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>
34 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
36 // The name of this function is currently hardcoded in MC (as string).
37 // Do not change it without fixing those references as well.
38 void smx_ctx_wrapper(simgrid::kernel::context::SwappedContext* context)
40 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
41 __sanitizer_finish_switch_fiber(nullptr, &context->asan_ctx_->asan_stack_, &context->asan_ctx_->asan_stack_size_);
45 context->Context::stop();
46 } catch (simgrid::ForcefulKillException const&) {
47 XBT_DEBUG("Caught a ForcefulKillException");
48 } catch (simgrid::Exception const& e) {
49 XBT_INFO("Actor killed by an uncaught exception %s", simgrid::xbt::demangle(typeid(e).name()).get());
52 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
53 context->asan_stop_ = true;
63 /* thread-specific storage for the worker's context */
64 thread_local SwappedContext* SwappedContext::worker_context_ = nullptr;
66 SwappedContext::SwappedContext(std::function<void()>&& code, smx_actor_t actor, SwappedContextFactory* factory)
67 : Context(std::move(code), actor), factory_(*factory)
69 // Save maestro (=context created first) in preparation for run_all
70 if (not SIMIX_context_is_parallel() && factory_.maestro_context_ == nullptr)
71 factory_.maestro_context_ = this;
74 xbt_assert((smx_context_stack_size & 0xf) == 0, "smx_context_stack_size should be multiple of 16");
75 if (smx_context_guard_size > 0 && not MC_is_active()) {
76 #if PTH_STACKGROWTH != -1
78 "Stack overflow protection is known to be broken on your system: you stacks grow upwards (or detection is "
80 "Please disable stack guards with --cfg=contexts:guard-size:0");
81 /* Current code for stack overflow protection assumes that stacks are growing downward (PTH_STACKGROWTH == -1).
82 * Protected pages need to be put after the stack when PTH_STACKGROWTH == 1. */
85 size_t size = smx_context_stack_size + smx_context_guard_size;
87 /* Cannot use posix_memalign when SIMGRID_HAVE_MC. Align stack by hand, and save the
88 * pointer returned by xbt_malloc0. */
89 unsigned char* alloc = static_cast<unsigned char*>(xbt_malloc0(size + xbt_pagesize));
90 stack_ = alloc - (reinterpret_cast<uintptr_t>(alloc) & (xbt_pagesize - 1)) + xbt_pagesize;
91 reinterpret_cast<unsigned char**>(stack_)[-1] = alloc;
92 #elif !defined(_WIN32)
94 if (posix_memalign(&alloc, xbt_pagesize, size) != 0)
95 xbt_die("Failed to allocate stack.");
96 this->stack_ = static_cast<unsigned char*>(alloc);
98 this->stack_ = static_cast<unsigned char*>(_aligned_malloc(size, xbt_pagesize));
102 if (mprotect(this->stack_, smx_context_guard_size, PROT_NONE) == -1) {
104 "Failed to protect stack: %s.\n"
105 "If you are running a lot of actors, you may be exceeding the amount of mappings allowed per process.\n"
106 "On Linux systems, change this value with sudo sysctl -w vm.max_map_count=newvalue (default value: 65536)\n"
108 "https://simgrid.org/doc/latest/Configuring_SimGrid.html#configuring-the-user-code-virtualization for more "
111 /* This is fatal. We are going to fail at some point when we try reusing this. */
114 this->stack_ = this->stack_ + smx_context_guard_size;
116 this->stack_ = static_cast<unsigned char*>(xbt_malloc0(smx_context_stack_size));
120 if (RUNNING_ON_VALGRIND)
121 this->valgrind_stack_id_ = VALGRIND_STACK_REGISTER(this->stack_, this->stack_ + smx_context_stack_size);
123 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
124 this->asan_stack_ = get_stack_bottom();
129 SwappedContext::~SwappedContext()
131 if (stack_ == nullptr) // maestro has no extra stack
135 if (RUNNING_ON_VALGRIND)
136 VALGRIND_STACK_DEREGISTER(valgrind_stack_id_);
140 if (smx_context_guard_size > 0 && not MC_is_active()) {
141 stack_ = stack_ - smx_context_guard_size;
142 if (mprotect(stack_, smx_context_guard_size, PROT_READ | PROT_WRITE) == -1) {
143 XBT_WARN("Failed to remove page protection: %s", strerror(errno));
144 /* try to pursue anyway */
147 /* Retrieve the saved pointer. See SIMIX_context_stack_new above. */
148 stack_ = reinterpret_cast<unsigned char**>(stack_)[-1];
151 #endif /* not windows */
156 void SwappedContext::stop()
159 /* We must cut the actor execution using an exception to properly free the C++ RAII variables */
160 throw ForcefulKillException();
163 void SwappedContext::swap_into(SwappedContext* to)
165 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
166 void* fake_stack = nullptr;
167 to->asan_ctx_ = this;
168 __sanitizer_start_switch_fiber(this->asan_stop_ ? nullptr : &fake_stack, to->asan_stack_, to->asan_stack_size_);
171 swap_into_for_real(to);
173 #if HAVE_SANITIZER_ADDRESS_FIBER_SUPPORT
174 __sanitizer_finish_switch_fiber(fake_stack, &this->asan_ctx_->asan_stack_, &this->asan_ctx_->asan_stack_size_);
178 /** Maestro wants to run all ready actors */
179 void SwappedContextFactory::run_all()
181 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some
182 * stuff It is much easier to understand what happens if you see the working threads as bodies that swap their soul
183 * for the ones of the simulated processes that must run.
