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 CONTEXT_THREADS
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;
82 class UContext : public Context {
84 ucontext_t uc_; /* the ucontext that executes the code */
85 char *stack_ = nullptr; /* the thread stack */
87 friend UContextFactory;
88 UContext(std::function<void()> code,
89 void_pfn_smxprocess_t cleanup_func, smx_process_t process);
92 static void wrapper(int first, ...);
95 class SerialUContext : public UContext {
97 SerialUContext(std::function<void()> code,
98 void_pfn_smxprocess_t cleanup_func, smx_process_t process)
99 : UContext(std::move(code), cleanup_func, process)
101 void stop() override;
102 void suspend() override;
106 class ParallelUContext : public UContext {
108 ParallelUContext(std::function<void()> code,
109 void_pfn_smxprocess_t cleanup_func, smx_process_t process)
110 : UContext(std::move(code), cleanup_func, process)
112 void stop() override;
113 void suspend() override;
117 class UContextFactory : public ContextFactory {
120 friend SerialUContext;
121 friend ParallelUContext;
124 virtual ~UContextFactory();
125 virtual Context* create_context(std::function<void()> code,
126 void_pfn_smxprocess_t, smx_process_t process) override;
127 void run_all() override;
130 XBT_PRIVATE ContextFactory* sysv_factory()
132 XBT_VERB("Activating SYSV context factory");
133 return new UContextFactory();
136 UContextFactory::UContextFactory() : ContextFactory("UContextFactory")
138 if (SIMIX_context_is_parallel()) {
139 sysv_parallel = true;
140 #ifdef CONTEXT_THREADS /* To use parallel ucontexts a thread pool is needed */
141 int nthreads = SIMIX_context_get_nthreads();
142 sysv_parmap = nullptr;
143 sysv_workers_context = xbt_new(ParallelUContext*, nthreads);
144 sysv_maestro_context = nullptr;
145 xbt_os_thread_key_create(&sysv_worker_id_key);
147 THROWF(arg_error, 0, "No thread support for parallel context execution");
150 sysv_parallel = false;
154 UContextFactory::~UContextFactory()
156 #ifdef CONTEXT_THREADS
158 xbt_parmap_destroy(sysv_parmap);
159 xbt_free(sysv_workers_context);
163 /* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some stuff
164 * It is much easier to understand what happens if you see the working threads as bodies that swap their soul for the
165 * ones of the simulated processes that must run.
167 void UContextFactory::run_all()
170 #ifdef CONTEXT_THREADS
171 sysv_threads_working = 0;
172 // Parmap_apply ensures that every working thread get an index in the
173 // process_to_run array (through an atomic fetch_and_add),
174 // and runs the smx_ctx_sysv_resume_parallel function on that index
176 // We lazily create the parmap because the parmap creates context
177 // with simix_global->context_factory (which might not be initialized
178 // when bootstrapping):
179 if (sysv_parmap == nullptr)
180 sysv_parmap = xbt_parmap_new(
181 SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
183 xbt_parmap_apply(sysv_parmap,
185 smx_process_t process = (smx_process_t) arg;
186 ParallelUContext* context = static_cast<ParallelUContext*>(process->context);
189 simix_global->process_to_run);
191 xbt_die("You asked for a parallel execution, but you don't have any threads.");
195 smx_process_t first_process =
196 xbt_dynar_get_as(simix_global->process_to_run, 0, smx_process_t);
197 sysv_process_index = 1;
198 SerialUContext* context =
199 static_cast<SerialUContext*>(first_process->context);
204 Context* UContextFactory::create_context(std::function<void()> code,
205 void_pfn_smxprocess_t cleanup, smx_process_t process)
208 return new_context<ParallelUContext>(std::move(code), cleanup, process);
210 return new_context<SerialUContext>(std::move(code), cleanup, process);
213 UContext::UContext(std::function<void()> code,
214 void_pfn_smxprocess_t cleanup_func, smx_process_t process)
215 : Context(std::move(code), cleanup_func, process)
217 /* if the user provided a function for the process then use it,
218 otherwise it is the context for maestro */
220 this->stack_ = (char*) SIMIX_context_stack_new();
221 getcontext(&this->uc_);
222 this->uc_.uc_link = nullptr;
223 this->uc_.uc_stack.ss_sp = pth_skaddr_makecontext(
224 this->stack_, smx_context_usable_stack_size);
225 this->uc_.uc_stack.ss_size = pth_sksize_makecontext(
226 this->stack_, smx_context_usable_stack_size);
227 simgrid_makecontext(&this->uc_, UContext::wrapper, this);
229 if (process != NULL && sysv_maestro_context == NULL)
230 sysv_maestro_context = this;
234 if (MC_is_active() && code) {
235 MC_register_stack_area(this->stack_, process,
236 &(this->uc_), smx_context_usable_stack_size);
241 UContext::~UContext()
243 SIMIX_context_stack_delete(this->stack_);
246 void UContext::wrapper(int first, ...)
