1 /* Copyright (c) 2009-2015. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 /* \file UContext.cpp Context switching with ucontexts from System V */
13 #include "xbt/parmap.h"
14 #include "src/simix/smx_private.h"
15 #include "src/simix/smx_private.hpp"
16 #include "src/internal_config.h"
17 #include "src/context_sysv_config.h" /* loads context system definitions */
21 # include <xbt/win32_ucontext.h> /* context relative declarations */
23 # include <ucontext.h> /* context relative declarations */
26 /** Many integers are needed to store a pointer
28 * This is a bit paranoid about sizeof(smx_ctx_sysv_t) not being a multiple
29 * of sizeof(int), but it doesn't harm. */
30 #define CTX_ADDR_LEN \
31 (sizeof(void*) / sizeof(int) + \
32 !!(sizeof(void*) % sizeof(int)))
34 /** A better makecontext
36 * Makecontext expects integer arguments, we the context
37 * variable is decomposed into a serie of integers and
38 * each integer is passed as argument to makecontext. */
40 void simgrid_makecontext(ucontext_t* ucp, void (*func)(int first, ...), void* arg)
42 int ctx_addr[CTX_ADDR_LEN];
43 memcpy(ctx_addr, &arg, sizeof(void*));
44 switch (CTX_ADDR_LEN) {
46 makecontext(ucp, (void (*)())func, 1, ctx_addr[0]);
49 makecontext(ucp, (void (*)()) func, 2, ctx_addr[0], ctx_addr[1]);
52 xbt_die("Ucontexts are not supported on this arch yet (addr len = %zu/%zu = %zu)",
53 sizeof(void*), sizeof(int), CTX_ADDR_LEN);
57 XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
63 class ParallelUContext;
64 class UContextFactory;
68 #ifdef HAVE_THREAD_CONTEXTS
69 static xbt_parmap_t sysv_parmap;
70 static simgrid::simix::ParallelUContext** sysv_workers_context; /* space to save the worker's context in each thread */
71 static unsigned long sysv_threads_working; /* number of threads that have started their work */
72 static xbt_os_thread_key_t sysv_worker_id_key; /* thread-specific storage for the thread id */
74 static unsigned long sysv_process_index = 0; /* index of the next process to run in the
75 * list of runnable processes */
76 static simgrid::simix::UContext* sysv_maestro_context;
77 static bool sysv_parallel;
79 // The name of this function is currently hardcoded in the code (as string).
80 // Do not change it without fixing those references as well.
81 static void smx_ctx_sysv_wrapper(int first, ...);
86 class UContext : public Context {
88 ucontext_t uc_; /* the ucontext that executes the code */
89 char *stack_ = nullptr; /* the thread stack */
91 friend UContextFactory;
92 UContext(std::function<void()> code,
93 void_pfn_smxprocess_t cleanup_func, smx_process_t process);
97 class SerialUContext : public UContext {
99 SerialUContext(std::function<void()> code,
100 void_pfn_smxprocess_t cleanup_func, smx_process_t process)
101 : UContext(std::move(code), cleanup_func, process)
103 void stop() override;
104 void suspend() override;
108 class ParallelUContext : public UContext {
110 ParallelUContext(std::function<void()> code,
111 void_pfn_smxprocess_t cleanup_func, smx_process_t process)
112 : UContext(std::move(code), cleanup_func, process)
114 void stop() override;
115 void suspend() override;
119 class UContextFactory : public ContextFactory {
122 friend SerialUContext;
123 friend ParallelUContext;
126 virtual ~UContextFactory();
127 virtual Context* create_context(std::function<void()> code,
128 void_pfn_smxprocess_t, smx_process_t process) override;
129 void run_all() override;
132 XBT_PRIVATE ContextFactory* sysv_factory()
134 XBT_VERB("Activating SYSV context factory");
135 return new UContextFactory();
138 UContextFactory::UContextFactory() : ContextFactory("UContextFactory")
140 if (SIMIX_context_is_parallel()) {
141 sysv_parallel = true;
142 #ifdef HAVE_THREAD_CONTEXTS /* To use parallel ucontexts a thread pool is needed */
143 int nthreads = SIMIX_context_get_nthreads();
144 sysv_parmap = nullptr;
145 sysv_workers_context = xbt_new(ParallelUContext*, nthreads);
146 sysv_maestro_context = nullptr;
147 xbt_os_thread_key_create(&sysv_worker_id_key);
149 THROWF(arg_error, 0, "No thread support for parallel context execution");
152 sysv_parallel = false;
156 UContextFactory::~UContextFactory()
158 #ifdef HAVE_THREAD_CONTEXTS
160 xbt_parmap_destroy(sysv_parmap);
161 xbt_free(sysv_workers_context);
165 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some stuff
166 * It is much easier to understand what happens if you see the working threads as bodies that swap their soul for the
167 * ones of the simulated processes that must run.
