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50daad3ff7bcaa7588c29fc746f04f111af6aa38
mercury/runtime/mercury_context.c
Paul Bone 50daad3ff7 Document a bug without fixing it. 
I've found the cause of a long standing race condition in the parallel
runtime system.  The fix is to properly design the engine state and
notification system in the parallel runtime system.  I've worked on a design
and committed a description.  I've started implementing the changes but found
a new different race condition.  I don't currently have the time to complete
this change, therefore I will commit the documentation of the current
problem and proposed solution.

runtime/mercury_context.c:
    As above, document the current race.

    Also comment on a bug where an idle engine could be notified of a
    context to execute.  This notification could be dropped in some
    situations causing the context to be lost.

runtime/notes/par_engine_state.txt:
runtime/notes/par_engine_state.dot:
    As above, document the proposed new engine state and notification
    design.
2012-09-04 11:08:38 +00:00

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/*
** vim: ts=4 sw=4 expandtab
*/
/*
INIT mercury_sys_init_scheduler_wrapper
ENDINIT
*/
/*
** Copyright (C) 1995-2007, 2009-2011 The University of Melbourne.
** This file may only be copied under the terms of the GNU Library General
** Public License - see the file COPYING.LIB in the Mercury distribution.
*/
/* mercury_context.c - handles multithreading stuff. */
#include "mercury_imp.h"
#include <stdio.h>
#ifdef MR_THREAD_SAFE
#include "mercury_thread.h"
#include "mercury_stm.h"
#ifndef MR_HIGHLEVEL_CODE
#include <semaphore.h>
#endif
#endif
#ifdef MR_CAN_DO_PENDING_IO
#include <sys/types.h> /* for fd_set */
#include <sys/time.h> /* for struct timeval */
#ifdef MR_HAVE_UNISTD_H
#include <unistd.h> /* for select() on OS X */
#endif
#endif
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
#include <math.h> /* for sqrt and pow */
#endif
#ifdef MR_HAVE_SCHED_H
#include <sched.h>
#endif
#ifdef MR_MINGW
#include <sys/time.h> /* for gettimeofday() */
#endif
#ifdef MR_WIN32
#include <sys/timeb.h> /* for _ftime() */
#endif
#if defined(MR_LL_PARALLEL_CONJ) && defined(MR_HAVE_HWLOC)
#include <hwloc.h>
#endif
#include "mercury_memory_handlers.h"
#include "mercury_context.h"
#include "mercury_engine.h" /* for `MR_memdebug' */
#include "mercury_threadscope.h" /* for data types and posting events */
#include "mercury_reg_workarounds.h" /* for `MR_fd*' stuff */
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
#define MR_PROFILE_PARALLEL_EXECUTION_FILENAME "parallel_execution_profile.txt"
#endif
/*---------------------------------------------------------------------------*/
static void
MR_init_context_maybe_generator(MR_Context *c, const char *id,
MR_GeneratorPtr gen);
/*---------------------------------------------------------------------------*/
#if defined(MR_LL_PARALLEL_CONJ)
static void
MR_milliseconds_from_now(struct timespec *timeout, unsigned int msecs);
/*
** These states are bitfields so they can be combined when passed to
** try_wake_engine. The definitions of the starts are:
**
** working the engine has work to do and is working on it.
**
** sleeping The engine has no work to do and is sleeping on it's sleep
** semaphore.
**
** idle The engine has recently finished it's work and is looking for
** more work before it goes to sleep. This state is useful when
** there are no sleeping engines but there are idle engines,
** signalling an idle engine will prevent it from sleeping and
** allow it to re-check the work queues.
**
** woken The engine was either sleeping or idle and has been signaled
** and possibly been given work to do. DO NOT signal these
** engines again doing so may leak work.
*/
#define ENGINE_STATE_WORKING 0x0001
#define ENGINE_STATE_SLEEPING 0x0002
#define ENGINE_STATE_IDLE 0x0004
#define ENGINE_STATE_WOKEN 0x0008
#define ENGINE_STATE_ALL 0xFFFF
struct engine_sleep_sync_i {
sem_t es_sleep_semaphore;
MercuryLock es_wake_lock;
volatile unsigned es_state;
volatile unsigned es_action;
union MR_engine_wake_action_data es_action_data;
};
#define CACHE_LINE_SIZE 64
#define PAD_CACHE_LINE(s) \
((CACHE_LINE_SIZE) > (s) ? (CACHE_LINE_SIZE) - (s) : 0)
typedef struct {
struct engine_sleep_sync_i d;
/*
** Padding ensures that engine sleep synchronisation data for different
** engines doesn't share cache lines.
*/
char padding[PAD_CACHE_LINE(sizeof(struct engine_sleep_sync_i))];
} engine_sleep_sync;
static
engine_sleep_sync *engine_sleep_sync_data;
#endif /* MR_LL_PARALLEL_CONJ */
/*
** The run queue is protected with MR_runqueue_lock and signalled with
** MR_runqueue_cond.
*/
MR_Context *MR_runqueue_head;
MR_Context *MR_runqueue_tail;
#ifdef MR_THREAD_SAFE
MercuryLock MR_runqueue_lock;
#endif
MR_PendingContext *MR_pending_contexts;
#ifdef MR_THREAD_SAFE
MercuryLock MR_pending_contexts_lock;
#endif
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
MR_bool MR_profile_parallel_execution = MR_FALSE;
#ifndef MR_HIGHLEVEL_CODE
static MR_Stats MR_profile_parallel_executed_global_sparks =
{ 0, 0, 0, 0 };
static MR_Stats MR_profile_parallel_executed_contexts = { 0, 0, 0, 0 };
static MR_Stats MR_profile_parallel_executed_nothing = { 0, 0, 0, 0 };
/* This cannot be static as it is used in macros by other modules. */
MR_Stats MR_profile_parallel_executed_local_sparks =
{ 0, 0, 0, 0 };
static MR_Integer MR_profile_parallel_contexts_created_for_sparks = 0;
/*
** We don't access these atomically. They are protected by the free context
** list lock.
*/
static MR_Integer MR_profile_parallel_small_context_reused = 0;
static MR_Integer MR_profile_parallel_regular_context_reused = 0;
static MR_Integer MR_profile_parallel_small_context_kept = 0;
static MR_Integer MR_profile_parallel_regular_context_kept = 0;
#endif /* ! MR_HIGHLEVEL_CODE */
#endif /* MR_PROFILE_PARALLEL_EXECUTION_SUPPORT */
/*
** Local variables for thread pinning.
*/
#if defined(MR_LL_PARALLEL_CONJ) && defined(MR_HAVE_THREAD_PINNING)
MR_bool MR_thread_pinning = MR_FALSE;
static MercuryLock MR_thread_pinning_lock;
static unsigned MR_num_threads_left_to_pin;
static unsigned MR_num_processors;
MR_Unsigned MR_primordial_thread_cpu;
#ifdef MR_HAVE_HWLOC
static hwloc_topology_t MR_hw_topology;
static hwloc_cpuset_t MR_hw_available_pus = NULL;
#else /* MR_HAVE_SCHED_SETAFFINITY */
static cpu_set_t *MR_available_cpus;
/* The number of CPUs that MR_available_cpus can refer to */
static unsigned MR_cpuset_size = 0;
#endif
#endif
#if defined(MR_LL_PARALLEL_CONJ) && \
defined(MR_PROFILE_PARALLEL_EXECUTION_SUPPORT)