185 if (SIMIX_context_is_parallel()) {
186 // We lazily create the parmap so that all options are actually processed when doing so.
187 if (parmap_ == nullptr)
189 new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode()));
191 // Usually, Parmap::apply() executes the provided function on all elements of the array.
192 // Here, the executed function does not return the control to the parmap before all the array is processed:
193 // - suspend() should switch back to the worker_context (either maestro or one of its minions) to return
194 // the control to the parmap. Instead, it uses parmap_->next() to steal another work, and does it directly.
195 // It only yields back to worker_context when the work array is exhausted.
196 // - So, resume() is only launched from the parmap for the first job of each minion.
198 [](const actor::ActorImpl* process) {
199 SwappedContext* context = static_cast<SwappedContext*>(process->context_.get());
202 simix_global->actors_to_run);
203 } else { // sequential execution
204 if (simix_global->actors_to_run.empty())
207 /* maestro is already saved in the first slot of workers_context_ */
208 const actor::ActorImpl* first_actor = simix_global->actors_to_run.front();
210 /* execute the first actor; it will chain to the others when using suspend() */
211 static_cast<SwappedContext*>(first_actor->context_.get())->resume();
215 /** Maestro wants to yield back to a given actor, so awake it on the current thread
217 * In parallel, it is only applied to the N first elements of the parmap array,
218 * where N is the amount of worker threads in the parmap.
219 * See SwappedContextFactory::run_all for details.
221 void SwappedContext::resume()
223 SwappedContext* old = static_cast<SwappedContext*>(self());
224 if (SIMIX_context_is_parallel()) {
225 // Save my current soul (either maestro, or one of the minions) in a thread-specific area
226 worker_context_ = old;
228 // Switch my soul and the actor's one
229 Context::set_current(this);
230 old->swap_into(this);
231 // No body runs that soul anymore at this point, but it is stored in a safe place.
232 // When the executed actor will do a blocking action, ActorImpl::yield() will call suspend(), below.
235 /** The actor wants to yield back to maestro, because it is blocked in a simcall (i.e., in ActorImpl::yield())
237 * Actually, it does not really yield back to maestro, but directly into the next executable actor.
239 * This makes the parmap::apply awkward (see SwappedContextFactory::run_all()) because it only apply regularly
240 * on the few first elements of the array, but it saves a lot of context switches back to maestro,
241 * and directly forth to the next executable actor.
243 void SwappedContext::suspend()
245 SwappedContext* next_context;
246 if (SIMIX_context_is_parallel()) {
247 // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
248 boost::optional<smx_actor_t> next_work = factory_.parmap_->next();
250 // There is a next soul to embody (ie, another executable actor)
251 XBT_DEBUG("Run next process");
252 next_context = static_cast<SwappedContext*>(next_work.get()->context_.get());
254 // All actors were run, go back to the parmap context
255 XBT_DEBUG("No more actors to run");
256 // worker_context_ is my own soul, stored in thread_local when starting the scheduling round
257 next_context = worker_context_;
258 // When given that soul, the body will wait for the next scheduling round
260 } else { // sequential execution
261 /* determine the next context */
262 unsigned long int i = factory_.process_index_;
263 factory_.process_index_++;
265 if (i < simix_global->actors_to_run.size()) {
266 /* Actually swap into the next actor directly without transiting to maestro */
267 XBT_DEBUG("Run next actor");
268 next_context = static_cast<SwappedContext*>(simix_global->actors_to_run[i]->context_.get());
270 /* all processes were run, actually return to maestro */
271 XBT_DEBUG("No more actors to run");
272 next_context = factory_.maestro_context_;
275 Context::set_current(next_context);
276 this->swap_into(next_context);
279 } // namespace context
280 } // namespace kernel
281 } // namespace simgrid