+/* Copyright (c) 2009-2015. The SimGrid Team.
+ * All rights reserved. */
+
+/* This program is free software; you can redistribute it and/or modify it
+ * under the terms of the license (GNU LGPL) which comes with this package. */
+
+/* \file UContext.cpp Context switching with ucontexts from System V */
+
+#include <stdarg.h>
+
+#include "xbt/parmap.h"
+#include "smx_private.h"
+#include "smx_private.hpp"
+#include "src/internal_config.h"
+#include "src/context_sysv_config.h" /* loads context system definitions */
+#include "mc/mc.h"
+
+#ifdef _XBT_WIN32
+# include <xbt/win32_ucontext.h> /* context relative declarations */
+#else
+# include <ucontext.h> /* context relative declarations */
+#endif
+
+/** Many integers are needed to store a pointer
+ *
+ * This is a bit paranoid about sizeof(smx_ctx_sysv_t) not being a multiple
+ * of sizeof(int), but it doesn't harm. */
+#define CTX_ADDR_LEN \
+ (sizeof(void*) / sizeof(int) + \
+ !!(sizeof(void*) % sizeof(int)))
+
+/** A better makecontext
+ *
+ * Makecontext expects integer arguments, we the context
+ * variable is decomposed into a serie of integers and
+ * each integer is passed as argument to makecontext. */
+XBT_PRIVATE
+void simgrid_makecontext(ucontext* ucp, void (*func)(int first, ...), void* arg)
+{
+ int ctx_addr[CTX_ADDR_LEN];
+ memcpy(ctx_addr, &arg, sizeof(void*));
+ switch (CTX_ADDR_LEN) {
+ case 1:
+ makecontext(ucp, (void (*)())func, 1, ctx_addr[0]);
+ break;
+ case 2:
+ makecontext(ucp, (void (*)()) func, 2, ctx_addr[0], ctx_addr[1]);
+ break;
+ default:
+ xbt_die("Ucontexts are not supported on this arch yet (addr len = %zu/%zu = %zu)",
+ sizeof(void*), sizeof(int), CTX_ADDR_LEN);
+ }
+}
+
+XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
+
+namespace simgrid {
+namespace simix {
+ class UContext;
+ class SerialUContext;
+ class ParallelUContext;
+ class UContextFactory;
+}
+}
+
+#ifdef CONTEXT_THREADS
+static xbt_parmap_t sysv_parmap;
+static simgrid::simix::ParallelUContext** sysv_workers_context; /* space to save the worker's context in each thread */
+static unsigned long sysv_threads_working; /* number of threads that have started their work */
+static xbt_os_thread_key_t sysv_worker_id_key; /* thread-specific storage for the thread id */
+#endif
+static unsigned long sysv_process_index = 0; /* index of the next process to run in the
+ * list of runnable processes */
+static simgrid::simix::UContext* sysv_maestro_context;
+static bool sysv_parallel;
+
+namespace simgrid {
+namespace simix {
+
+class UContext : public Context {
+protected:
+ ucontext_t uc_; /* the ucontext that executes the code */
+ char *stack_ = nullptr; /* the thread stack */
+public:
+ friend UContextFactory;
+ UContext(xbt_main_func_t code,
+ int argc, char **argv,
+ void_pfn_smxprocess_t cleanup_func,
+ smx_process_t process);
+ ~UContext();
+protected:
+ static void wrapper(int first, ...);
+};
+
+class SerialUContext : public UContext {
+public:
+ SerialUContext(xbt_main_func_t code,
+ int argc, char **argv,
+ void_pfn_smxprocess_t cleanup_func,
+ smx_process_t process)
+ : UContext(code, argc, argv, cleanup_func, process)
+ {}
+ void stop() override;
+ void suspend() override;
+ void resume();
+};
+
+class ParallelUContext : public UContext {
+public:
+ ParallelUContext(xbt_main_func_t code,
+ int argc, char **argv,
+ void_pfn_smxprocess_t cleanup_func,
+ smx_process_t process)
+ : UContext(code, argc, argv, cleanup_func, process)
+ {}
+ void stop() override;
+ void suspend() override;
+ void resume();
+};
+
+class UContextFactory : public ContextFactory {
+public:
+ friend UContext;
+ friend SerialUContext;
+ friend ParallelUContext;
+
+ UContextFactory();
+ virtual ~UContextFactory();
+ virtual Context* create_context(
+ xbt_main_func_t, int, char **, void_pfn_smxprocess_t,
+ smx_process_t process
+ ) override;
+ void run_all() override;
+};
+
+XBT_PRIVATE ContextFactory* sysv_factory()
+{
+ XBT_VERB("Activating SYSV context factory");
+ return new UContextFactory();
+}
+
+UContextFactory::UContextFactory() : ContextFactory("UContextFactory")
+{
+ if (SIMIX_context_is_parallel()) {
+ sysv_parallel = true;
+#ifdef CONTEXT_THREADS /* To use parallel ucontexts a thread pool is needed */
+ int nthreads = SIMIX_context_get_nthreads();
+ sysv_parmap = nullptr;
+ sysv_workers_context = xbt_new(ParallelUContext*, nthreads);
+ sysv_maestro_context = nullptr;
+ xbt_os_thread_key_create(&sysv_worker_id_key);
+#else
+ THROWF(arg_error, 0, "No thread support for parallel context execution");
+#endif
+ } else {
+ sysv_parallel = false;
+ }
+}
+
+UContextFactory::~UContextFactory()
+{
+#ifdef CONTEXT_THREADS
+ if (sysv_parmap)
+ xbt_parmap_destroy(sysv_parmap);
+ xbt_free(sysv_workers_context);
+#endif
+}
+
+/* This function is called by maestro at the beginning of a scheduling round to get all working threads executing some stuff
+ * It is much easier to understand what happens if you see the working threads as bodies that swap their soul for the
+ * ones of the simulated processes that must run.