/*
** This is used to give each context its own unique ID. It is accessed with
** atomic operations.
*/
static MR_ContextId MR_next_context_id = 0;
/*
** Allocate a context ID.
*/
static MR_ContextId
allocate_context_id(void);
#endif
/*
** free_context_list and free_small_context_list are a global linked lists
** of unused context structures, with regular and small stacks respectively.
** If the MR_MemoryZone pointers are not NULL, then they point to allocated
** MR_MemoryZones.
*/
static MR_Context *free_context_list = NULL;
#ifndef MR_STACK_SEGMENTS
static MR_Context *free_small_context_list = NULL;
#endif
#ifdef MR_THREAD_SAFE
static MercuryLock free_context_list_lock;
#endif
#ifdef MR_LL_PARALLEL_CONJ
MR_Integer volatile MR_num_idle_engines = 0;
MR_Unsigned volatile MR_num_exited_engines = 0;
static MR_Integer volatile MR_num_outstanding_contexts = 0;
static sem_t shutdown_semaphore;
static MercuryLock MR_par_cond_stats_lock;
/*
** The spark deques are kept in engine id order.
**
** This array will contain MR_num_threads pointers to deques.
*/
MR_SparkDeque **MR_spark_deques = NULL;
#endif
/*---------------------------------------------------------------------------*/
#ifdef MR_LL_PARALLEL_CONJ
/*
** Try to wake up a sleeping engine and tell it to do action. The engine
** is only woken if the engine is in one of the states in the bitfield states.
** If the engine is woken, this function returns MR_TRUE, otherwise it
** returns MR_FALSE.
*/
static MR_bool
try_wake_engine(MR_EngineId engine_id, int action,
union MR_engine_wake_action_data *action_data, unsigned states);
#endif
/*
** Write out the profiling data that we collect during execution.
*/
static void
MR_write_out_profiling_parallel_execution(void);
#if defined(MR_LL_PARALLEL_CONJ)
static void
MR_setup_thread_pinning(void);
static MR_bool
MR_do_pin_thread(int cpu);
/*
** Determine which CPU this thread is currently running on.
*/
static int
MR_current_cpu(void);
/*
** Reset or initialize the cpuset that tracks which CPUs are available for
** binding.
*/
static void
MR_reset_available_cpus(void);
/*
** Mark the given CPU as unavailable for thread pinning. This may mark other
** CPUs as unavailable, if, for instance they share resources with this
** processor and we can place other tasks elsewhere to avoid this sharing.
** These resources are usually only considered for hardware threads that share
** cores.
*/
static void
MR_make_cpu_unavailable(int cpu);
#endif
/*---------------------------------------------------------------------------*/
void
MR_init_context_stuff(void)
{
#ifdef MR_LL_PARALLEL_CONJ
unsigned i;
#endif
#ifdef MR_THREAD_SAFE
pthread_mutex_init(&MR_runqueue_lock, MR_MUTEX_ATTR);
pthread_mutex_init(&free_context_list_lock, MR_MUTEX_ATTR);
pthread_mutex_init(&MR_pending_contexts_lock, MR_MUTEX_ATTR);
#ifdef MR_LL_PARALLEL_CONJ
#ifdef MR_DEBUG_RUNTIME_GRANULARITY_CONTROL
pthread_mutex_init(&MR_par_cond_stats_lock, MR_MUTEX_ATTR);
#endif
sem_init(&shutdown_semaphore, 0, 0);
#endif
pthread_mutex_init(&MR_STM_lock, MR_MUTEX_ATTR);
#ifdef MR_HIGHLEVEL_CODE
MR_KEY_CREATE(&MR_backjump_handler_key, NULL);
MR_KEY_CREATE(&MR_backjump_next_choice_id_key, (void *)0);
#endif
#ifdef MR_LL_PARALLEL_CONJ
#if defined(MR_HAVE_THREAD_PINNING)
MR_setup_thread_pinning();
#endif
MR_granularity_wsdeque_length =
MR_granularity_wsdeque_length_factor * MR_num_threads;
MR_spark_deques = MR_GC_NEW_ARRAY_ATTRIB(MR_SparkDeque*,
MR_num_threads, MR_ALLOC_SITE_RUNTIME);
engine_sleep_sync_data = MR_GC_NEW_ARRAY_ATTRIB(engine_sleep_sync,
MR_num_threads, MR_ALLOC_SITE_RUNTIME);
for (i = 0; i < MR_num_threads; i++) {
MR_spark_deques[i] = NULL;
sem_init(&(engine_sleep_sync_data[i].d.es_sleep_semaphore), 0, 0);
pthread_mutex_init(&(engine_sleep_sync_data[i].d.es_wake_lock),
MR_MUTEX_ATTR);
/*
** All engines are initially working (because telling them to wake up
** before they are started would be useless).
*/
engine_sleep_sync_data[i].d.es_state = ENGINE_STATE_WORKING;
engine_sleep_sync_data[i].d.es_action = MR_ENGINE_ACTION_NONE;
}
#endif
#endif /* MR_THREAD_SAFE */
}
/*
** Pin the primordial thread first to the CPU it is currently using
** (if support is available for thread pinning).
*/
#if defined(MR_HAVE_THREAD_PINNING) && defined(MR_LL_PARALLEL_CONJ)
static unsigned
MR_pin_thread_no_locking(void)
{
unsigned cpu;
unsigned i = 0;
cpu = MR_current_cpu();
#ifdef MR_DEBUG_THREAD_PINNING
fprintf(stderr, "Currently running on cpu %d\n", cpu);
#endif
for (i = 0; (i < MR_num_processors) && MR_thread_pinning; i++) {
if (MR_do_pin_thread((cpu + i) % MR_num_processors)) {
#ifdef MR_DEBUG_THREAD_PINNING
fprintf(stderr, "Pinned to cpu %d\n", (cpu + i) % MR_num_processors);
fprintf(stderr, "Now running on cpu %d\n", MR_current_cpu());
#endif
MR_num_threads_left_to_pin--;
MR_make_cpu_unavailable((cpu + i) % MR_num_processors);
return (cpu + i) % MR_num_processors;
}
if (!MR_thread_pinning) {
/*
** If MR_thread_pinning becomes false then an error prevented us
** from pinning the thread.
** When we fail to pin a thread but MR_thread_pinning remains true
** it means that that CPU has already had a thread pinned to it.
*/
fprintf(stderr, "Couldn't pin Mercury engine to processor");
break;
}
}
return cpu;
}
unsigned
MR_pin_thread(void)
{
unsigned cpu;
MR_LOCK(&MR_thread_pinning_lock, "MR_pin_thread");
cpu = MR_pin_thread_no_locking();
MR_UNLOCK(&MR_thread_pinning_lock, "MR_pin_thread");
return cpu;
}
void
MR_pin_primordial_thread(void)