169 void UContextFactory::run_all()
172 #ifdef HAVE_THREAD_CONTEXTS
173 sysv_threads_working = 0;
174 // Parmap_apply ensures that every working thread get an index in the
175 // process_to_run array (through an atomic fetch_and_add),
176 // and runs the smx_ctx_sysv_resume_parallel function on that index
178 // We lazily create the parmap because the parmap creates context
179 // with simix_global->context_factory (which might not be initialized
180 // when bootstrapping):
181 if (sysv_parmap == nullptr)
182 sysv_parmap = xbt_parmap_new(
183 SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
185 xbt_parmap_apply(sysv_parmap,
187 smx_process_t process = (smx_process_t) arg;
188 ParallelUContext* context = static_cast<ParallelUContext*>(process->context);
191 simix_global->process_to_run);
193 xbt_die("You asked for a parallel execution, but you don't have any threads.");
197 smx_process_t first_process =
198 xbt_dynar_get_as(simix_global->process_to_run, 0, smx_process_t);
199 sysv_process_index = 1;
200 SerialUContext* context =
201 static_cast<SerialUContext*>(first_process->context);
206 Context* UContextFactory::create_context(std::function<void()> code,
207 void_pfn_smxprocess_t cleanup, smx_process_t process)
210 return new_context<ParallelUContext>(std::move(code), cleanup, process);
212 return new_context<SerialUContext>(std::move(code), cleanup, process);
215 UContext::UContext(std::function<void()> code,
216 void_pfn_smxprocess_t cleanup_func, smx_process_t process)
217 : Context(std::move(code), cleanup_func, process)
219 /* if the user provided a function for the process then use it,
220 otherwise it is the context for maestro */
222 this->stack_ = (char*) SIMIX_context_stack_new();
223 getcontext(&this->uc_);
224 this->uc_.uc_link = nullptr;
225 this->uc_.uc_stack.ss_sp = pth_skaddr_makecontext(
226 this->stack_, smx_context_usable_stack_size);
227 this->uc_.uc_stack.ss_size = pth_sksize_makecontext(
228 this->stack_, smx_context_usable_stack_size);
229 simgrid_makecontext(&this->uc_, smx_ctx_sysv_wrapper, this);
231 if (process != NULL && sysv_maestro_context == NULL)
232 sysv_maestro_context = this;
236 if (MC_is_active() && code) {
237 MC_register_stack_area(this->stack_, process,
238 &(this->uc_), smx_context_usable_stack_size);
243 UContext::~UContext()
245 SIMIX_context_stack_delete(this->stack_);
251 static void smx_ctx_sysv_wrapper(int first, ...)
