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/Exception.hpp"
7 #include "simgrid/modelchecker.h"
8 #include "src/internal_config.h"
9 #include "src/kernel/actor/ActorImpl.hpp"
10 #include "src/kernel/context/context_private.hpp"
11 #include "src/simix/smx_private.hpp"
12 #include "xbt/parmap.hpp"
14 #include "src/kernel/context/ContextSwapped.hpp"
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 /* thread-specific storage for the worker's context */
39 thread_local SwappedContext* SwappedContext::worker_context_ = nullptr;
41 SwappedContextFactory::SwappedContextFactory() : ContextFactory(), parallel_(SIMIX_context_is_parallel())
43 parmap_ = nullptr; // will be created lazily with the right parameters if needed (ie, in parallel)
46 SwappedContext::SwappedContext(std::function<void()>&& code, smx_actor_t actor, SwappedContextFactory* factory)
47 : Context(std::move(code), actor), factory_(factory)
49 // Save maestro (=context created first) in preparation for run_all
50 if (not factory->parallel_ && factory->maestro_context_ == nullptr)
51 factory->maestro_context_ = this;
54 xbt_assert((smx_context_stack_size & 0xf) == 0, "smx_context_stack_size should be multiple of 16");
55 if (smx_context_guard_size > 0 && not MC_is_active()) {
57 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
59 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
61 "Please disable stack guards with --cfg=contexts:guard-size:0");
62 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
63 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
66 size_t size = smx_context_stack_size + smx_context_guard_size;
68 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
69 * pointer returned by xbt_malloc0. */
70 unsigned char* alloc = static_cast<unsigned char*>(xbt_malloc0(size + xbt_pagesize));
71 stack_ = alloc - (reinterpret_cast<uintptr_t>(alloc) & (xbt_pagesize - 1)) + xbt_pagesize;
72 reinterpret_cast<unsigned char**>(stack_)[-1] = alloc;
73 #elif !defined(_WIN32)
75 if (posix_memalign(&alloc, xbt_pagesize, size) != 0)
76 xbt_die("Failed to allocate stack.");
77 this->stack_ = static_cast<unsigned char*>(alloc);
79 this->stack_ = static_cast<unsigned char*>(_aligned_malloc(size, xbt_pagesize));
83 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
85 "Failed to protect stack: %s.\n"
86 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
87 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
89 "https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization for more "
92 /* This is fatal. We are going to fail at some point when we try reusing this. */
95 this->stack_ = this->stack_ + smx_context_guard_size;
97 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(smx_context_stack_size));
100 #if PTH_STACKGROWTH == -1
101 ASAN_ONLY(this->asan_stack_ = this->stack_ + smx_context_stack_size);
103 ASAN_ONLY(this->asan_stack_ = this->stack_);
106 if (RUNNING_ON_VALGRIND)
107 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + smx_context_stack_size);
112 SwappedContext::~SwappedContext()
114 if (stack_ == nullptr) // maestro has no extra stack
118 if (RUNNING_ON_VALGRIND)
119 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
123 if (smx_context_guard_size > 0 && not MC_is_active()) {
124 stack_ = stack_ - smx_context_guard_size;
125 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
126 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
127 /* try to pursue anyway */
130 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
131 stack_ = reinterpret_cast<unsigned char**>(stack_)[-1];
134 #endif /* not windows */
139 unsigned char* SwappedContext::get_stack()
144 void SwappedContext::stop()
147 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
148 throw ForcefulKillException();
151 /** Maestro wants to run all ready actors */
152 void SwappedContextFactory::run_all()
154 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
155 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
156 * for the ones of the simulated processes that must run.
159 // We lazily create the parmap so that all options are actually processed when doing so.
160 if (parmap_ == nullptr)
162 new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode()));
164 // Usually, Parmap::apply() executes the provided function on all elements of the array.
165 // Here, the executed function does not return the control to the parmap before all the array is processed:
166 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
167 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
168 // It only yields back to worker_context when the work array is exhausted.
169 // - So, resume() is only launched from the parmap for the first job of each minion.
171 [](smx_actor_t process) {
172 SwappedContext* context = static_cast<SwappedContext*>(process->context_.get());
175 simix_global->actors_to_run);
176 } else { // sequential execution
177 if (simix_global->actors_to_run.empty())
180 /* maestro is already saved in the first slot of workers_context_ */
181 smx_actor_t first_actor = simix_global->actors_to_run.front();
183 /* execute the first actor; it will chain to the others when using suspend() */
184 static_cast<SwappedContext*>(first_actor->context_.get())->resume();
188 /** Maestro wants to yield back to a given actor, so awake it on the current thread
190 * In parallel, it is only applied to the N first elements of the parmap array,
191 * where N is the amount of worker threads in the parmap.
192 * See SwappedContextFactory::run_all for details.
194 void SwappedContext::resume()
196 if (factory_->parallel_) {
197 // Save my current soul (either maestro, or one of the minions) in a thread-specific area
198 worker_context_ = static_cast<SwappedContext*>(self());
199 // Switch my soul and the actor's one
200 Context::set_current(this);
201 worker_context_->swap_into(this);
202 // No body runs that soul anymore at this point, but it is stored in a safe place.
203 // When the executed actor will do a blocking action, ActorImpl::yield() will call suspend(), below.
204 } else { // sequential execution
205 SwappedContext* old = static_cast<SwappedContext*>(self());
206 Context::set_current(this);
207 old->swap_into(this);
211 /** The actor wants to yield back to maestro, because it is blocked in a simcall (i.e., in ActorImpl::yield())
213 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
215 * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
216 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
217 * and directly forth to the next executable actor.
219 void SwappedContext::suspend()
221 if (factory_->parallel_) {
222 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
223 boost::optional<smx_actor_t> next_work = factory_->parmap_->next();
224 SwappedContext* next_context;
226 // There is a next soul to embody (ie, another executable actor)
227 XBT_DEBUG("Run next process");
228 next_context = static_cast<SwappedContext*>(next_work.get()->context_.get());
230 // All actors were run, go back to the parmap context
231 XBT_DEBUG("No more actors to run");
232 // worker_context_ is my own soul, stored in thread_local when starting the scheduling round
233 next_context = worker_context_;
234 // When given that soul, the body will wait for the next scheduling round
237 // Get the next soul to run, either from another actor or the initial minion's one
238 Context::set_current(next_context);
239 this->swap_into(next_context);
241 } else { // sequential execution
242 /* determine the next context */
243 SwappedContext* next_context;
244 unsigned long int i = factory_->process_index_;
245 factory_->process_index_++;
247 if (i < simix_global->actors_to_run.size()) {
248 /* Actually swap into the next actor directly without transiting to maestro */
249 XBT_DEBUG("Run next actor");
250 next_context = static_cast<SwappedContext*>(simix_global->actors_to_run[i]->context_.get());
252 /* all processes were run, actually return to maestro */
253 XBT_DEBUG("No more actors to run");
254 next_context = factory_->maestro_context_;
256 Context::set_current(next_context);
257 this->swap_into(next_context);
261 } // namespace context
262 } // namespace kernel
263 } // namespace simgrid