{
/*
** We don't need locking to pin the primordial thread as it is called
** before any other threads exist.
*/
MR_primordial_thread_cpu = MR_pin_thread_no_locking();
}
static void MR_setup_thread_pinning(void)
{
unsigned num_processors;
#ifdef MR_HAVE_HWLOC
if (-1 == hwloc_topology_init(&MR_hw_topology)) {
MR_fatal_error("Error allocating libhwloc topology object");
}
if (-1 == hwloc_topology_load(MR_hw_topology)) {
MR_fatal_error("Error detecting hardware topology (hwloc)");
}
#endif
/*
** Setup num processors
*/
MR_reset_available_cpus();
#ifdef MR_HAVE_HWLOC
num_processors = hwloc_cpuset_weight(MR_hw_available_pus);
#elif defined(MR_HAVE_SCHED_GETAFFINITY)
/*
** This looks redundant but its not. MR_num_processors is a guess that was
** gathered by using sysconf. But the number of CPUs in the CPU_SET is the
** actual number of CPUs that this process is restricted to.
*/
num_processors = CPU_COUNT_S(MR_cpuset_size, MR_available_cpus);
#endif
MR_num_processors = num_processors;
/*
** If MR_num_threads is unset, configure it to match number of processors
** on the system. If we do this, then we prepare to set processor
** affinities later on.
*/
if (MR_num_threads == 0) {
MR_num_threads = num_processors;
}
MR_num_threads_left_to_pin = MR_num_threads;
#ifdef MR_DEBUG_THREAD_PINNING
fprintf(stderr, "Detected %d available processors, will use %d threads\n",
MR_num_processors, MR_num_threads);
#endif
pthread_mutex_init(&MR_thread_pinning_lock, MR_MUTEX_ATTR);
/*
** Comment this back in to enable thread pinning by default
** if we autodetected the number of CPUs without error.
*/
#if 0
if (MR_num_processors > 1) {
MR_thread_pinning = MR_TRUE;
}
#endif
}
/*
** Determine which CPU this thread is currently running on.
*/
static int MR_current_cpu(void)
{
#if defined(MR_HAVE_SCHED_GETCPU)
int os_cpu;
#if defined(MR_HAVE_HWLOC)
hwloc_obj_t pu;
#endif
os_cpu = sched_getcpu();
if (-1 == os_cpu) {
os_cpu = 0;
if (MR_thread_pinning) {
perror("Warning: unable to determine the current CPU for "
"this thread: ");
}
}
#if defined(MR_HAVE_HWLOC)
pu = hwloc_get_pu_obj_by_os_index(MR_hw_topology, os_cpu);
return pu->logical_index;
#else
return os_cpu;
#endif
#else /* ! MR_HAVE_SCHED_GETCPU */
/* We have no idea! */
return 0;
#endif
}
static MR_bool
MR_do_pin_thread(int cpu)
{
/*
** Make sure that we're allowed to bind to this CPU.
*/
#if defined(MR_HAVE_HWLOC)
hwloc_obj_t pu;
if (hwloc_cpuset_iszero(MR_hw_available_pus)) {
/*
** Each available CPU already has a thread pinned to it. Reset the
** available_pus set so that we can oversubscribe CPUs but still
** attempt to balance load.
*/
MR_reset_available_cpus();
}
pu = hwloc_get_obj_by_type(MR_hw_topology, HWLOC_OBJ_PU, cpu);
if (!hwloc_cpuset_intersects(MR_hw_available_pus, pu->cpuset)) {
return MR_FALSE;
}
#elif defined(MR_HAVE_SCHED_SETAFFINITY)
if (CPU_COUNT_S(MR_cpuset_size, MR_available_cpus) == 0) {
/*
** As above, reset the available cpus.
*/
MR_reset_available_cpus();
}
if (!CPU_ISSET_S(cpu, MR_cpuset_size, MR_available_cpus)) {
return MR_FALSE;
}
#endif
#if defined(MR_HAVE_HWLOC)
errno = hwloc_set_cpubind(MR_hw_topology, pu->cpuset,
HWLOC_CPUBIND_THREAD);
if (errno != 0) {
perror("Warning: Couldn't set CPU affinity: ");
MR_thread_pinning = MR_FALSE;
return MR_FALSE;
}
#elif defined(MR_HAVE_SCHED_SETAFFINITY)
cpu_set_t *cpus;
cpus = CPU_ALLOC(MR_num_processors);
CPU_ZERO_S(MR_cpuset_size, cpus);
CPU_SET_S(cpu, MR_cpuset_size, cpus);
if (sched_setaffinity(0, MR_cpuset_size, cpus) == -1) {
perror("Warning: Couldn't set CPU affinity: ");
/*
** If this failed once, it will probably fail again,
** so we disable it.
*/
MR_thread_pinning = MR_FALSE;
return MR_FALSE;
}
#endif
return MR_TRUE;
}
static void MR_reset_available_cpus(void)
{
#if defined(MR_HAVE_HWLOC)
hwloc_cpuset_t inherited_binding;
/*
** Gather the cpuset that our parent process bound this process to.
**
** (For information about how to deliberately restrict a process and it's
** sub-processors to a set of CPUs on Linux see cpuset(7).
*/
inherited_binding = hwloc_cpuset_alloc();
hwloc_get_cpubind(MR_hw_topology, inherited_binding, HWLOC_CPUBIND_PROCESS);
/*
** Set the available processors to the union of inherited_binding and the
** cpuset we're allowed to use as reported by libhwloc. In my tests with
** libhwloc_1.0-1 (Debian) hwloc reported that all cpus on the system are
** avaliable, it didn't exclude cpus not in the processor's cpuset(7).
*/
if (MR_hw_available_pus == NULL) {
MR_hw_available_pus = hwloc_cpuset_alloc();
}
hwloc_cpuset_and(MR_hw_available_pus, inherited_binding,
hwloc_topology_get_allowed_cpuset(MR_hw_topology));
hwloc_cpuset_free(inherited_binding);
#elif defined(MR_HAVE_SCHED_GETAFFINITY)
unsigned cpuset_size;
unsigned num_processors;
if (MR_cpuset_size) {
cpuset_size = MR_cpuset_size;
num_processors = MR_num_processors;
} else {
#if defined(MR_HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
num_processors = sysconf(_SC_NPROCESSORS_ONLN);