253 // Rebuild the Context* pointer from the integers:
254 int ctx_addr[CTX_ADDR_LEN];
255 simgrid::simix::UContext* context;
257 if (CTX_ADDR_LEN > 1) {
260 for (unsigned i = 1; i < CTX_ADDR_LEN; i++)
261 ctx_addr[i] = va_arg(ap, int);
264 memcpy(&context, ctx_addr, sizeof(simgrid::simix::UContext*));
273 void SerialUContext::stop()
279 void SerialUContext::suspend()
281 /* determine the next context */
282 SerialUContext* next_context = nullptr;
283 unsigned long int i = sysv_process_index++;
285 if (i < xbt_dynar_length(simix_global->process_to_run)) {
286 /* execute the next process */
287 XBT_DEBUG("Run next process");
288 next_context = (SerialUContext*) xbt_dynar_get_as(
289 simix_global->process_to_run,i, smx_process_t)->context;
292 /* all processes were run, return to maestro */
293 XBT_DEBUG("No more process to run");
294 next_context = (SerialUContext*) sysv_maestro_context;
296 SIMIX_context_set_current(next_context);
297 swapcontext(&this->uc_, &next_context->uc_);
302 void SerialUContext::resume()
304 SIMIX_context_set_current(this);
305 swapcontext(&((SerialUContext*)sysv_maestro_context)->uc_, &this->uc_);
308 void ParallelUContext::stop()
314 /** Run one particular simulated process on the current thread. */
315 void ParallelUContext::resume()
317 #ifdef HAVE_THREAD_CONTEXTS
318 // What is my containing body?
319 unsigned long worker_id = __sync_fetch_and_add(&sysv_threads_working, 1);
320 // Store the number of my containing body in os-thread-specific area :
321 xbt_os_thread_set_specific(sysv_worker_id_key, (void*) worker_id);
322 // Get my current soul:
323 ParallelUContext* worker_context = (ParallelUContext*) SIMIX_context_self();
324 // Write down that this soul is hosted in that body (for now)
325 sysv_workers_context[worker_id] = worker_context;
326 // Retrieve the system-level info that fuels this soul:
327 ucontext_t* worker_stack = &((ParallelUContext*) worker_context)->uc_;
328 // Write in simix that I switched my soul
329 SIMIX_context_set_current(this);
330 // Actually do that using the relevant library call:
331 swapcontext(worker_stack, &this->uc_);
332 // No body runs that soul anymore at this point.
333 // Instead the current body took the soul of simulated process
334 // The simulated process wakes back after the call to
335 // "SIMIX_context_suspend(self->context);" within
336 // smx_process.c::SIMIX_process_yield()
338 // From now on, the simulated processes will change their
339 // soul with the next soul to execute (in suspend_parallel, below).
340 // When nobody is to be executed in this scheduling round,
341 // the last simulated process will take back the initial
342 // soul of the current working thread
348 * This function is called when a simulated process wants to yield back
349 * to the maestro in a blocking simcall. This naturally occurs within
350 * SIMIX_context_suspend(self->context), called from SIMIX_process_yield()
351 * Actually, it does not really yield back to maestro, but into the next
352 * process that must be executed. If no one is to be executed, then it
353 * yields to the initial soul that was in this working thread (that was
354 * saved in resume_parallel).
356 void ParallelUContext::suspend()
358 #ifdef HAVE_THREAD_CONTEXTS
359 /* determine the next context */
360 // Get the next soul to embody now:
361 smx_process_t next_work = (smx_process_t) xbt_parmap_next(sysv_parmap);
362 ParallelUContext* next_context = nullptr;
363 // Will contain the next soul to run, either simulated or initial minion's one
364 ucontext_t* next_stack;
366 if (next_work != NULL) {
367 // There is a next soul to embody (ie, a next process to resume)
368 XBT_DEBUG("Run next process");
369 next_context = (ParallelUContext*) next_work->context;
372 // All processes were run, go to the barrier
373 XBT_DEBUG("No more processes to run");
374 // Get back the identity of my body that was stored when starting
375 // the scheduling round
376 unsigned long worker_id =
377 (unsigned long) xbt_os_thread_get_specific(sysv_worker_id_key);
378 // Deduce the initial soul of that body
379 next_context = (ParallelUContext*) sysv_workers_context[worker_id];
380 // When given that soul, the body will wait for the next scheduling round
383 next_stack = &next_context->uc_;
385 SIMIX_context_set_current(next_context);
386 // Get that next soul:
387 swapcontext(&this->uc_, next_stack);