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 /* rank of the execution thread */
39 thread_local uintptr_t SwappedContext::worker_id_; /* thread-specific storage for the thread id */
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)
44 workers_context_.resize(parallel_ ? SIMIX_context_get_nthreads() : 1, nullptr);
47 SwappedContext::SwappedContext(std::function<void()>&& code, smx_actor_t actor, SwappedContextFactory* factory)
48 : Context(std::move(code), actor), factory_(factory)
50 // Save maestro (=context created first) in preparation for run_all
51 if (not factory->parallel_ && factory_->workers_context_[0] == nullptr)
52 factory_->workers_context_[0] = this;
55 xbt_assert((smx_context_stack_size & 0xf) == 0, "smx_context_stack_size should be multiple of 16");
56 if (smx_context_guard_size > 0 && not MC_is_active()) {
58 #if !defined(PTH_STACKGROWTH) || (PTH_STACKGROWTH != -1)
60 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
62 "Please disable stack guards with --cfg=contexts:guard-size:0");
63 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
64 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
67 size_t size = smx_context_stack_size + smx_context_guard_size;
69 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
70 * pointer returned by xbt_malloc0. */
71 unsigned char* alloc = static_cast<unsigned char*>(xbt_malloc0(size + xbt_pagesize));
72 stack_ = alloc - (reinterpret_cast<uintptr_t>(alloc) & (xbt_pagesize - 1)) + xbt_pagesize;
73 reinterpret_cast<unsigned char**>(stack_)[-1] = alloc;
74 #elif !defined(_WIN32)
76 if (posix_memalign(&alloc, xbt_pagesize, size) != 0)
77 xbt_die("Failed to allocate stack.");
78 this->stack_ = static_cast<unsigned char*>(alloc);
80 this->stack_ = static_cast<unsigned char*>(_aligned_malloc(size, xbt_pagesize));
84 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
86 "Failed to protect stack: %s.\n"
87 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
88 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
90 "https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization for more "
93 /* This is fatal. We are going to fail at some point when we try reusing this. */
96 this->stack_ = this->stack_ + smx_context_guard_size;
98 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(smx_context_stack_size));
101 #if PTH_STACKGROWTH == -1
102 ASAN_ONLY(this->asan_stack_ = this->stack_ + smx_context_stack_size);
104 ASAN_ONLY(this->asan_stack_ = this->stack_);
107 if (RUNNING_ON_VALGRIND)
108 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + smx_context_stack_size);
113 SwappedContext::~SwappedContext()
115 if (stack_ == nullptr) // maestro has no extra stack
119 if (RUNNING_ON_VALGRIND)
120 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
124 if (smx_context_guard_size > 0 && not MC_is_active()) {
125 stack_ = stack_ - smx_context_guard_size;
126 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
127 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
128 /* try to pursue anyway */
131 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
132 stack_ = reinterpret_cast<unsigned char**>(stack_)[-1];
135 #endif /* not windows */
140 unsigned char* SwappedContext::get_stack()
145 void SwappedContext::stop()
148 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
149 throw ForcefulKillException();
152 /** Maestro wants to run all ready actors */
153 void SwappedContextFactory::run_all()
155 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
156 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
157 * for the ones of the simulated processes that must run.
160 threads_working_ = 0;
162 // We lazily create the parmap so that all options are actually processed when doing so.
163 if (parmap_ == nullptr)
165 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_.get());
178 simix_global->actors_to_run);
179 } else { // sequential execution
180 if (simix_global->actors_to_run.empty())
183 /* maestro is already saved in the first slot of workers_context_ */
184 smx_actor_t first_actor = simix_global->actors_to_run.front();
186 /* execute the first actor; it will chain to the others when using suspend() */
187 static_cast<SwappedContext*>(first_actor->context_.get())->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, ActorImpl::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 (i.e., in ActorImpl::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_.get());
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->actors_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->actors_to_run[i]->context_.get());
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