248 // Rebuild the Context* pointer from the integers:
249 int ctx_addr[CTX_ADDR_LEN];
252 if (CTX_ADDR_LEN > 1) {
255 for (unsigned i = 1; i < CTX_ADDR_LEN; i++)
256 ctx_addr[i] = va_arg(ap, int);
259 memcpy(&context, ctx_addr, sizeof(UContext*));
265 void SerialUContext::stop()
271 void SerialUContext::suspend()
273 /* determine the next context */
274 SerialUContext* next_context = nullptr;
275 unsigned long int i = sysv_process_index++;
277 if (i < xbt_dynar_length(simix_global->process_to_run)) {
278 /* execute the next process */
279 XBT_DEBUG("Run next process");
280 next_context = (SerialUContext*) xbt_dynar_get_as(
281 simix_global->process_to_run,i, smx_process_t)->context;
284 /* all processes were run, return to maestro */
285 XBT_DEBUG("No more process to run");
286 next_context = (SerialUContext*) sysv_maestro_context;
288 SIMIX_context_set_current(next_context);
289 swapcontext(&this->uc_, &next_context->uc_);
294 void SerialUContext::resume()
296 SIMIX_context_set_current(this);
297 swapcontext(&((SerialUContext*)sysv_maestro_context)->uc_, &this->uc_);
300 void ParallelUContext::stop()
306 /** Run one particular simulated process on the current thread. */
307 void ParallelUContext::resume()
309 #ifdef CONTEXT_THREADS
310 // What is my containing body?
311 unsigned long worker_id = __sync_fetch_and_add(&sysv_threads_working, 1);
312 // Store the number of my containing body in os-thread-specific area :
313 xbt_os_thread_set_specific(sysv_worker_id_key, (void*) worker_id);
314 // Get my current soul:
315 ParallelUContext* worker_context = (ParallelUContext*) SIMIX_context_self();
316 // Write down that this soul is hosted in that body (for now)
317 sysv_workers_context[worker_id] = worker_context;
318 // Retrieve the system-level info that fuels this soul:
319 ucontext_t* worker_stack = &((ParallelUContext*) worker_context)->uc_;
320 // Write in simix that I switched my soul
321 SIMIX_context_set_current(this);
322 // Actually do that using the relevant library call:
323 swapcontext(worker_stack, &this->uc_);
324 // No body runs that soul anymore at this point.
325 // Instead the current body took the soul of simulated process
326 // The simulated process wakes back after the call to
327 // "SIMIX_context_suspend(self->context);" within
328 // smx_process.c::SIMIX_process_yield()
330 // From now on, the simulated processes will change their
331 // soul with the next soul to execute (in suspend_parallel, below).
332 // When nobody is to be executed in this scheduling round,
333 // the last simulated process will take back the initial
334 // soul of the current working thread
340 * This function is called when a simulated process wants to yield back
341 * to the maestro in a blocking simcall. This naturally occurs within
342 * SIMIX_context_suspend(self->context), called from SIMIX_process_yield()
343 * Actually, it does not really yield back to maestro, but into the next
344 * process that must be executed. If no one is to be executed, then it
345 * yields to the initial soul that was in this working thread (that was
346 * saved in resume_parallel).
348 void ParallelUContext::suspend()
350 #ifdef CONTEXT_THREADS
351 /* determine the next context */
352 // Get the next soul to embody now:
353 smx_process_t next_work = (smx_process_t) xbt_parmap_next(sysv_parmap);
354 ParallelUContext* next_context = nullptr;
355 // Will contain the next soul to run, either simulated or initial minion's one
356 ucontext_t* next_stack;
358 if (next_work != NULL) {
359 // There is a next soul to embody (ie, a next process to resume)
360 XBT_DEBUG("Run next process");
361 next_context = (ParallelUContext*) next_work->context;
364 // All processes were run, go to the barrier
365 XBT_DEBUG("No more processes to run");
366 // Get back the identity of my body that was stored when starting
367 // the scheduling round
368 unsigned long worker_id =
369 (unsigned long) xbt_os_thread_get_specific(sysv_worker_id_key);
370 // Deduce the initial soul of that body
371 next_context = (ParallelUContext*) sysv_workers_context[worker_id];
372 // When given that soul, the body will wait for the next scheduling round
375 next_stack = &next_context->uc_;
377 SIMIX_context_set_current(next_context);
378 // Get that next soul:
379 swapcontext(&this->uc_, next_stack);