+ */
+void UContextFactory::run_all()
+{
+ if (sysv_parallel) {
+ #ifdef CONTEXT_THREADS
+ sysv_threads_working = 0;
+ // Parmap_apply ensures that every working thread get an index in the
+ // process_to_run array (through an atomic fetch_and_add),
+ // and runs the smx_ctx_sysv_resume_parallel function on that index
+
+ // We lazily create the parmap because the parmap creates context
+ // with simix_global->context_factory (which might not be initialized
+ // when bootstrapping):
+ if (sysv_parmap == nullptr)
+ sysv_parmap = xbt_parmap_new(
+ SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
+
+ xbt_parmap_apply(sysv_parmap,
+ [](void* arg) {
+ smx_process_t process = (smx_process_t) arg;
+ ParallelUContext* context = static_cast<ParallelUContext*>(process->context);
+ context->resume();
+ },
+ simix_global->process_to_run);
+ #else
+ xbt_die("You asked for a parallel execution, but you don't have any threads.");
+ #endif
+ } else {
+ // Serial:
+ smx_process_t first_process =
+ xbt_dynar_get_as(simix_global->process_to_run, 0, smx_process_t);
+ sysv_process_index = 1;
+ SerialUContext* context =
+ static_cast<SerialUContext*>(first_process->context);
+ context->resume();
+ }
+}
+
+Context* UContextFactory::create_context(
+ xbt_main_func_t code, int argc, char ** argv,
+ void_pfn_smxprocess_t cleanup,
+ smx_process_t process
+ )
+{
+ if (sysv_parallel)
+ return new_context<ParallelUContext>(code, argc, argv, cleanup, process);
+ else
+ return new_context<SerialUContext>(code, argc, argv, cleanup, process);
+}
+
+UContext::UContext(xbt_main_func_t code,
+ int argc, char **argv,
+ void_pfn_smxprocess_t cleanup_func,
+ smx_process_t process)
+ : Context(code, argc, argv, cleanup_func, process)
+{
+ /* if the user provided a function for the process then use it,
+ otherwise it is the context for maestro */
+ if (code) {
+ this->stack_ = (char*) SIMIX_context_stack_new();
+ getcontext(&this->uc_);
+ this->uc_.uc_link = nullptr;
+ this->uc_.uc_stack.ss_sp = pth_skaddr_makecontext(
+ this->stack_, smx_context_usable_stack_size);
+ this->uc_.uc_stack.ss_size = pth_sksize_makecontext(
+ this->stack_, smx_context_usable_stack_size);
+ simgrid_makecontext(&this->uc_, UContext::wrapper, this);
+ } else {
+ if (process != NULL && sysv_maestro_context == NULL)
+ sysv_maestro_context = this;
+ }
+
+#ifdef HAVE_MC
+ if (MC_is_active() && code) {
+ MC_register_stack_area(this->stack_, context->process,
+ &(this->uc_), smx_context_usable_stack_size);
+ }
+#endif
+}
+
+UContext::~UContext()
+{
+ SIMIX_context_stack_delete(this->stack_);
+}
+
+void UContext::wrapper(int first, ...)
