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/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>
30 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
31 #include <sanitizer/asan_interface.h>
33 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
34 #include <sanitizer/tsan_interface.h>
37 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
39 // The name of this function is currently hardcoded in MC (as string).
40 // Do not change it without fixing those references as well.
41 void smx_ctx_wrapper(simgrid::kernel::context::SwappedContext* context)
43 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
44 __sanitizer_finish_switch_fiber(nullptr, &context->asan_ctx_->asan_stack_, &context->asan_ctx_->asan_stack_size_);
48 context->Context::stop();
49 } catch (simgrid::ForcefulKillException const&) {
50 XBT_DEBUG("Caught a ForcefulKillException");
51 } catch (simgrid::Exception const& e) {
52 XBT_INFO("Actor killed by an uncaught exception %s", simgrid::xbt::demangle(typeid(e).name()).get());
55 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
56 context->asan_stop_ = true;
66 /* thread-specific storage for the worker's context */
67 thread_local SwappedContext* SwappedContext::worker_context_ = nullptr;
69 SwappedContext::SwappedContext(std::function<void()>&& code, smx_actor_t actor, SwappedContextFactory* factory)
70 : Context(std::move(code), actor), factory_(*factory)
72 // Save maestro (=first created context) in preparation for run_all
73 if (not SIMIX_context_is_parallel() && factory_.maestro_context_ == nullptr)
74 factory_.maestro_context_ = this;
77 xbt_assert((actor->get_stacksize() & 0xf) == 0, "Actor stack size should be multiple of 16");
78 if (smx_context_guard_size > 0 && not MC_is_active()) {
79 #if PTH_STACKGROWTH != -1
81 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
83 "Please disable stack guards with --cfg=contexts:guard-size:0");
84 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
85 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
88 size_t size = actor->get_stacksize() + smx_context_guard_size;
90 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
91 * pointer returned by xbt_malloc0. */
92 unsigned char* alloc = static_cast<unsigned char*>(xbt_malloc0(size + xbt_pagesize));
93 stack_ = alloc - (reinterpret_cast<uintptr_t>(alloc) & (xbt_pagesize - 1)) + xbt_pagesize;
94 reinterpret_cast<unsigned char**>(stack_)[-1] = alloc;
95 #elif !defined(_WIN32)
97 if (posix_memalign(&alloc, xbt_pagesize, size) != 0)
98 xbt_die("Failed to allocate stack.");
99 this->stack_ = static_cast<unsigned char*>(alloc);
101 this->stack_ = static_cast<unsigned char*>(_aligned_malloc(size, xbt_pagesize));
105 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
107 "Failed to protect stack: %s.\n"
108 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
109 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
111 "https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization for more "
114 /* This is fatal. We are going to fail at some point when we try reusing this. */
117 this->stack_ = this->stack_ + smx_context_guard_size;
119 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(actor->get_stacksize()));
123 if (RUNNING_ON_VALGRIND)
124 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + actor->get_stacksize());
126 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
127 this->asan_stack_ = get_stack_bottom();
129 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
130 this->tsan_fiber_ = __tsan_create_fiber(0);
133 // not has_code(): in maestro context
134 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
135 this->tsan_fiber_ = __tsan_get_current_fiber();
140 SwappedContext::~SwappedContext()
142 if (stack_ == nullptr) // maestro has no extra stack
145 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
146 __tsan_destroy_fiber(tsan_fiber_);
149 if (RUNNING_ON_VALGRIND)
150 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
154 if (smx_context_guard_size > 0 && not MC_is_active()) {
155 stack_ = stack_ - smx_context_guard_size;
156 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
157 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
158 /* try to pursue anyway */
161 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
162 stack_ = reinterpret_cast<unsigned char**>(stack_)[-1];
165 #endif /* not windows */
170 unsigned char* SwappedContext::get_stack_bottom() const
172 // Depending on the stack direction, its bottom (that make_fcontext needs) may be the lower or higher end
173 #if PTH_STACKGROWTH == 1
176 return stack_ + get_actor()->get_stacksize();
180 void SwappedContext::stop()
183 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
184 throw ForcefulKillException();
187 void SwappedContext::swap_into(SwappedContext* to)
189 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
190 void* fake_stack = nullptr;
191 to->asan_ctx_ = this;
192 __sanitizer_start_switch_fiber(this->asan_stop_ ? nullptr : &fake_stack, to->asan_stack_, to->asan_stack_size_);
194 #if HAVE_SANITIZER_THREAD_FIBER_SUPPORT
195 __tsan_switch_to_fiber(to->tsan_fiber_, 0);
198 swap_into_for_real(to);
200 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
201 __sanitizer_finish_switch_fiber(fake_stack, &this->asan_ctx_->asan_stack_, &this->asan_ctx_->asan_stack_size_);
205 /** Maestro wants to run all ready actors */
206 void SwappedContextFactory::run_all()
208 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
209 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
210 * for the ones of the simulated processes that must run.
