-/* Copyright (c) 2009-2017. The SimGrid Team. All rights reserved. */
+/* Copyright (c) 2009-2018. 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 <ucontext.h> /* context relative declarations */
+#include "context_private.hpp"
#include "mc/mc.h"
-#include "src/mc/mc_ignore.h"
+#include "simgrid/Exception.hpp"
+#include "src/mc/mc_ignore.hpp"
#include "src/simix/ActorImpl.hpp"
-#include "src/simix/smx_private.h"
-#include "xbt/parmap.hpp"
+#include "src/simix/smx_private.hpp"
-/** 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. */
-static void simgrid_makecontext(ucontext_t* 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);
- }
-}
+#include "ContextUnix.hpp"
XBT_LOG_EXTERNAL_DEFAULT_CATEGORY(simix_context);
-namespace simgrid {
-namespace kernel {
-namespace context {
- class UContext;
- class SerialUContext;
- class ParallelUContext;
- class UContextFactory;
-}}}
-
-#if HAVE_THREAD_CONTEXTS
-static simgrid::xbt::Parmap<smx_actor_t>* sysv_parmap;
-static simgrid::kernel::context::ParallelUContext** sysv_workers_context; /* space to save the worker's context in each thread */
-static uintptr_t 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::kernel::context::UContext* sysv_maestro_context;
-static bool sysv_parallel;
+/** Many integers are needed to store a pointer
+ *
+ * Support up to two ints. */
+constexpr int CTX_ADDR_LEN = 2;
-// The name of this function is currently hardcoded in the code (as string).
-// Do not change it without fixing those references as well.
-static void smx_ctx_sysv_wrapper(int first, ...);
+static_assert(sizeof(simgrid::kernel::context::UContext*) <= CTX_ADDR_LEN * sizeof(int),
+ "Ucontexts are not supported on this arch yet");
namespace simgrid {
namespace kernel {
namespace context {
-class UContext : public Context {
-protected:
- ucontext_t uc_; /* the ucontext that executes the code */
- char *stack_ = nullptr; /* the thread stack */
-public:
- friend UContextFactory;
- UContext(std::function<void()> code,
- void_pfn_smxprocess_t cleanup_func, smx_actor_t process);
- ~UContext() override;
-};
-
-class SerialUContext : public UContext {
-public:
- SerialUContext(std::function<void()> code,
- void_pfn_smxprocess_t cleanup_func, smx_actor_t process)
- : UContext(std::move(code), cleanup_func, process)
- {}
- void stop() override;
- void suspend() override;
- void resume();
-};
-
-class ParallelUContext : public UContext {
-public:
- ParallelUContext(std::function<void()> code,
- void_pfn_smxprocess_t cleanup_func, smx_actor_t process)
- : UContext(std::move(code), cleanup_func, process)
- {}
- void stop() override;
- void suspend() override;
- void resume();
-};
-
-class UContextFactory : public ContextFactory {
-public:
- friend UContext;
- friend SerialUContext;
- friend ParallelUContext;
-
- UContextFactory();
- ~UContextFactory() override;
- Context* create_context(std::function<void()> code,
- void_pfn_smxprocess_t cleanup, smx_actor_t process) override;
- void run_all() override;
-};
-
-XBT_PRIVATE ContextFactory* sysv_factory()
+// UContextFactory
+Context* UContextFactory::create_context(std::function<void()> code, void_pfn_smxprocess_t cleanup, smx_actor_t process)
{
- XBT_VERB("Activating SYSV context factory");
- return new UContextFactory();
-}
-
-UContextFactory::UContextFactory() : ContextFactory("UContextFactory")
-{
- if (SIMIX_context_is_parallel()) {
- sysv_parallel = true;
-#if HAVE_THREAD_CONTEXTS /* 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()
-{
-#if HAVE_THREAD_CONTEXTS
- delete sysv_parmap;
- xbt_free(sysv_workers_context);
-#endif
+ if (parallel_)
+ return new_context<ParallelUContext>(std::move(code), cleanup, process, this);
+ else
+ return new_context<UContext>(std::move(code), cleanup, process, this);
}
-/* 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) {
