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 (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);
102 unsigned int valgrind_stack_id =
103 VALGRIND_STACK_REGISTER(this->stack_, (char*)this->stack_ + smx_context_stack_size);
104 memcpy((char*)this->stack_ + smx_context_usable_stack_size, &valgrind_stack_id, sizeof valgrind_stack_id);
109 SwappedContext::~SwappedContext()
111 if (stack_ == nullptr) // maestro has no extra stack
115 unsigned int valgrind_stack_id;
116 memcpy(&valgrind_stack_id, (char*)stack_ + smx_context_usable_stack_size, sizeof valgrind_stack_id);
117 VALGRIND_STACK_DEREGISTER(valgrind_stack_id);
121 if (smx_context_guard_size > 0 && not MC_is_active()) {
122 stack_ = (char*)stack_ - smx_context_guard_size;
123 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
124 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
125 /* try to pursue anyway */
128 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
129 stack_ = *((void**)stack_ - 1);
132 #endif /* not windows */
137 void* SwappedContext::get_stack()
142 void SwappedContext::stop()
145 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
149 /** Maestro wants to run all ready actors */
150 void SwappedContextFactory::run_all()
152 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
153 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
154 * for the ones of the simulated processes that must run.
157 threads_working_ = 0;
159 // We lazily create the parmap so that all options are actually processed when doing so.
160 if (parmap_ == nullptr)
161 parmap_ = new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
163 // Usually, Parmap::apply() executes the provided function on all elements of the array.
164 // Here, the executed function does not return the control to the parmap before all the array is processed:
165 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
166 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
167 // It only yields back to worker_context when the work array is exhausted.
168 // - So, resume() is only launched from the parmap for the first job of each minion.
170 [](smx_actor_t process) {
171 SwappedContext* context = static_cast<SwappedContext*>(process->context_);
174 simix_global->process_to_run);
175 } else { // sequential execution
176 if (simix_global->process_to_run.empty())
179 /* maestro is already saved in the first slot of workers_context_ */
180 smx_actor_t first_actor = simix_global->process_to_run.front();
182 /* execute the first actor; it will chain to the others when using suspend() */
183 static_cast<SwappedContext*>(first_actor->context_)->resume();
187 /** Maestro wants to yield back to a given actor, so awake it on the current thread
189 * In parallel, it is only applied to the N first elements of the parmap array,
190 * where N is the amount of worker threads in the parmap.
191 * See SwappedContextFactory::run_all for details.
193 void SwappedContext::resume()
195 if (factory_->parallel_) {
196 // Save the thread number (my body) in an os-thread-specific area
197 worker_id_ = factory_->threads_working_.fetch_add(1, std::memory_order_relaxed);
198 // Save my current soul (either maestro, or one of the minions) in a permanent area
199 SwappedContext* worker_context = static_cast<SwappedContext*>(self());
200 factory_->workers_context_[worker_id_] = worker_context;
201 // Switch my soul and the actor's one
202 Context::set_current(this);
203 worker_context->swap_into(this);
204 // No body runs that soul anymore at this point, but it is stored in a safe place.
205 // When the executed actor will do a blocking action, SIMIX_process_yield() will call suspend(), below.
206 } else { // sequential execution
207 SwappedContext* old = static_cast<SwappedContext*>(self());
208 Context::set_current(this);
209 old->swap_into(this);
213 /** The actor wants to yield back to maestro, because it is blocked in a simcall (ie in SIMIX_process_yield())
215 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
217 * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
218 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
219 * and directly forth to the next executable actor.
221 void SwappedContext::suspend()
223 if (factory_->parallel_) {
224 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
225 boost::optional<smx_actor_t> next_work = factory_->parmap_->next();
226 SwappedContext* next_context;
228 // There is a next soul to embody (ie, another executable actor)
229 XBT_DEBUG("Run next process");
230 next_context = static_cast<SwappedContext*>(next_work.get()->context_);
232 // All actors were run, go back to the parmap context
233 XBT_DEBUG("No more actors to run");
234 // worker_id_ is the identity of my body, stored in thread_local when starting the scheduling round
235 next_context = factory_->workers_context_[worker_id_];
236 // When given that soul, the body will wait for the next scheduling round
239 // Get the next soul to run, either from another actor or the initial minion's one
240 Context::set_current(next_context);
241 this->swap_into(next_context);
243 } else { // sequential execution
244 /* determine the next context */
245 SwappedContext* next_context;
246 unsigned long int i = factory_->process_index_;
247 factory_->process_index_++;
249 if (i < simix_global->process_to_run.size()) {
250 /* Actually swap into the next actor directly without transiting to maestro */
251 XBT_DEBUG("Run next actor");
252 next_context = static_cast<SwappedContext*>(simix_global->process_to_run[i]->context_);
254 /* all processes were run, actually return to maestro */
255 XBT_DEBUG("No more actors to run");
256 next_context = factory_->workers_context_[0];
258 Context::set_current(next_context);
259 this->swap_into(next_context);
263 } // namespace context
264 } // namespace kernel
265 } // namespace simgrid