#else
/*
** Make the CPU set at least 32 processors wide.
*/
num_processors = 32;
#endif
cpuset_size = CPU_ALLOC_SIZE(num_processors);
MR_cpuset_size = cpuset_size;
}
if (MR_available_cpus == NULL) {
MR_available_cpus = CPU_ALLOC(num_processors);
}
if (-1 == sched_getaffinity(0, cpuset_size, MR_available_cpus))
{
perror("Couldn't get CPU affinity");
MR_thread_pinning = MR_FALSE;
CPU_FREE(MR_available_cpus);
MR_available_cpus = NULL;
}
#endif
}
#if defined(MR_HAVE_HWLOC)
static MR_bool MR_make_pu_unavailable(const struct hwloc_obj *pu);
#endif
static void MR_make_cpu_unavailable(int cpu)
{
#if defined(MR_HAVE_HWLOC)
hwloc_obj_t pu;
pu = hwloc_get_obj_by_type(MR_hw_topology, HWLOC_OBJ_PU, cpu);
MR_make_pu_unavailable(pu);
#elif defined(MR_HAVE_SCHED_SETAFFINITY)
CPU_CLR_S(cpu, MR_cpuset_size, MR_available_cpus);
#endif
}
#if defined(MR_HAVE_HWLOC)
static MR_bool MR_make_pu_unavailable(const struct hwloc_obj *pu) {
hwloc_obj_t core;
static int siblings_to_make_unavailable;
int i;
#ifdef MR_DEBUG_THREAD_PINNING
char * cpusetstr;
hwloc_cpuset_asprintf(&cpusetstr, MR_hw_available_pus);
fprintf(stderr, "Old available CPU set: %s\n", cpusetstr);
free(cpusetstr);
hwloc_cpuset_asprintf(&cpusetstr, pu->cpuset);
fprintf(stderr, "Making this CPU set unavailable: %s\n", cpusetstr);
free(cpusetstr);
#endif
hwloc_cpuset_andnot(MR_hw_available_pus, MR_hw_available_pus, pu->cpuset);
#ifdef MR_DEBUG_THREAD_PINNING
hwloc_cpuset_asprintf(&cpusetstr, MR_hw_available_pus);
fprintf(stderr, "New available CPU set: %s\n", cpusetstr);
free(cpusetstr);
#endif
siblings_to_make_unavailable = hwloc_cpuset_weight(MR_hw_available_pus) -
MR_num_threads_left_to_pin;
if (siblings_to_make_unavailable > 0) {
/*
** Remove sibling processing units that share a core with the one we've just removed.
*/
core = pu->parent;
if (core->type != HWLOC_OBJ_CORE) {
return MR_FALSE;
}
for (i = 0;
(i < core->arity && siblings_to_make_unavailable > 0);
i++) {
if (core->children[i] == pu) {
continue;
}
if (hwloc_cpuset_intersects(core->children[i]->cpuset,
MR_hw_available_pus)) {
if (!MR_make_pu_unavailable(core->children[i])) {
return MR_FALSE;
}
}
}
}
return MR_TRUE;
}
#endif
#endif /* MR_HAVE_THREAD_PINNING && MR_LL_PARALLEL_CONJ */
void
MR_finalize_context_stuff(void)
{
#ifdef MR_THREAD_SAFE
pthread_mutex_destroy(&MR_runqueue_lock);
pthread_mutex_destroy(&free_context_list_lock);
#ifdef MR_LL_PARALLEL_CONJ
sem_destroy(&shutdown_semaphore);
#endif
#endif
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
if (MR_profile_parallel_execution) {
MR_write_out_profiling_parallel_execution();
}
#endif
}
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
static int
fprint_stats(FILE *stream, const char *message, MR_Stats *stats);
/*
** Write out the profiling data for parallel execution.
**
** This writes out a flat text file which may be parsed by a machine or easily
** read by a human. There is no advantage in using a binary format since we
** do this once at the end of execution and it is a small amount of data.
** Therefore we use a text file, since it has the advantage of being human
** readable.
*/
static void
MR_write_out_profiling_parallel_execution(void)
{
FILE *file;
int result;
file = fopen(MR_PROFILE_PARALLEL_EXECUTION_FILENAME, "w");
if (NULL == file) goto Error;
result = fprintf(file, "Mercury parallel execution profiling data\n\n");
if (result < 0) goto Error;
if (MR_cpu_cycles_per_sec) {
result = fprintf(file, "CPU cycles per second: %ld\n",
MR_cpu_cycles_per_sec);
if (result < 0) goto Error;
}
result = fprint_stats(file, "MR_do_runnext(): global sparks executed",
&MR_profile_parallel_executed_global_sparks);
if (result < 0) goto Error;
result = fprint_stats(file, "MR_do_runnext(): global contexts resumed",
&MR_profile_parallel_executed_contexts);
if (result < 0) goto Error;
result = fprint_stats(file, "MR_do_runnext(): executed nothing",
&MR_profile_parallel_executed_nothing);
if (result < 0) goto Error;
result = fprint_stats(file, "Local sparks executed",
&MR_profile_parallel_executed_local_sparks);
if (result < 0) goto Error;
result = fprintf(file, "Contexts created for global spark execution: %d\n",
MR_profile_parallel_contexts_created_for_sparks);
if (result < 0) goto Error;
result = fprintf(file, "Number of times a small context was reused: %d\n",
MR_profile_parallel_small_context_reused);
if (result < 0) goto Error;
result = fprintf(file,
"Number of times a regular context was reused: %d\n",
MR_profile_parallel_regular_context_reused);
if (result < 0) goto Error;
result = fprintf(file,
"Number of times a small context was kept for later use: %d\n",
MR_profile_parallel_small_context_kept);
if (result < 0) goto Error;
result = fprintf(file,
"Number of times a regular context was kept for later use: %d\n",
MR_profile_parallel_regular_context_kept);
if (result < 0) goto Error;
if (fclose(file) != 0) goto Error;
return;
Error:
perror(MR_PROFILE_PARALLEL_EXECUTION_FILENAME);
abort();
}
#define MR_FPRINT_STATS_FORMAT_STRING_FULL \
("%s: count %" MR_INTEGER_LENGTH_MODIFIER "u (%" \
MR_INTEGER_LENGTH_MODIFIER "ur, %" MR_INTEGER_LENGTH_MODIFIER \
"unr), average %.0f, standard deviation %.0f\n")
#define MR_FPRINT_STATS_FORMAT_STRING_SINGLE \
("%s: count %" MR_INTEGER_LENGTH_MODIFIER "u (%" \
MR_INTEGER_LENGTH_MODIFIER "ur, %" MR_INTEGER_LENGTH_MODIFIER \
"unr), sample %ul\n")
#define MR_FPRINT_STATS_FORMAT_STRING_NONE \
("%s: count %" MR_INTEGER_LENGTH_MODIFIER "u (%" \
MR_INTEGER_LENGTH_MODIFIER "ur, %" MR_INTEGER_LENGTH_MODIFIER "unr)\n")
static int
fprint_stats(FILE *stream, const char *message, MR_Stats *stats)
{
MR_Unsigned count;
double average;
double sum_squared_over_n;
double standard_deviation;
count = (unsigned)(stats->MR_stat_count_recorded +
stats->MR_stat_count_not_recorded);
if (stats->MR_stat_count_recorded > 1) {
average = (double)stats->MR_stat_sum /
(double)stats->MR_stat_count_recorded;
sum_squared_over_n = pow((double)stats->MR_stat_sum,2.0)/
(double)stats->MR_stat_count_recorded;
standard_deviation =
sqrt(((double)stats->MR_stat_sum_squares - sum_squared_over_n) /
(double)(stats->MR_stat_count_recorded - 1));
return fprintf(stream, MR_FPRINT_STATS_FORMAT_STRING_FULL, message,