212 if (SIMIX_context_is_parallel()) {
213 // We lazily create the parmap so that all options are actually processed when doing so.
214 if (parmap_ == nullptr)
216 new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode()));
218 // Usually, Parmap::apply() executes the provided function on all elements of the array.
219 // Here, the executed function does not return the control to the parmap before all the array is processed:
220 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
221 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
222 // It only yields back to worker_context when the work array is exhausted.
223 // - So, resume() is only launched from the parmap for the first job of each minion.
225 [](const actor::ActorImpl* process) {
226 SwappedContext* context = static_cast<SwappedContext*>(process->context_.get());
229 simix_global->actors_to_run);
230 } else { // sequential execution
231 if (simix_global->actors_to_run.empty())
234 /* maestro is already saved in the first slot of workers_context_ */
235 const actor::ActorImpl* first_actor = simix_global->actors_to_run.front();
237 /* execute the first actor; it will chain to the others when using suspend() */
238 static_cast<SwappedContext*>(first_actor->context_.get())->resume();
242 /** Maestro wants to yield back to a given actor, so awake it on the current thread
244 * In parallel, it is only applied to the N first elements of the parmap array,
245 * where N is the amount of worker threads in the parmap.
246 * See SwappedContextFactory::run_all for details.
248 void SwappedContext::resume()
250 SwappedContext* old = static_cast<SwappedContext*>(self());
251 if (SIMIX_context_is_parallel()) {
252 // Save my current soul (either maestro, or one of the minions) in a thread-specific area
253 worker_context_ = old;
255 // Switch my soul and the actor's one
256 Context::set_current(this);
257 old->swap_into(this);
258 // No body runs that soul anymore at this point, but it is stored in a safe place.
259 // When the executed actor will do a blocking action, ActorImpl::yield() will call suspend(), below.
262 /** The actor wants to yield back to maestro, because it is blocked in a simcall (i.e., in ActorImpl::yield())
264 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
266 * This makes the parmap::apply awkward (see SwappedContextFactory::run_all()) because it only apply regularly
267 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
268 * and directly forth to the next executable actor.
270 void SwappedContext::suspend()
272 SwappedContext* next_context;
273 if (SIMIX_context_is_parallel()) {
274 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
275 boost::optional<smx_actor_t> next_work = factory_.parmap_->next();
277 // There is a next soul to embody (ie, another executable actor)
278 XBT_DEBUG("Run next process");
279 next_context = static_cast<SwappedContext*>(next_work.get()->context_.get());
281 // All actors were run, go back to the parmap context
282 XBT_DEBUG("No more actors to run");
283 // worker_context_ is my own soul, stored in thread_local when starting the scheduling round
284 next_context = worker_context_;
285 // When given that soul, the body will wait for the next scheduling round
287 } else { // sequential execution
288 /* determine the next context */
289 unsigned long int i = factory_.process_index_;
290 factory_.process_index_++;
292 if (i < simix_global->actors_to_run.size()) {
293 /* Actually swap into the next actor directly without transiting to maestro */
294 XBT_DEBUG("Run next actor");
295 next_context = static_cast<SwappedContext*>(simix_global->actors_to_run[i]->context_.get());
297 /* all processes were run, actually return to maestro */
298 XBT_DEBUG("No more actors to run");
299 next_context = factory_.maestro_context_;
302 Context::set_current(next_context);
303 this->swap_into(next_context);
306 } // namespace context
307 } // namespace kernel
308 } // namespace simgrid