1 /* Copyright (c) 2009-2023. 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/EngineImpl.hpp"
10 #include "src/kernel/actor/ActorImpl.hpp"
11 #include "src/sthread/sthread.h"
12 #include "src/xbt/parmap.hpp"
14 #include "src/kernel/context/ContextSwapped.hpp"
16 #include <boost/core/demangle.hpp>
22 #include <valgrind/valgrind.h>
24 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
25 #include <sanitizer/asan_interface.h>
27 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
28 #include <sanitizer/tsan_interface.h>
31 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(ker_context);
33 // The name of this function is currently hardcoded in MC (as string).
34 // Do not change it without fixing those references as well.
35 void smx_ctx_wrapper(simgrid::kernel::context::SwappedContext* context)
37 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
38 __sanitizer_finish_switch_fiber(nullptr, &context->asan_ctx_->asan_stack_, &context->asan_ctx_->asan_stack_size_);
45 } catch (simgrid::ForcefulKillException const&) {
47 XBT_DEBUG("Caught a ForcefulKillException");
48 } catch (simgrid::Exception const& e) {
50 XBT_INFO("Actor killed by an uncaught exception %s", boost::core::demangle(typeid(e).name()).c_str());
53 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
54 context->asan_stop_ = true;
60 namespace simgrid::kernel::context {
62 /* thread-specific storage for the worker's context */
63 thread_local SwappedContext* SwappedContext::worker_context_ = nullptr;
65 SwappedContext::SwappedContext(std::function<void()>&& code, actor::ActorImpl* actor, SwappedContextFactory* factory)
66 : Context(std::move(code), actor, not code /* maestro if no code */), factory_(*factory)
68 // Save maestro (=first created context) in preparation for run_all
69 if (not is_parallel() && factory_.maestro_context_ == nullptr)
70 factory_.maestro_context_ = this;
73 xbt_assert((actor->get_stacksize() & 0xf) == 0, "Actor stack size should be multiple of 16");
74 if (guard_size > 0 && not MC_is_active()) {
75 #if PTH_STACKGROWTH != -1
77 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
79 "Please disable stack guards with --cfg=contexts:guard-size:0");
80 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
81 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
84 size_t size = actor->get_stacksize() + guard_size;
86 xbt_assert(posix_memalign(&alloc, xbt_pagesize, size) == 0, "Failed to allocate stack.");
87 this->stack_ = static_cast<unsigned char*>(alloc);
89 /* This is fatal. We are going to fail at some point when we try reusing this. */
91 mprotect(this->stack_, guard_size, PROT_NONE) != -1,
92 "Failed to protect stack: %s.\n"
93 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
94 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
95 "Please see https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization "
96 "for more information.",
99 this->stack_ = this->stack_ + guard_size;
101 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(actor->get_stacksize()));
105 if (RUNNING_ON_VALGRIND)
106 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + actor->get_stacksize());
108 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
109 this->asan_stack_ = get_stack_bottom();
111 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
112 this->tsan_fiber_ = __tsan_create_fiber(0);
115 // not has_code(): in maestro context
116 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
117 this->tsan_fiber_ = __tsan_get_current_fiber();
122 SwappedContext::~SwappedContext()
124 if (stack_ == nullptr) // maestro has no extra stack
127 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
128 __tsan_destroy_fiber(tsan_fiber_);
131 if (valgrind_stack_id_ != 0)
132 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
135 if (guard_size > 0 && not MC_is_active()) {
136 stack_ = stack_ - guard_size;
137 if (mprotect(stack_, guard_size, PROT_READ | PROT_WRITE) == -1) {
138 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
139 /* try to pursue anyway */
146 unsigned char* SwappedContext::get_stack_bottom() const
148 // Depending on the stack direction, its bottom (that make_fcontext needs) may be the lower or higher end
149 #if PTH_STACKGROWTH == 1
152 return stack_ + get_actor()->get_stacksize();
156 void SwappedContext::swap_into(SwappedContext* to)
158 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
159 void* fake_stack = nullptr;
160 to->asan_ctx_ = this;
161 __sanitizer_start_switch_fiber(this->asan_stop_ ? nullptr : &fake_stack, to->asan_stack_, to->asan_stack_size_);
163 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
164 __tsan_switch_to_fiber(to->tsan_fiber_, 0);
167 swap_into_for_real(to);
169 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
170 __sanitizer_finish_switch_fiber(fake_stack, &this->asan_ctx_->asan_stack_, &this->asan_ctx_->asan_stack_size_);
174 /** Maestro wants to run all ready actors */
175 void SwappedContextFactory::run_all(std::vector<actor::ActorImpl*> const& actors_list)
177 const auto* engine = EngineImpl::get_instance();
178 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
179 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
180 * for the ones of the simulated processes that must run.
