68 workers_context_.clear();
71 SwappedContext* SwappedContext::maestro_context_ = nullptr;
73 SwappedContext::SwappedContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process,
74 SwappedContextFactory* factory)
75 : Context(std::move(code), cleanup_func, process), factory_(factory)
78 if (smx_context_guard_size > 0 && not MC_is_active()) {
80 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
82 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
84 "Please disable stack guards with --cfg=contexts:guard-size:0");
85 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
86 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
89 size_t size = smx_context_stack_size + smx_context_guard_size;
91 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
92 * pointer returned by xbt_malloc0. */
93 char* alloc = (char*)xbt_malloc0(size + xbt_pagesize);
94 stack_ = alloc - ((uintptr_t)alloc & (xbt_pagesize - 1)) + xbt_pagesize;
95 *((void**)stack_ - 1) = alloc;
96 #elif !defined(_WIN32)
97 if (posix_memalign(&this->stack_, xbt_pagesize, size) != 0)
98 xbt_die("Failed to allocate stack.");
100 this->stack_ = _aligned_malloc(size, xbt_pagesize);
104 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
106 "Failed to protect stack: %s.\n"
107 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
108 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
109 "Please see http://simgrid.gforge.inria.fr/simgrid/latest/doc/html/options.html#options_virt for more "
112 /* This is fatal. We are going to fail at some point when we try reusing this. */
115 this->stack_ = (char*)this->stack_ + smx_context_guard_size;
117 this->stack_ = xbt_malloc0(smx_context_stack_size);
121 unsigned int valgrind_stack_id =
122 VALGRIND_STACK_REGISTER(this->stack_, (char*)this->stack_ + smx_context_stack_size);
123 memcpy((char*)this->stack_ + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
128 SwappedContext::~SwappedContext()
130 if (stack_ == nullptr) // maestro has no extra stack
134 unsigned int valgrind_stack_id;
135 memcpy(&valgrind_stack_id, (char*)stack_ + smx_context_usable_stack_size, sizeof valgrind_stack_id);
136 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
140 if (smx_context_guard_size > 0 && not MC_is_active()) {
141 stack_ = (char*)stack_ - smx_context_guard_size;
142 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
143 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
144 /* try to pursue anyway */
147 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
148 stack_ = *((void**)stack_ - 1);
151 #endif /* not windows */
156 void SwappedContext::stop()
162 /** Maestro wants to run all ready actors */
163 void SwappedContextFactory::run_all()
165 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
166 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
167 * for the ones of the simulated processes that must run.
170 SwappedContext::threads_working_ = 0;
172 // We lazily create the parmap so that all options are actually processed when doing so.
173 if (SwappedContext::parmap_ == nullptr)
174 SwappedContext::parmap_ =
175 new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
177 // Usually, Parmap::apply() executes the provided function on all elements of the array.
178 // Here, the executed function does not return the control to the parmap before all the array is processed:
179 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
180 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
181 // It only yields back to worker_context when the work array is exhausted.
182 // - So, resume() is only launched from the parmap for the first job of each minion.
183 SwappedContext::parmap_->apply(
184 [](smx_actor_t process) {
185 SwappedContext* context = static_cast<SwappedContext*>(process->context_);
188 simix_global->process_to_run);
189 } else { // sequential execution
190 if (simix_global->process_to_run.empty())
192 smx_actor_t first_actor = simix_global->process_to_run.front();
194 /* execute the first actor; it will chain to the others when using suspend() */
195 static_cast<SwappedContext*>(first_actor->context_)->resume();
199 /** Maestro wants to yield back to a given actor, so awake it on the current thread
201 * In parallel, it is only applied to the N first elements of the parmap array,
202 * where N is the amount of worker threads in the parmap.
203 * See SwappedContextFactory::run_all for details.
205 void SwappedContext::resume()
207 if (factory_->parallel_) {
208 // Save the thread number (my body) in an os-thread-specific area
209 worker_id_ = threads_working_.fetch_add(1, std::memory_order_relaxed);
210 // Save my current soul (either maestro, or one of the minions) in a permanent area
211 SwappedContext* worker_context = static_cast<SwappedContext*>(self());
212 workers_context_[worker_id_] = worker_context;
213 // Switch my soul and the actor's one
214 Context::set_current(this);
215 worker_context->swap_into(this);
216 // No body runs that soul anymore at this point, but it is stored in a safe place.
217 // When the executed actor will do a blocking action, SIMIX_process_yield() will call suspend(), below.
218 } else { // sequential execution
219 // Maestro is always the calling thread of this function (ie, self() == maestro)
220 SwappedContext* old = static_cast<SwappedContext*>(self());
221 Context::set_current(this);
222 old->swap_into(this);
226 /** The actor wants to yield back to maestro, because it is blocked in a simcall (ie in SIMIX_process_yield())
228 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
230 * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
231 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
232 * and directly forth to the next executable actor.
234 void SwappedContext::suspend()
236 if (factory_->parallel_) {
237 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
238 boost::optional<smx_actor_t> next_work = parmap_->next();
239 SwappedContext* next_context;
241 // There is a next soul to embody (ie, another executable actor)
242 XBT_DEBUG("Run next process");
243 next_context = static_cast<SwappedContext*>(next_work.get()->context_);
245 // All actors were run, go back to the parmap context
246 XBT_DEBUG("No more processes to run");
247 // worker_id_ is the identity of my body, stored in thread_local when starting the scheduling round
248 next_context = workers_context_[worker_id_];
249 // When given that soul, the body will wait for the next scheduling round
252 // Get the next soul to run, either from another actor or the initial minion's one
253 Context::set_current(next_context);
254 this->swap_into(next_context);
255 } else { // sequential execution
256 /* determine the next context */
257 SwappedContext* next_context;
258 unsigned long int i = factory_->process_index_;
259 factory_->process_index_++;
261 if (i < simix_global->process_to_run.size()) {
262 /* Actually swap into the next actor directly without transiting to maestro */
263 XBT_DEBUG("Run next process");
264 next_context = static_cast<SwappedContext*>(simix_global->process_to_run[i]->context_);
266 /* all processes were run, actually return to maestro */
267 XBT_DEBUG("No more process to run");
268 next_context = static_cast<SwappedContext*>(get_maestro());
270 Context::set_current(next_context);
271 this->swap_into(next_context);
275 } // namespace context
276 } // namespace kernel
277 } // namespace simgrid