-#if HAVE_THREAD_CONTEXTS
- 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 =
- new simgrid::xbt::Parmap<smx_actor_t>(SIMIX_context_get_nthreads(), SIMIX_context_get_parallel_mode());
-
- sysv_parmap->apply(
- [](smx_actor_t process) {
- 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:
- if (simix_global->process_to_run.empty())
- return;
-
- smx_actor_t first_process = simix_global->process_to_run.front();
- sysv_process_index = 1;
- SerialUContext* context = static_cast<SerialUContext*>(first_process->context);
- context->resume();
- }
-}
-Context* UContextFactory::create_context(std::function<void()> code,
- void_pfn_smxprocess_t cleanup, smx_actor_t process)
-{
- if (sysv_parallel)
- return new_context<ParallelUContext>(std::move(code), cleanup, process);
- else
- return new_context<SerialUContext>(std::move(code), cleanup, process);
-}
+// UContext
-UContext::UContext(std::function<void()> code,
- void_pfn_smxprocess_t cleanup_func, smx_actor_t process)
- : Context(std::move(code), cleanup_func, process)
+UContext::UContext(std::function<void()> code, void_pfn_smxprocess_t cleanup_func, smx_actor_t process,
+ SwappedContextFactory* factory)
+ : SwappedContext(std::move(code), cleanup_func, process, factory)
{
/* if the user provided a function for the process then use it, otherwise it is the context for maestro */
if (has_code()) {
- this->stack_ = (char*) SIMIX_context_stack_new();
getcontext(&this->uc_);
this->uc_.uc_link = nullptr;
this->uc_.uc_stack.ss_sp = sg_makecontext_stack_addr(this->stack_);
this->uc_.uc_stack.ss_size = sg_makecontext_stack_size(smx_context_usable_stack_size);
- simgrid_makecontext(&this->uc_, smx_ctx_sysv_wrapper, this);
+#if PTH_STACKGROWTH == -1
+ ASAN_ONLY(this->asan_stack_ = static_cast<char*>(this->stack_) + smx_context_usable_stack_size);
+#else
+ ASAN_ONLY(this->asan_stack_ = this->stack_);
+#endif
+ UContext::make_ctx(&this->uc_, UContext::smx_ctx_sysv_wrapper, this);
} else {
- if (process != nullptr && sysv_maestro_context == nullptr)
- sysv_maestro_context = this;
+ if (process != nullptr && get_maestro() == nullptr)
+ set_maestro(this);
}
#if SIMGRID_HAVE_MC
if (MC_is_active() && has_code()) {
- MC_register_stack_area(this->stack_, process,
- &(this->uc_), smx_context_usable_stack_size);
+ MC_register_stack_area(this->stack_, process, &(this->uc_), smx_context_usable_stack_size);
}
#endif
}
-UContext::~UContext()
-{
- SIMIX_context_stack_delete(this->stack_);
-}
-
-}}} // namespace simgrid::kernel::context
+UContext::~UContext() = default;
-static void smx_ctx_sysv_wrapper(int first, ...)
+// The name of this function is currently hardcoded in the code (as string).
+// Do not change it without fixing those references as well.
+void UContext::smx_ctx_sysv_wrapper(int i1, int i2)
{
// Rebuild the Context* pointer from the integers:
- int ctx_addr[CTX_ADDR_LEN];
+ int ctx_addr[CTX_ADDR_LEN] = {i1, i2};
simgrid::kernel::context::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 context);
+
+ ASAN_FINISH_SWITCH(nullptr, &context->asan_ctx_->asan_stack_, &context->asan_ctx_->asan_stack_size_);
+ try {
+ (*context)();
+ } catch (simgrid::kernel::context::Context::StopRequest const&) {
+ XBT_DEBUG("Caught a StopRequest");
+ } catch (simgrid::Exception const& e) {
+ XBT_INFO("Actor killed by an uncatched exception %s", simgrid::xbt::demangle(typeid(e).name()).get());
+ throw;
}
- memcpy(&context, ctx_addr, sizeof(simgrid::kernel::context::UContext*));
-
- (*context)();
- context->stop();
+ context->Context::stop();
+ ASAN_ONLY(context->asan_stop_ = true);
+ context->suspend();
}
-namespace simgrid {
-namespace kernel {
-namespace context {
-
-void SerialUContext::stop()
-{
- Context::stop();
- this->suspend();
-}
-
-void SerialUContext::suspend()
+/** 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.
