1 /* Copyright (c) 2009-2022. 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 "xbt/parmap.hpp"
13 #include "src/kernel/context/ContextSwapped.hpp"
15 #include <boost/core/demangle.hpp>
27 #define _aligned_malloc __mingw_aligned_malloc
28 #define _aligned_free __mingw_aligned_free
32 #include <valgrind/valgrind.h>
34 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
35 #include <sanitizer/asan_interface.h>
37 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
38 #include <sanitizer/tsan_interface.h>
41 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(ker_context);
43 // The name of this function is currently hardcoded in MC (as string).
44 // Do not change it without fixing those references as well.
45 void smx_ctx_wrapper(simgrid::kernel::context::SwappedContext* context)
47 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
48 __sanitizer_finish_switch_fiber(nullptr, &context->asan_ctx_->asan_stack_, &context->asan_ctx_->asan_stack_size_);
53 } catch (simgrid::ForcefulKillException const&) {
54 XBT_DEBUG("Caught a ForcefulKillException");
55 } catch (simgrid::Exception const& e) {
56 XBT_INFO("Actor killed by an uncaught exception %s", boost::core::demangle(typeid(e).name()).c_str());
59 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
60 context->asan_stop_ = true;
66 namespace simgrid::kernel::context {
68 /* thread-specific storage for the worker's context */
69 thread_local SwappedContext* SwappedContext::worker_context_ = nullptr;
71 SwappedContext::SwappedContext(std::function<void()>&& code, actor::ActorImpl* actor, SwappedContextFactory* factory)
72 : Context(std::move(code), actor, not code /* maestro if no code */), factory_(*factory)
74 // Save maestro (=first created context) in preparation for run_all
75 if (not is_parallel() && factory_.maestro_context_ == nullptr)
76 factory_.maestro_context_ = this;
79 xbt_assert((actor->get_stacksize() & 0xf) == 0, "Actor stack size should be multiple of 16");
80 if (guard_size > 0 && not MC_is_active()) {
81 #if PTH_STACKGROWTH != -1
83 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
85 "Please disable stack guards with --cfg=contexts:guard-size:0");
86 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
87 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
90 size_t size = actor->get_stacksize() + guard_size;
92 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
93 * pointer returned by xbt_malloc0. */
94 auto* alloc = static_cast<unsigned char*>(xbt_malloc0(size + xbt_pagesize));
95 stack_ = alloc - (reinterpret_cast<uintptr_t>(alloc) & (xbt_pagesize - 1)) + xbt_pagesize;
96 reinterpret_cast<unsigned char**>(stack_)[-1] = alloc;
97 #elif !defined(_WIN32)
99 xbt_assert(posix_memalign(&alloc, xbt_pagesize, size) == 0, "Failed to allocate stack.");
100 this->stack_ = static_cast<unsigned char*>(alloc);
102 this->stack_ = static_cast<unsigned char*>(_aligned_malloc(size, xbt_pagesize));
106 /* This is fatal. We are going to fail at some point when we try reusing this. */
108 mprotect(this->stack_, guard_size, PROT_NONE) != -1,
109 "Failed to protect stack: %s.\n"
110 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
111 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
112 "Please see https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization "
113 "for more information.",
116 this->stack_ = this->stack_ + guard_size;
118 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(actor->get_stacksize()));
122 if (RUNNING_ON_VALGRIND)
123 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + actor->get_stacksize());
125 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
126 this->asan_stack_ = get_stack_bottom();
128 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
129 this->tsan_fiber_ = __tsan_create_fiber(0);
132 // not has_code(): in maestro context
133 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
134 this->tsan_fiber_ = __tsan_get_current_fiber();
139 SwappedContext::~SwappedContext()
141 if (stack_ == nullptr) // maestro has no extra stack
144 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
145 __tsan_destroy_fiber(tsan_fiber_);
148 if (valgrind_stack_id_ != 0)
149 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
153 if (guard_size > 0 && not MC_is_active()) {
154 stack_ = stack_ - guard_size;
155 if (mprotect(stack_, guard_size, PROT_READ | PROT_WRITE) == -1) {
156 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
157 /* try to pursue anyway */
160 /* Retrieve the saved pointer. See the initialization above. */
161 stack_ = reinterpret_cast<unsigned char**>(stack_)[-1];
164 #endif /* not windows */
169 unsigned char* SwappedContext::get_stack_bottom() const
171 // Depending on the stack direction, its bottom (that make_fcontext needs) may be the lower or higher end
172 #if PTH_STACKGROWTH == 1
175 return stack_ + get_actor()->get_stacksize();
179 void SwappedContext::swap_into(SwappedContext* to)
181 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
182 void* fake_stack = nullptr;
183 to->asan_ctx_ = this;
184 __sanitizer_start_switch_fiber(this->asan_stop_ ? nullptr : &fake_stack, to->asan_stack_, to->asan_stack_size_);
186 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
187 __tsan_switch_to_fiber(to->tsan_fiber_, 0);
190 swap_into_for_real(to);
192 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
193 __sanitizer_finish_switch_fiber(fake_stack, &this->asan_ctx_->asan_stack_, &this->asan_ctx_->asan_stack_size_);
197 /** Maestro wants to run all ready actors */
198 void SwappedContextFactory::run_all(std::vector<actor::ActorImpl*> const& actors_list)
200 const auto* engine = EngineImpl::get_instance();
201 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
202 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
203 * for the ones of the simulated processes that must run.
