1 /* Copyright (c) 2009-2020. 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 SwappedContext::SwappedContext(std::function<void()>&& code, smx_actor_t actor, SwappedContextFactory* factory)
42 : Context(std::move(code), actor), factory_(*factory)
44 // Save maestro (=context created first) in preparation for run_all
45 if (not SIMIX_context_is_parallel() && factory_.maestro_context_ == nullptr)
46 factory_.maestro_context_ = this;
49 xbt_assert((smx_context_stack_size & 0xf) == 0, "smx_context_stack_size should be multiple of 16");
50 if (smx_context_guard_size > 0 && not MC_is_active()) {
51 #if PTH_STACKGROWTH != -1
53 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
55 "Please disable stack guards with --cfg=contexts:guard-size:0");
56 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
57 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
60 size_t size = smx_context_stack_size + smx_context_guard_size;
62 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
63 * pointer returned by xbt_malloc0. */
64 unsigned char* alloc = static_cast<unsigned char*>(xbt_malloc0(size + xbt_pagesize));
65 stack_ = alloc - (reinterpret_cast<uintptr_t>(alloc) & (xbt_pagesize - 1)) + xbt_pagesize;
66 reinterpret_cast<unsigned char**>(stack_)[-1] = alloc;
67 #elif !defined(_WIN32)
69 if (posix_memalign(&alloc, xbt_pagesize, size) != 0)
70 xbt_die("Failed to allocate stack.");
71 this->stack_ = static_cast<unsigned char*>(alloc);
73 this->stack_ = static_cast<unsigned char*>(_aligned_malloc(size, xbt_pagesize));
77 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
79 "Failed to protect stack: %s.\n"
80 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
81 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
83 "https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization for more "
86 /* This is fatal. We are going to fail at some point when we try reusing this. */
89 this->stack_ = this->stack_ + smx_context_guard_size;
91 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(smx_context_stack_size));
95 if (RUNNING_ON_VALGRIND)
96 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + smx_context_stack_size);
98 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
99 this->asan_stack_ = get_stack_bottom();
104 SwappedContext::~SwappedContext()
106 if (stack_ == nullptr) // maestro has no extra stack
110 if (RUNNING_ON_VALGRIND)
111 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
115 if (smx_context_guard_size > 0 && not MC_is_active()) {
116 stack_ = stack_ - smx_context_guard_size;
117 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
118 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
119 /* try to pursue anyway */
122 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
123 stack_ = reinterpret_cast<unsigned char**>(stack_)[-1];
126 #endif /* not windows */
131 void SwappedContext::stop()
134 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
135 throw ForcefulKillException();
138 /** Maestro wants to run all ready actors */
139 void SwappedContextFactory::run_all()
141 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
142 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
143 * for the ones of the simulated processes that must run.
145 if (SIMIX_context_is_parallel()) {
146 // We lazily create the parmap so that all options are actually processed when doing so.
147 if (parmap_ == nullptr)
149 new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode()));
151 // Usually, Parmap::apply() executes the provided function on all elements of the array.
152 // Here, the executed function does not return the control to the parmap before all the array is processed:
153 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
154 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
155 // It only yields back to worker_context when the work array is exhausted.
156 // - So, resume() is only launched from the parmap for the first job of each minion.
158 [](const actor::ActorImpl* process) {
159 SwappedContext* context = static_cast<SwappedContext*>(process->context_.get());
162 simix_global->actors_to_run);
163 } else { // sequential execution
164 if (simix_global->actors_to_run.empty())
167 /* maestro is already saved in the first slot of workers_context_ */
168 const actor::ActorImpl* first_actor = simix_global->actors_to_run.front();
170 /* execute the first actor; it will chain to the others when using suspend() */
171 static_cast<SwappedContext*>(first_actor->context_.get())->resume();
175 /** Maestro wants to yield back to a given actor, so awake it on the current thread
177 * In parallel, it is only applied to the N first elements of the parmap array,
178 * where N is the amount of worker threads in the parmap.
179 * See SwappedContextFactory::run_all for details.
181 void SwappedContext::resume()
183 SwappedContext* old = static_cast<SwappedContext*>(self());
184 if (SIMIX_context_is_parallel()) {
185 // Save my current soul (either maestro, or one of the minions) in a thread-specific area
186 worker_context_ = old;
188 // Switch my soul and the actor's one
189 Context::set_current(this);
190 old->swap_into(this);
191 // No body runs that soul anymore at this point, but it is stored in a safe place.
192 // When the executed actor will do a blocking action, ActorImpl::yield() will call suspend(), below.
195 /** The actor wants to yield back to maestro, because it is blocked in a simcall (i.e., in ActorImpl::yield())
197 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
199 * This makes the parmap::apply awkward (see SwappedContextFactory::run_all()) because it only apply regularly
200 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
201 * and directly forth to the next executable actor.
203 void SwappedContext::suspend()
205 SwappedContext* next_context;
206 if (SIMIX_context_is_parallel()) {
207 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
208 boost::optional<smx_actor_t> next_work = factory_.parmap_->next();
210 // There is a next soul to embody (ie, another executable actor)
211 XBT_DEBUG("Run next process");
212 next_context = static_cast<SwappedContext*>(next_work.get()->context_.get());
214 // All actors were run, go back to the parmap context
215 XBT_DEBUG("No more actors to run");
216 // worker_context_ is my own soul, stored in thread_local when starting the scheduling round
217 next_context = worker_context_;
218 // When given that soul, the body will wait for the next scheduling round
220 } else { // sequential execution
221 /* determine the next context */
222 unsigned long int i = factory_.process_index_;
223 factory_.process_index_++;
225 if (i < simix_global->actors_to_run.size()) {
226 /* Actually swap into the next actor directly without transiting to maestro */
227 XBT_DEBUG("Run next actor");
228 next_context = static_cast<SwappedContext*>(simix_global->actors_to_run[i]->context_.get());
230 /* all processes were run, actually return to maestro */
231 XBT_DEBUG("No more actors to run");
232 next_context = factory_.maestro_context_;
235 Context::set_current(next_context);
236 this->swap_into(next_context);
239 } // namespace context
240 } // namespace kernel
241 } // namespace simgrid