count, stats->MR_stat_count_recorded,
stats->MR_stat_count_not_recorded, average, standard_deviation);
} else if (stats->MR_stat_count_recorded == 1) {
return fprintf(stream, MR_FPRINT_STATS_FORMAT_STRING_SINGLE,
message, count, stats->MR_stat_count_recorded,
stats->MR_stat_count_not_recorded, stats->MR_stat_sum);
} else {
return fprintf(stream, MR_FPRINT_STATS_FORMAT_STRING_NONE,
message, count, stats->MR_stat_count_recorded,
stats->MR_stat_count_not_recorded);
}
};
#endif /* MR_PROFILE_PARALLEL_EXECUTION_SUPPORT */
static void
MR_init_context_maybe_generator(MR_Context *c, const char *id,
MR_GeneratorPtr gen)
{
const char *detstack_name;
const char *nondetstack_name;
size_t detstack_size;
size_t nondetstack_size;
c->MR_ctxt_id = id;
c->MR_ctxt_next = NULL;
c->MR_ctxt_resume = NULL;
#ifdef MR_THREAD_SAFE
c->MR_ctxt_resume_owner_engine = 0;
c->MR_ctxt_resume_engine_required = MR_FALSE;
c->MR_ctxt_resume_c_depth = 0;
c->MR_ctxt_saved_owners = NULL;
#endif
#ifndef MR_HIGHLEVEL_CODE
c->MR_ctxt_succip = MR_ENTRY(MR_do_not_reached);
switch (c->MR_ctxt_size) {
case MR_CONTEXT_SIZE_REGULAR:
detstack_name = "detstack";
nondetstack_name = "nondetstack";
detstack_size = MR_detstack_size;
nondetstack_size = MR_nondetstack_size;
break;
#ifndef MR_STACK_SEGMENTS
case MR_CONTEXT_SIZE_SMALL:
detstack_name = "small_detstack";
nondetstack_name = "small_nondetstack";
detstack_size = MR_small_detstack_size;
nondetstack_size = MR_small_nondetstack_size;
break;
#endif
}
#ifdef MR_DEBUG_CONTEXT_CREATION_SPEED
MR_debug_log_message("Allocating det stack");
#endif
if (c->MR_ctxt_detstack_zone == NULL) {
if (gen != NULL) {
c->MR_ctxt_detstack_zone = MR_create_or_reuse_zone("gen_detstack",
MR_gen_detstack_size, MR_next_offset(),
MR_gen_detstack_zone_size, MR_default_handler);
} else {
c->MR_ctxt_detstack_zone = MR_create_or_reuse_zone(detstack_name,
detstack_size, MR_next_offset(),
MR_detstack_zone_size, MR_default_handler);
}
if (c->MR_ctxt_prev_detstack_zones != NULL) {
/*
** We may be able to reuse a previously allocated stack, but
** a context should be reused only when its stacks are empty.
*/
MR_fatal_error("MR_init_context_maybe_generator: prev det stack");
}
}
#ifdef MR_DEBUG_CONTEXT_CREATION_SPEED
MR_debug_log_message("done");
#endif
c->MR_ctxt_prev_detstack_zones = NULL;
c->MR_ctxt_sp = c->MR_ctxt_detstack_zone->MR_zone_min;
#ifdef MR_DEBUG_CONTEXT_CREATION_SPEED
MR_debug_log_message("Allocating nondet stack");
#endif
if (c->MR_ctxt_nondetstack_zone == NULL) {
if (gen != NULL) {
c->MR_ctxt_nondetstack_zone =
MR_create_or_reuse_zone("gen_nondetstack",
MR_gen_nondetstack_size, MR_next_offset(),
MR_gen_nondetstack_zone_size, MR_default_handler);
} else {
c->MR_ctxt_nondetstack_zone =
MR_create_or_reuse_zone(nondetstack_name,
nondetstack_size, MR_next_offset(),
MR_nondetstack_zone_size, MR_default_handler);
}
if (c->MR_ctxt_prev_nondetstack_zones != NULL) {
/*
** We may be able to reuse a previously allocated stack, but
** a context should be reused only when its stacks are empty.
*/
MR_fatal_error(
"MR_init_context_maybe_generator: prev nondet stack");
}
}
#ifdef MR_DEBUG_CONTEXT_CREATION_SPEED
MR_debug_log_message("done");
#endif
c->MR_ctxt_prev_nondetstack_zones = NULL;
/*
** Note that maxfr and curfr point to the last word in the frame,
** not to the first word, so we need to add the size of the frame,
** minus one word, to the base address to get the maxfr/curfr pointer
** for the first frame on the nondet stack.
*/
c->MR_ctxt_maxfr = c->MR_ctxt_nondetstack_zone->MR_zone_min +
MR_NONDET_FIXED_SIZE - 1;
c->MR_ctxt_curfr = c->MR_ctxt_maxfr;
MR_redoip_slot_word(c->MR_ctxt_curfr) = (MR_Word)
MR_ENTRY(MR_do_not_reached);
MR_redofr_slot_word(c->MR_ctxt_curfr) = (MR_Word) NULL;
MR_prevfr_slot_word(c->MR_ctxt_curfr) = (MR_Word) NULL;
MR_succip_slot_word(c->MR_ctxt_curfr) = (MR_Word)
MR_ENTRY(MR_do_not_reached);
MR_succfr_slot_word(c->MR_ctxt_curfr) = (MR_Word) NULL;
#ifdef MR_USE_MINIMAL_MODEL_STACK_COPY
if (gen != NULL) {
MR_fatal_error("MR_init_context_maybe_generator: "
"generator and stack_copy");
}
if (c->MR_ctxt_genstack_zone == NULL) {
c->MR_ctxt_genstack_zone = MR_create_or_reuse_zone("genstack",
MR_genstack_size, MR_next_offset(),
MR_genstack_zone_size, MR_default_handler);
}
c->MR_ctxt_gen_next = 0;
if (c->MR_ctxt_cutstack_zone == NULL) {
c->MR_ctxt_cutstack_zone = MR_create_or_reuse_zone("cutstack",
MR_cutstack_size, MR_next_offset(),
MR_cutstack_zone_size, MR_default_handler);
}
c->MR_ctxt_cut_next = 0;
if (c->MR_ctxt_pnegstack_zone == NULL) {
c->MR_ctxt_pnegstack_zone = MR_create_or_reuse_zone("pnegstack",
MR_pnegstack_size, MR_next_offset(),
MR_pnegstack_zone_size, MR_default_handler);
}
c->MR_ctxt_pneg_next = 0;
#endif /* MR_USE_MINIMAL_MODEL_STACK_COPY */
#ifdef MR_USE_MINIMAL_MODEL_OWN_STACKS
c->MR_ctxt_owner_generator = gen;
#endif /* MR_USE_MINIMAL_MODEL_OWN_STACKS */
#ifdef MR_LL_PARALLEL_CONJ
c->MR_ctxt_parent_sp = NULL;
#endif /* MR_LL_PARALLEL_CONJ */
#endif /* !MR_HIGHLEVEL_CODE */
#ifdef MR_USE_TRAIL
if (gen != NULL) {
MR_fatal_error("MR_init_context_maybe_generator: generator and trail");
}
if (c->MR_ctxt_trail_zone == NULL) {
c->MR_ctxt_trail_zone = MR_create_or_reuse_zone("trail",
MR_trail_size, MR_next_offset(),
MR_trail_zone_size, MR_default_handler);
}
c->MR_ctxt_trail_ptr =
(MR_TrailEntry *) c->MR_ctxt_trail_zone->MR_zone_min;
c->MR_ctxt_ticket_counter = 1;
c->MR_ctxt_ticket_high_water = 1;
#endif
#ifndef MR_HIGHLEVEL_CODE
c->MR_ctxt_backjump_handler = NULL;
c->MR_ctxt_backjump_next_choice_id = 0;
#endif
#ifndef MR_CONSERVATIVE_GC
if (gen != NULL) {
MR_fatal_error("MR_init_context: generator and no conservative gc");
}
c->MR_ctxt_hp = NULL;
c->MR_ctxt_min_hp_rec = NULL;
#endif
#ifdef MR_EXEC_TRACE_INFO_IN_CONTEXT
c->MR_ctxt_call_seqno = 0;
c->MR_ctxt_call_depth = 0;
c->MR_ctxt_event_number = 0;
#endif
/* The caller is responsible for initialising this field. */
c->MR_ctxt_thread_local_mutables = NULL;
}
MR_Context *
MR_create_context(const char *id, MR_ContextSize ctxt_size, MR_Generator *gen)
{
MR_Context *c = NULL;
#ifdef MR_LL_PARALLEL_CONJ
MR_atomic_inc_int(&MR_num_outstanding_contexts);
#endif
MR_LOCK(&free_context_list_lock, "create_context");
