1 /* Copyright (c) 2009-2021. 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/simix/smx_private.hpp"
11 #include "xbt/parmap.hpp"
13 #include "src/kernel/context/ContextSwapped.hpp"
25 #define _aligned_malloc __mingw_aligned_malloc
26 #define _aligned_free __mingw_aligned_free
30 #include <valgrind/valgrind.h>
32 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
33 #include <sanitizer/asan_interface.h>
35 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
36 #include <sanitizer/tsan_interface.h>
39 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
41 // The name of this function is currently hardcoded in MC (as string).
42 // Do not change it without fixing those references as well.
43 void smx_ctx_wrapper(simgrid::kernel::context::SwappedContext* context)
45 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
46 __sanitizer_finish_switch_fiber(nullptr, &context->asan_ctx_->asan_stack_, &context->asan_ctx_->asan_stack_size_);
50 context->Context::stop();
51 } catch (simgrid::ForcefulKillException const&) {
52 XBT_DEBUG("Caught a ForcefulKillException");
53 } catch (simgrid::Exception const& e) {
54 XBT_INFO("Actor killed by an uncaught exception %s", simgrid::xbt::demangle(typeid(e).name()).get());
57 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
58 context->asan_stop_ = true;
68 /* thread-specific storage for the worker's context */
69 thread_local SwappedContext* SwappedContext::worker_context_ = nullptr;
71 SwappedContext::SwappedContext(std::function<void()>&& code, smx_actor_t actor, SwappedContextFactory* factory)
72 : Context(std::move(code), actor), factory_(*factory)
74 // Save maestro (=first created context) in preparation for run_all
75 if (not SIMIX_context_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 (smx_context_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() + smx_context_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 if (posix_memalign(&alloc, xbt_pagesize, size) != 0)
100 xbt_die("Failed to allocate stack.");
101 this->stack_ = static_cast<unsigned char*>(alloc);
103 this->stack_ = static_cast<unsigned char*>(_aligned_malloc(size, xbt_pagesize));
107 if (mprotect(this->stack_, smx_context_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"
113 "https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization for more "
116 /* This is fatal. We are going to fail at some point when we try reusing this. */
119 this->stack_ = this->stack_ + smx_context_guard_size;
121 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(actor->get_stacksize()));
125 if (RUNNING_ON_VALGRIND)
126 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + actor->get_stacksize());
128 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
129 this->asan_stack_ = get_stack_bottom();
131 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
132 this->tsan_fiber_ = __tsan_create_fiber(0);
135 // not has_code(): in maestro context
136 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
137 this->tsan_fiber_ = __tsan_get_current_fiber();
142 SwappedContext::~SwappedContext()
144 if (stack_ == nullptr) // maestro has no extra stack
147 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
148 __tsan_destroy_fiber(tsan_fiber_);
151 if (RUNNING_ON_VALGRIND)
152 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
156 if (smx_context_guard_size > 0 && not MC_is_active()) {
157 stack_ = stack_ - smx_context_guard_size;
158 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
159 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
160 /* try to pursue anyway */
163 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
164 stack_ = reinterpret_cast<unsigned char**>(stack_)[-1];
167 #endif /* not windows */
172 unsigned char* SwappedContext::get_stack_bottom() const
174 // Depending on the stack direction, its bottom (that make_fcontext needs) may be the lower or higher end
175 #if PTH_STACKGROWTH == 1
178 return stack_ + get_actor()->get_stacksize();
182 void SwappedContext::stop()
185 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
186 throw ForcefulKillException();
189 void SwappedContext::swap_into(SwappedContext* to)
191 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
192 void* fake_stack = nullptr;
193 to->asan_ctx_ = this;
194 __sanitizer_start_switch_fiber(this->asan_stop_ ? nullptr : &fake_stack, to->asan_stack_, to->asan_stack_size_);
196 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
197 __tsan_switch_to_fiber(to->tsan_fiber_, 0);
200 swap_into_for_real(to);
202 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
203 __sanitizer_finish_switch_fiber(fake_stack, &this->asan_ctx_->asan_stack_, &this->asan_ctx_->asan_stack_size_);
207 /** Maestro wants to run all ready actors */
208 void SwappedContextFactory::run_all()
210 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
211 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
212 * for the ones of the simulated processes that must run.