206 // We lazily create the parmap so that all options are actually processed when doing so.
207 if (parmap_ == nullptr)
208 parmap_ = std::make_unique<simgrid::xbt::Parmap<actor::ActorImpl*>>(get_nthreads(), get_parallel_mode());
210 // Usually, Parmap::apply() executes the provided function on all elements of the array.
211 // Here, the executed function does not return the control to the parmap before all the array is processed:
212 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
213 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
214 // It only yields back to worker_context when the work array is exhausted.
215 // - So, resume() is only launched from the parmap for the first job of each minion.
217 [](const actor::ActorImpl* actor) {
218 auto* context = static_cast<SwappedContext*>(actor->context_.get());
222 } else { // sequential execution
223 if (actors_list.empty())
226 /* maestro is already saved in the first slot of workers_context_ */
227 const actor::ActorImpl* first_actor = engine->get_first_actor_to_run();
229 /* execute the first actor; it will chain to the others when using suspend() */
230 static_cast<SwappedContext*>(first_actor->context_.get())->resume();
234 /** Maestro wants to yield back to a given actor, so awake it on the current thread
236 * In parallel, it is only applied to the N first elements of the parmap array,
237 * where N is the amount of worker threads in the parmap.
238 * See SwappedContextFactory::run_all for details.
240 void SwappedContext::resume()
242 auto* old = static_cast<SwappedContext*>(self());
244 // Save my current soul (either maestro, or one of the minions) in a thread-specific area
245 worker_context_ = old;
247 // Switch my soul and the actor's one
248 Context::set_current(this);
249 old->swap_into(this);
250 // No body runs that soul anymore at this point, but it is stored in a safe place.
251 // When the executed actor will do a blocking action, ActorImpl::yield() will call suspend(), below.
254 /** The actor wants to yield back to maestro, because it is blocked in a simcall (i.e., in ActorImpl::yield())
256 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
258 * This makes the parmap::apply awkward (see SwappedContextFactory::run_all()) because it only apply regularly
259 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
260 * and directly forth to the next executable actor.
262 void SwappedContext::suspend()
264 SwappedContext* next_context;
266 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
267 boost::optional<actor::ActorImpl*> next_work = factory_.parmap_->next();
269 // There is a next soul to embody (ie, another executable actor)
270 XBT_DEBUG("Run next process");
271 next_context = static_cast<SwappedContext*>(next_work.get()->context_.get());
273 // All actors were run, go back to the parmap context
274 XBT_DEBUG("No more actors to run");
275 // worker_context_ is my own soul, stored in thread_local when starting the scheduling round
276 next_context = worker_context_;
277 // When given that soul, the body will wait for the next scheduling round
279 } else { // sequential execution
280 const auto* engine = EngineImpl::get_instance();
281 /* determine the next context */
282 unsigned long int i = factory_.process_index_;
283 factory_.process_index_++;
285 if (i < engine->get_actor_to_run_count()) {
286 /* Actually swap into the next actor directly without transiting to maestro */
287 XBT_DEBUG("Run next actor");
288 next_context = static_cast<SwappedContext*>(engine->get_actor_to_run_at(i)->context_.get());
290 /* all processes were run, actually return to maestro */
291 XBT_DEBUG("No more actors to run");
292 next_context = factory_.maestro_context_;
295 Context::set_current(next_context);
296 this->swap_into(next_context);
299 } // namespace simgrid::kernel::context