/*
** Regular contexts have stacks at least as big as small contexts,
** so we can return a regular context in place of a small context
** if one is already available.
*/
#ifndef MR_STACK_SEGMENTS
if (ctxt_size == MR_CONTEXT_SIZE_SMALL && free_small_context_list) {
c = free_small_context_list;
free_small_context_list = c->MR_ctxt_next;
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
if (MR_profile_parallel_execution) {
MR_profile_parallel_small_context_reused++;
}
#endif
}
#endif
if (c == NULL && free_context_list != NULL) {
c = free_context_list;
free_context_list = c->MR_ctxt_next;
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
if (MR_profile_parallel_execution) {
MR_profile_parallel_regular_context_reused++;
}
#endif
}
MR_UNLOCK(&free_context_list_lock, "create_context i");
if (c != NULL) {
#ifdef MR_THREADSCOPE
MR_Unsigned old_id = c->MR_ctxt_num_id;
c->MR_ctxt_num_id = allocate_context_id();
MR_threadscope_post_reuse_context(c, old_id);
#endif
#ifdef MR_DEBUG_STACK_SEGMENTS
MR_debug_log_message("Re-used an old context: %p", c);
#endif
}
else {
c = MR_GC_NEW_ATTRIB(MR_Context, MR_ALLOC_SITE_RUNTIME);
#ifdef MR_DEBUG_STACK_SEGMENTS
if (c) {
MR_debug_log_message("Creating new context: %p", c);
}
#endif
c->MR_ctxt_size = ctxt_size;
#ifndef MR_HIGHLEVEL_CODE
c->MR_ctxt_detstack_zone = NULL;
c->MR_ctxt_nondetstack_zone = NULL;
#endif
#ifdef MR_USE_TRAIL
c->MR_ctxt_trail_zone = NULL;
#endif
#ifdef MR_THREADSCOPE
c->MR_ctxt_num_id = allocate_context_id();
MR_threadscope_post_create_context(c);
#endif
}
#ifdef MR_DEBUG_CONTEXT_CREATION_SPEED
MR_debug_log_message("Calling MR_init_context_maybe_generator");
#endif
MR_init_context_maybe_generator(c, id, gen);
return c;
}
/*
** TODO: We should gc the cached contexts, or otherwise not cache too many.
*/
void
MR_release_context(MR_Context *c)
{
MR_assert(c);
#ifdef MR_THREADSCOPE
MR_threadscope_post_release_context(c);
#endif
#ifdef MR_THREAD_SAFE
MR_assert(c->MR_ctxt_saved_owners == NULL);
#endif
/*
** TODO: When retrieving a context from the cached contexts, try to
** retrieve one with a matching engine ID, or give each engine a local
** cache of spare contexts.
#ifdef MR_LL_PARALLEL_CONJ
c->MR_ctxt_resume_owner_engine = MR_ENGINE(MR_eng_id);
#endif
*/
/* XXX not sure if this is an overall win yet */
#if 0 && defined(MR_CONSERVATIVE_GC) && !defined(MR_HIGHLEVEL_CODE)
/* Clear stacks to prevent retention of data. */
MR_clear_zone_for_GC(c->MR_ctxt_detstack_zone,
c->MR_ctxt_detstack_zone->MR_zone_min);
MR_clear_zone_for_GC(c->MR_ctxt_nondetstack_zone,
c->MR_ctxt_nondetstack_zone->MR_zone_min);
#endif /* defined(MR_CONSERVATIVE_GC) && !defined(MR_HIGHLEVEL_CODE) */
#ifdef MR_LL_PARALLEL_CONJ
MR_atomic_dec_int(&MR_num_outstanding_contexts);
#endif
MR_LOCK(&free_context_list_lock, "destroy_context");
switch (c->MR_ctxt_size) {
case MR_CONTEXT_SIZE_REGULAR:
c->MR_ctxt_next = free_context_list;
free_context_list = c;
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
if (MR_profile_parallel_execution) {
MR_profile_parallel_regular_context_kept++;
}
#endif
break;
#ifndef MR_STACK_SEGMENTS
case MR_CONTEXT_SIZE_SMALL:
c->MR_ctxt_next = free_small_context_list;
free_small_context_list = c;
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
if (MR_profile_parallel_execution) {
MR_profile_parallel_small_context_kept++;
}
#endif
break;
#endif
}
MR_UNLOCK(&free_context_list_lock, "destroy_context");
}
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
static MR_ContextId
allocate_context_id(void) {
return MR_atomic_add_and_fetch_int(&MR_next_context_id, 1);
}
#endif
#ifdef MR_LL_PARALLEL_CONJ
/* Search for a ready context which we can handle. */
static MR_Context *
MR_find_ready_context(void)
{
MR_Context *cur;
MR_Context *prev;
MR_Context *preferred_context;
MR_Context *preferred_context_prev;
MR_EngineId engine_id = MR_ENGINE(MR_eng_id);
MR_Unsigned depth = MR_ENGINE(MR_eng_c_depth);
/* XXX check pending io */
/*
** Give preference to contexts as follows:
**
** A context that must be run on this engine.
** A context that prefers to be run on this engine.
** Any runnable context that may be ran on this engine.
**
** TODO: There are other scheduling decisions we should test, such as
** running older versus younger contexts, or more recently stopped/runnable
** contexts.
*/
cur = MR_runqueue_head;
prev = NULL;
preferred_context = NULL;
preferred_context_prev = NULL;
while (cur != NULL) {
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Eng: %d, c_depth: %d, Considering context %p\n",
MR_SELF_THREAD_ID, engine_id, depth, cur);
}
#endif
if (cur->MR_ctxt_resume_engine_required == MR_TRUE) {
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Context requires engine %d and c_depth %d\n",
MR_SELF_THREAD_ID, cur->MR_ctxt_resume_owner_engine,
cur->MR_ctxt_resume_c_depth);
}
#endif
if ((cur->MR_ctxt_resume_owner_engine == engine_id) &&
(cur->MR_ctxt_resume_c_depth == depth))
{
preferred_context = cur;
preferred_context_prev = prev;
cur->MR_ctxt_resume_engine_required = MR_FALSE;