+ */
+void UContext::make_ctx(ucontext_t* ucp, void (*func)(int, int), UContext* arg)
{
- /* determine the next context */
- SerialUContext* next_context = nullptr;
- unsigned long int i = sysv_process_index++;
-
- if (i < simix_global->process_to_run.size()) {
- /* execute the next process */
- XBT_DEBUG("Run next process");
- next_context = static_cast<SerialUContext*>(simix_global->process_to_run[i]->context);
- } else {
- /* all processes were run, return to maestro */
- XBT_DEBUG("No more process to run");
- next_context = static_cast<SerialUContext*>(sysv_maestro_context);
- }
- SIMIX_context_set_current(next_context);
- swapcontext(&this->uc_, &next_context->uc_);
+ int ctx_addr[CTX_ADDR_LEN]{};
+ memcpy(ctx_addr, &arg, sizeof arg);
+ makecontext(ucp, (void (*)())func, 2, ctx_addr[0], ctx_addr[1]);
}
-// UContextSerial
-
-void SerialUContext::resume()
+void UContext::swap_into(SwappedContext* to_)
{
- SIMIX_context_set_current(this);
- swapcontext(&static_cast<SerialUContext*>(sysv_maestro_context)->uc_, &this->uc_);
+ UContext* to = static_cast<UContext*>(to_);
+ ASAN_ONLY(void* fake_stack = nullptr);
+ ASAN_ONLY(to->asan_ctx_ = from);
+ ASAN_START_SWITCH(from->asan_stop_ ? nullptr : &fake_stack, to->asan_stack_, to->asan_stack_size_);
+ swapcontext(&this->uc_, &to->uc_);
+ ASAN_FINISH_SWITCH(fake_stack, &from->asan_ctx_->asan_stack_, &from->asan_ctx_->asan_stack_size_);
}
-void ParallelUContext::stop()
-{
- UContext::stop();
- this->suspend();
-}
+// ParallelUContext
-/** Run one particular simulated process on the current thread. */
+/** Run one particular simulated process on the current thread.
+ *
+ * Only applied to the N first elements of the parmap array, where N is the amount of worker threads in the parmap.
+ * See ParallelUContext::run_all for details.
+ */
void ParallelUContext::resume()
{
-#if HAVE_THREAD_CONTEXTS
- // What is my containing body?
- uintptr_t 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 = static_cast<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 = &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
+ // Save the thread number (my body) in an os-thread-specific area
+ worker_id_ = threads_working_.fetch_add(1, std::memory_order_relaxed);
+ // Save my current soul (either maestro, or one of the minions) in a permanent area
+ SwappedContext* worker_context = static_cast<SwappedContext*>(self());
+ workers_context_[worker_id_] = worker_context;
+ // Switch my soul and the actor's one
+ Context::set_current(this);
+ worker_context->swap_into(this);
+ // No body runs that soul anymore at this point, but it is stored in a safe place.
+ // When the executed actor will do a blocking action, SIMIX_process_yield() will call suspend(), below.
}
/** 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).
+ * This function is called when a simulated process wants to yield back to the maestro in a blocking simcall,
+ * ie in SIMIX_process_yield().
+ *
+ * Actually, it does not really yield back to maestro, but directly into the next executable actor.
+ *
+ * This makes the parmap::apply awkward (see ParallelUContext::run_all()) because it only apply regularly
+ * on the few first elements of the array, but it saves a lot of context switches back to maestro,
+ * and directly forth to the next executable actor.
*/
void ParallelUContext::suspend()
{
-#if HAVE_THREAD_CONTEXTS
- /* determine the next context */
- // Get the next soul to embody now:
- boost::optional<smx_actor_t> next_work = sysv_parmap->next();
- ParallelUContext* next_context;
+ // Get some more work to directly swap into the next executable actor instead of yielding back to the parmap
+ boost::optional<smx_actor_t> next_work = parmap_->next();
+ SwappedContext* next_context;
if (next_work) {
- // There is a next soul to embody (ie, a next process to resume)
+ // There is a next soul to embody (ie, another executable actor)
XBT_DEBUG("Run next process");
- next_context = static_cast<ParallelUContext*>(next_work.get()->context);
+ next_context = static_cast<ParallelUContext*>(next_work.get()->context_);
} else {
- // All processes were run, go to the barrier
+ // All actors were run, go back to the parmap context
XBT_DEBUG("No more processes to run");
- // Get back the identity of my body that was stored when starting
- // the scheduling round
- uintptr_t worker_id =
- (uintptr_t) xbt_os_thread_get_specific(sysv_worker_id_key);
- // Deduce the initial soul of that body
- next_context = sysv_workers_context[worker_id];
+ // worker_id_ is the identity of my body, stored in thread_local when starting the scheduling round
+ next_context = workers_context_[worker_id_];
// When given that soul, the body will wait for the next scheduling round
}
- // Will contain the next soul to run, either simulated or initial minion's one
- ucontext_t* next_stack = &next_context->uc_;
-
- SIMIX_context_set_current(next_context);
- // Get that next soul:
- swapcontext(&this->uc_, next_stack);
-#endif
+ // Get the next soul to run, either from another actor or the initial minion's one
+ Context::set_current(next_context);
+ this->swap_into(next_context);
}
+XBT_PRIVATE ContextFactory* sysv_factory()
+{
+ XBT_VERB("Activating SYSV context factory");
+ return new UContextFactory();
+}
}}} // namespace simgrid::kernel::context
-