214 if (SIMIX_context_is_parallel()) {
215 // We lazily create the parmap so that all options are actually processed when doing so.
216 if (parmap_ == nullptr)
217 parmap_ = std::make_unique<simgrid::xbt::Parmap<smx_actor_t>>(SIMIX_context_get_nthreads(),
218 SIMIX_context_get_parallel_mode());
220 // Usually, Parmap::apply() executes the provided function on all elements of the array.
221 // Here, the executed function does not return the control to the parmap before all the array is processed:
222 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
223 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
224 // It only yields back to worker_context when the work array is exhausted.
225 // - So, resume() is only launched from the parmap for the first job of each minion.
227 [](const actor::ActorImpl* process) {
228 auto* context = static_cast<SwappedContext*>(process->context_.get());
231 simix_global->actors_to_run);
232 } else { // sequential execution
233 if (simix_global->actors_to_run.empty())
236 /* maestro is already saved in the first slot of workers_context_ */
237 const actor::ActorImpl* first_actor = simix_global->actors_to_run.front();
239 /* execute the first actor; it will chain to the others when using suspend() */
240 static_cast<SwappedContext*>(first_actor->context_.get())->resume();
244 /** Maestro wants to yield back to a given actor, so awake it on the current thread
246 * In parallel, it is only applied to the N first elements of the parmap array,
247 * where N is the amount of worker threads in the parmap.
248 * See SwappedContextFactory::run_all for details.
250 void SwappedContext::resume()
252 auto* old = static_cast<SwappedContext*>(self());
253 if (SIMIX_context_is_parallel()) {
254 // Save my current soul (either maestro, or one of the minions) in a thread-specific area
255 worker_context_ = old;
257 // Switch my soul and the actor's one
258 Context::set_current(this);
259 old->swap_into(this);
260 // No body runs that soul anymore at this point, but it is stored in a safe place.
261 // When the executed actor will do a blocking action, ActorImpl::yield() will call suspend(), below.
264 /** The actor wants to yield back to maestro, because it is blocked in a simcall (i.e., in ActorImpl::yield())
266 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
268 * This makes the parmap::apply awkward (see SwappedContextFactory::run_all()) because it only apply regularly
269 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
270 * and directly forth to the next executable actor.
272 void SwappedContext::suspend()
274 SwappedContext* next_context;
275 if (SIMIX_context_is_parallel()) {
276 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
277 boost::optional<smx_actor_t> next_work = factory_.parmap_->next();
279 // There is a next soul to embody (ie, another executable actor)
280 XBT_DEBUG("Run next process");
281 next_context = static_cast<SwappedContext*>(next_work.get()->context_.get());
283 // All actors were run, go back to the parmap context
284 XBT_DEBUG("No more actors to run");
285 // worker_context_ is my own soul, stored in thread_local when starting the scheduling round
286 next_context = worker_context_;
287 // When given that soul, the body will wait for the next scheduling round
289 } else { // sequential execution
290 /* determine the next context */
291 unsigned long int i = factory_.process_index_;
292 factory_.process_index_++;
294 if (i < simix_global->actors_to_run.size()) {
295 /* Actually swap into the next actor directly without transiting to maestro */
296 XBT_DEBUG("Run next actor");
297 next_context = static_cast<SwappedContext*>(simix_global->actors_to_run[i]->context_.get());
299 /* all processes were run, actually return to maestro */
300 XBT_DEBUG("No more actors to run");
301 next_context = factory_.maestro_context_;
304 Context::set_current(next_context);
305 this->swap_into(next_context);
308 } // namespace context
309 } // namespace kernel
310 } // namespace simgrid