/*
** This is the best thread to resume.
*/
break;
}
} else {
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Context prefers engine %d\n",
MR_SELF_THREAD_ID, cur->MR_ctxt_resume_owner_engine);
}
#endif
if (cur->MR_ctxt_resume_owner_engine == engine_id) {
/*
** This context prefers to be ran on this engine.
*/
preferred_context = cur;
preferred_context_prev = prev;
} else if (preferred_context == NULL) {
/*
** There is no preferred context yet, and this context is okay.
*/
preferred_context = cur;
preferred_context_prev = prev;
}
}
prev = cur;
cur = cur->MR_ctxt_next;
}
if (preferred_context != NULL) {
if (preferred_context_prev != NULL) {
preferred_context_prev->MR_ctxt_next =
preferred_context->MR_ctxt_next;
} else {
MR_runqueue_head = preferred_context->MR_ctxt_next;
}
if (MR_runqueue_tail == preferred_context) {
MR_runqueue_tail = preferred_context_prev;
}
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Will run context %p\n",
MR_SELF_THREAD_ID, preferred_context);
}
#endif
} else {
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld No suitable context to run\n",
MR_SELF_THREAD_ID);
}
#endif
}
return preferred_context;
}
static MR_bool
MR_attempt_steal_spark(MR_Spark *spark)
{
int i;
int offset;
MR_SparkDeque *victim;
int steal_result;
MR_bool result = MR_FALSE;
offset = MR_ENGINE(MR_eng_victim_counter);
for (i = 0; i < MR_num_threads; i++) {
victim = MR_spark_deques[(i + offset) % MR_num_threads];
if (victim != NULL) {
steal_result = MR_wsdeque_steal_top(victim, spark);
/*
** If we lost a race to steal the spark, we continue to attempt
** to steal the spark until we succeed (steal_result == 1) or
** until the deque is empty (steal_result == 0)
*/
while (steal_result == -1) {
MR_ATOMIC_PAUSE;
steal_result = MR_wsdeque_steal_top(victim, spark);
}
if (steal_result == 1) {
/* Steal successful. */
result = MR_TRUE;
break;
}
}
}
MR_ENGINE(MR_eng_victim_counter) = (i % MR_num_threads);
return result;
}
static void
MR_milliseconds_from_now(struct timespec *timeout, unsigned int msecs)
{
#if defined(MR_HAVE_GETTIMEOFDAY)
const long NANOSEC_PER_SEC = 1000000000L;
struct timeval now;
MR_int_least64_t nanosecs;
gettimeofday(&now, NULL);
timeout->tv_sec = now.tv_sec;
nanosecs = ((MR_int_least64_t) (now.tv_usec + (msecs * 1000))) * 1000L;
if (nanosecs >= NANOSEC_PER_SEC) {
timeout->tv_sec++;
nanosecs %= NANOSEC_PER_SEC;
}
timeout->tv_nsec = (long) nanosecs;
#elif defined(MR_WIN32)
const long NANOSEC_PER_SEC = 1000000000L;
const long NANOSEC_PER_MILLISEC = 1000000L;
struct _timeb now;
MR_int_least64_t nanosecs;
_ftime(&now);
timeout->tv_sec = now.time;
nanosecs = ((MR_int_least64_t) (msecs + now.millitm)) *
NANOSEC_PER_MILLISEC;
if (nanosecs >= NANOSEC_PER_SEC) {
timeout->tv_sec++;
nanosecs %= NANOSEC_PER_SEC;
}
timeout->tv_nsec = (long) nanosecs;
#else
#error Missing definition of MR_milliseconds_from_now.
#endif
}
#endif /* MR_LL_PARALLEL_CONJ */
void
MR_flounder(void)
{
MR_fatal_error("computation floundered");
}
void
MR_sched_yield(void)
{
#if defined(MR_HAVE_SCHED_YIELD)
sched_yield();
#elif defined(MR_CAN_DO_PENDING_IO)
struct timeval timeout = {0, 1};
select(0, NULL, NULL, NULL, &timeout);
#endif
}
/*
** Check to see if any contexts that blocked on IO have become runnable.
** Return the number of contexts that are still blocked.
** The parameter specifies whether or not the call to select should block
** or not.
*/
static int
MR_check_pending_contexts(MR_bool block)
{
#ifdef MR_CAN_DO_PENDING_IO
int err;
int max_id;
int n_ids;
fd_set rd_set0;
fd_set wr_set0;
fd_set ex_set0;
fd_set rd_set;
fd_set wr_set;
fd_set ex_set;
struct timeval timeout;
MR_PendingContext *pctxt;
if (MR_pending_contexts == NULL) {
return 0;
}
MR_fd_zero(&rd_set0);
MR_fd_zero(&wr_set0);
MR_fd_zero(&ex_set0);
max_id = -1;
for (pctxt = MR_pending_contexts ; pctxt ; pctxt = pctxt -> next) {
if (pctxt->waiting_mode & MR_PENDING_READ) {
if (max_id > pctxt->fd) {
max_id = pctxt->fd;
}
FD_SET(pctxt->fd, &rd_set0);
}
if (pctxt->waiting_mode & MR_PENDING_WRITE) {
if (max_id > pctxt->fd) {
max_id = pctxt->fd;
}
FD_SET(pctxt->fd, &wr_set0);
}
if (pctxt->waiting_mode & MR_PENDING_EXEC) {
if (max_id > pctxt->fd) {
max_id = pctxt->fd;
}
FD_SET(pctxt->fd, &ex_set0);
}
}
max_id++;
if (max_id == 0) {
MR_fatal_error("no fd's set!");
}
if (block) {
do {
rd_set = rd_set0;
wr_set = wr_set0;
ex_set = ex_set0;
err = select(max_id, &rd_set, &wr_set, &ex_set, NULL);
} while (err == -1 && MR_is_eintr(errno));
} else {
do {
rd_set = rd_set0;
wr_set = wr_set0;
ex_set = ex_set0;
timeout.tv_sec = 0;
timeout.tv_usec = 0;
err = select(max_id, &rd_set, &wr_set, &ex_set, &timeout);
} while (err == -1 && MR_is_eintr(errno));
}
if (err < 0) {
MR_fatal_error("select failed!");
}
n_ids = 0;
for (pctxt = MR_pending_contexts; pctxt; pctxt = pctxt -> next) {
n_ids++;
if ( ((pctxt->waiting_mode & MR_PENDING_READ)
&& FD_ISSET(pctxt->fd, &rd_set))
|| ((pctxt->waiting_mode & MR_PENDING_WRITE)
&& FD_ISSET(pctxt->fd, &wr_set))
|| ((pctxt->waiting_mode & MR_PENDING_EXEC)
&& FD_ISSET(pctxt->fd, &ex_set))
)
{
MR_schedule_context(pctxt->context);
}
}
return n_ids;
#else /* !MR_CAN_DO_PENDING_IO */
MR_fatal_error("select() unavailable!");
#endif
}
void
MR_schedule_context(MR_Context *ctxt)
{
#ifdef MR_LL_PARALLEL_CONJ
MR_EngineId engine_id;
union MR_engine_wake_action_data wake_action_data;
wake_action_data.MR_ewa_context = ctxt;
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
MR_threadscope_post_context_runnable(ctxt);