182 if (Context::is_parallel()) {
183 // We lazily create the parmap so that all options are actually processed when doing so.
184 if (parmap_ == nullptr)
186 std::make_unique<simgrid::xbt::Parmap<actor::ActorImpl*>>(Context::get_nthreads(), Context::parallel_mode);
188 // Usually, Parmap::apply() executes the provided function on all elements of the array.
189 // Here, the executed function does not return the control to the parmap before all the array is processed:
190 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
191 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
192 // It only yields back to worker_context when the work array is exhausted.
193 // - So, resume() is only launched from the parmap for the first job of each minion.
195 [](const actor::ActorImpl* actor) {
196 auto* context = static_cast<SwappedContext*>(actor->context_.get());
200 } else { // sequential execution
201 if (actors_list.empty())
204 /* maestro is already saved in the first slot of workers_context_ */
205 const actor::ActorImpl* first_actor = engine->get_first_actor_to_run();
207 /* execute the first actor; it will chain to the others when using suspend() */
208 static_cast<SwappedContext*>(first_actor->context_.get())->resume();
212 /** Maestro wants to yield back to a given actor, so awake it on the current thread
214 * In parallel, it is only applied to the N first elements of the parmap array,
215 * where N is the amount of worker threads in the parmap.
216 * See SwappedContextFactory::run_all for details.
218 void SwappedContext::resume()
220 auto* old = static_cast<SwappedContext*>(self());
222 // Save my current soul (either maestro, or one of the minions) in a thread-specific area
223 worker_context_ = old;
226 // Switch my soul and the actor's one
227 Context::set_current(this);
228 old->swap_into(this);
229 // No body runs that soul anymore at this point, but it is stored in a safe place.
230 // When the executed actor will do a blocking action, ActorImpl::yield() will call suspend(), below.
233 /** The actor wants to yield back to maestro, because it is blocked in a simcall (i.e., in ActorImpl::yield())
235 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
237 * This makes the parmap::apply awkward (see SwappedContextFactory::run_all()) because it only apply regularly
238 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
239 * and directly forth to the next executable actor.
241 void SwappedContext::suspend()
243 SwappedContext* next_context;
245 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
246 boost::optional<actor::ActorImpl*> next_work = factory_.parmap_->next();
248 // There is a next soul to embody (ie, another executable actor)
249 XBT_DEBUG("Run next process");
250 next_context = static_cast<SwappedContext*>(next_work.get()->context_.get());
252 // All actors were run, go back to the parmap context
253 XBT_DEBUG("No more actors to run");
254 // worker_context_ is my own soul, stored in thread_local when starting the scheduling round
255 next_context = worker_context_;
256 // When given that soul, the body will wait for the next scheduling round
258 } else { // sequential execution
259 const auto* engine = EngineImpl::get_instance();
260 /* determine the next context */
261 unsigned long int i = factory_.process_index_;
262 factory_.process_index_++;
264 if (i < engine->get_actor_to_run_count()) {
265 /* Actually swap into the next actor directly without transiting to maestro */
266 XBT_DEBUG("Run next actor");
268 next_context = static_cast<SwappedContext*>(engine->get_actor_to_run_at(i)->context_.get());
270 /* all processes were run, actually return to maestro */
271 XBT_DEBUG("No more actors to run");
273 next_context = factory_.maestro_context_;
276 Context::set_current(next_context);
277 this->swap_into(next_context);
280 } // namespace simgrid::kernel::context