+{
+ // Rebuild the Context* pointer from the integers:
+ int ctx_addr[CTX_ADDR_LEN];
+ UContext* context;
+ ctx_addr[0] = first;
+ if (CTX_ADDR_LEN > 1) {
+ va_list ap;
+ va_start(ap, first);
+ for (unsigned i = 1; i < CTX_ADDR_LEN; i++)
+ ctx_addr[i] = va_arg(ap, int);
+ va_end(ap);
+ }
+ memcpy(&context, ctx_addr, sizeof(UContext*));
+
+ (*context)();
+ context->stop();
+}
+
+void SerialUContext::stop()
+{
+ Context::stop();
+ this->suspend();
+}
+
+void SerialUContext::suspend()
+{
+ /* determine the next context */
+ SerialUContext* next_context = nullptr;
+ unsigned long int i = sysv_process_index++;
+
+ if (i < xbt_dynar_length(simix_global->process_to_run)) {
+ /* execute the next process */
+ XBT_DEBUG("Run next process");
+ next_context = (SerialUContext*) xbt_dynar_get_as(
+ simix_global->process_to_run,i, smx_process_t)->context;
+ }
+ else {
+ /* all processes were run, return to maestro */
+ XBT_DEBUG("No more process to run");
+ next_context = (SerialUContext*) sysv_maestro_context;
+ }
+ SIMIX_context_set_current(next_context);
+ swapcontext(&this->uc_, &next_context->uc_);
+}
+
+// UContextSerial
+
+void SerialUContext::resume()
+{
+ SIMIX_context_set_current(this);
+ swapcontext(&((SerialUContext*)sysv_maestro_context)->uc_, &this->uc_);
+}
+
+void ParallelUContext::stop()
+{
+ UContext::stop();
+ this->suspend();
+}
+
+/** Run one particular simulated process on the current thread. */
+void ParallelUContext::resume()
+{
+#ifdef CONTEXT_THREADS
+ // What is my containing body?
+ unsigned long worker_id = __sync_fetch_and_add(&sysv_threads_working, 1);
+ // Store the number of my containing body in os-thread-specific area :
+ xbt_os_thread_set_specific(sysv_worker_id_key, (void*) worker_id);
+ // Get my current soul:
+ ParallelUContext* worker_context = (ParallelUContext*) SIMIX_context_self();
+ // Write down that this soul is hosted in that body (for now)
+ sysv_workers_context[worker_id] = worker_context;
+ // Retrieve the system-level info that fuels this soul:
+ ucontext_t* worker_stack = &((ParallelUContext*) worker_context)->uc_;
+ // Write in simix that I switched my soul
+ SIMIX_context_set_current(this);
+ // Actually do that using the relevant library call:
+ swapcontext(worker_stack, &this->uc_);
+ // No body runs that soul anymore at this point.
+ // Instead the current body took the soul of simulated process
+ // The simulated process wakes back after the call to
+ // "SIMIX_context_suspend(self->context);" within
+ // smx_process.c::SIMIX_process_yield()
+
+ // From now on, the simulated processes will change their
+ // soul with the next soul to execute (in suspend_parallel, below).
+ // When nobody is to be executed in this scheduling round,
+ // the last simulated process will take back the initial
+ // soul of the current working thread
+#endif
+}
+
+/** Yield
+ *
+ * This function is called when a simulated process wants to yield back
+ * to the maestro in a blocking simcall. This naturally occurs within
+ * SIMIX_context_suspend(self->context), called from SIMIX_process_yield()
+ * Actually, it does not really yield back to maestro, but into the next
+ * process that must be executed. If no one is to be executed, then it
+ * yields to the initial soul that was in this working thread (that was
+ * saved in resume_parallel).
+ */
+void ParallelUContext::suspend()
+{
+#ifdef CONTEXT_THREADS
+ /* determine the next context */
+ // Get the next soul to embody now:
+ smx_process_t next_work = (smx_process_t) xbt_parmap_next(sysv_parmap);
+ ParallelUContext* next_context = nullptr;
+ // Will contain the next soul to run, either simulated or initial minion's one
+ ucontext_t* next_stack;
+
+ if (next_work != NULL) {
+ // There is a next soul to embody (ie, a next process to resume)
+ XBT_DEBUG("Run next process");
+ next_context = (ParallelUContext*) next_work->context;
+ }
+ else {
+ // All processes were run, go to the barrier
+ XBT_DEBUG("No more processes to run");
+ // Get back the identity of my body that was stored when starting
+ // the scheduling round
+ unsigned long worker_id =
+ (unsigned long) xbt_os_thread_get_specific(sysv_worker_id_key);
+ // Deduce the initial soul of that body
+ next_context = (ParallelUContext*) sysv_workers_context[worker_id];
+ // When given that soul, the body will wait for the next scheduling round
+ }
+
+ next_stack = &next_context->uc_;
+
+ SIMIX_context_set_current(next_context);
+ // Get that next soul:
+ swapcontext(&this->uc_, next_stack);
+#endif
+}
+
+}
+}
+