#endif
/*
** Try to give this context straight to the engine that would execute it.
*/
engine_id = ctxt->MR_ctxt_resume_owner_engine;
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Scheduling context %p desired engine: %d\n",
MR_SELF_THREAD_ID, ctxt, engine_id);
}
#endif
if (ctxt->MR_ctxt_resume_engine_required == MR_TRUE) {
/*
** Only engine_id may execute this context, attempt to wake it.
**
** Note that there is a race condition here. If the engine that can
** run this context is working, then try_wake_engine() will fail, if
** it then becomes idle and checks the run queue before we acquire
** the run queue lock below then it can go to sleep and won't be
** notified that there is a context to execute. The context will be
** placed on the run queue awaiting the engine. If the context can
** only be executed by a single engine, then that engine will only
** check the run queue if it first executes a spark, causing it to
** call MR_do_idle after completing the spark.
**
** This is only a problem for contexts that can only be executed on
** a single engine. In other causes this engine is guaranteed to
** eventually call MR_do_idle and execute the context. Potentially
** causing a loss of parallelism but not a deadlock.
**
** We can fix this race by adding an extra message, which we
** tentatively call MR_ENGINE_ACTION_CONTEXT_ADVICE, which does not
** contain a context but tells an engine that one is available.
** After placing a context on the run queue we can deliver this
** message to an idle engine that should check the run queue if it
** hasn't already. We must also guarantee that an engine checks if
** it has any notifications before going into the sleeping state.
**
** I have a workspace in which I fix these problems, however it is
** buggy in other ways so I cannot commit it yet. For now I'm
** documenting it in this comment.
**
** See runtime/design/par_engine_state.{txt,dot} for details of the
** proposed changes to the engine notification code. Although the
** proposed changes in these files are much more complex than is
** strictly needed, we believe that they avoid other problems.
*/
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Context _must_ run on this engine\n",
MR_SELF_THREAD_ID);
}
#endif
/*
** There is a bug on this line, we should never give a context
** notification to an idle engine as the notification can be lost if
** the engine writes-over its own state and then a later
** notification is passed to the engine.
**
** However I don't want to fix it as fixing it may make the window
** for the race condition documented above wider.
*/
if (try_wake_engine(engine_id, MR_ENGINE_ACTION_CONTEXT,
&wake_action_data, ENGINE_STATE_IDLE | ENGINE_STATE_SLEEPING))
{
/*
** We have successfully given the context to the correct engine.
*/
return;
}
} else {
/*
** If there is some idle engine, try to wake it up, starting with the
** preferred engine.
*/
if (MR_num_idle_engines > 0) {
if (MR_try_wake_an_engine(engine_id, MR_ENGINE_ACTION_CONTEXT,
&wake_action_data, NULL))
{
/*
** The context has been given to an engine.
*/
return;
}
}
}
#endif /* MR_LL_PARALLEL_CONJ */
MR_LOCK(&MR_runqueue_lock, "schedule_context");
ctxt->MR_ctxt_next = NULL;
if (MR_runqueue_tail) {
MR_runqueue_tail->MR_ctxt_next = ctxt;
MR_runqueue_tail = ctxt;
} else {
MR_runqueue_head = ctxt;
MR_runqueue_tail = ctxt;
}
MR_UNLOCK(&MR_runqueue_lock, "schedule_context");
}
#ifdef MR_LL_PARALLEL_CONJ
/*
** Try to wake an engine, starting at the preferred engine.
*/
MR_bool
MR_try_wake_an_engine(MR_EngineId preferred_engine, int action,
union MR_engine_wake_action_data *action_data, MR_EngineId *target_eng)
{
MR_EngineId current_engine;
int i = 0;
int state;
MR_bool result;
/*
** Right now this algorithm is naive, it searches from the preferred engine
** around the loop until it finds an engine.
*/
for (i = 0; i < MR_num_threads; i++) {
current_engine = (i + preferred_engine) % MR_num_threads;
if (current_engine == MR_ENGINE(MR_eng_id)) {
/*
** Don't post superfluous events to ourself.
*/
continue;
}
state = engine_sleep_sync_data[current_engine].d.es_state;
if (state == ENGINE_STATE_SLEEPING) {
result = try_wake_engine(current_engine, action, action_data,
ENGINE_STATE_SLEEPING);
if (result) {
if (target_eng) {
*target_eng = current_engine;
}
return MR_TRUE;
}
}
}
return MR_FALSE;
}
static MR_bool
try_wake_engine(MR_EngineId engine_id, int action,
union MR_engine_wake_action_data *action_data, unsigned states)
{
MR_bool success = MR_FALSE;
engine_sleep_sync *esync = &(engine_sleep_sync_data[engine_id]);
/*
** This engine is probably in the state our caller checked that it was in.
** Wait on the semaphore then re-check the state to be sure.
*/
MR_LOCK(&(esync->d.es_wake_lock), "try_wake_engine, wake_lock");
if (esync->d.es_state & states) {
MR_atomic_dec_int(&MR_num_idle_engines);
/*
** We now KNOW that the engine is in one of the correct states.
**
** We tell the engine what to do, and tell others that we have woken it
** before actually waking it.
*/
esync->d.es_action = action;
if (action_data) {
esync->d.es_action_data = *action_data;
}
esync->d.es_state = ENGINE_STATE_WOKEN;
MR_CPU_SFENCE;
MR_SEM_POST(&(esync->d.es_sleep_semaphore),
"try_wake_engine sleep_sem");
success = MR_TRUE;
}
MR_UNLOCK(&(esync->d.es_wake_lock), "try_wake_engine wake_lock");
return success;
}
void
MR_shutdown_all_engines(void)
{
int i;
for (i = 0; i < MR_num_threads; i++) {
if (i == MR_ENGINE(MR_eng_id)) {
continue;
}
try_wake_engine(i, MR_ENGINE_ACTION_SHUTDOWN, NULL,
ENGINE_STATE_ALL);
}
for (i = 0; i < (MR_num_threads - 1); i++) {
MR_SEM_WAIT(&shutdown_semaphore, "MR_shutdown_all_engines");
}
}
#endif /* MR_LL_PARALLEL_CONJ */
#ifndef MR_HIGHLEVEL_CODE
/****************************************************************************
**
** Parallel runtime idle loop.
**
** This also contains code to run the next runnable context for non-parallel
** low level C grades.
**
*/
/*
** The run queue used to include timing code. It has been removed and may be
** added in the future.
*/
MR_define_extern_entry(MR_do_idle);
#ifdef MR_THREAD_SAFE
MR_define_extern_entry(MR_do_idle_clean_context);
MR_define_extern_entry(MR_do_idle_dirty_context);
MR_define_extern_entry(MR_do_sleep);
static MR_Code*
do_get_context(void);
static MR_Code*
do_local_spark(MR_Code *join_label);
static MR_Code*
do_work_steal(void);
static void
save_dirty_context(MR_Code *join_label);
/*
** Prepare the engine to execute a spark. Only call this if either:
** 1) the engine does not have a context.
** 2) the engine's context is free for use with the spark.
*/
static void
prepare_engine_for_spark(volatile MR_Spark *spark);
/*
** Prepare the engine to execute a context. This loads the context into the
** engine after discarding any existing context. All the caller need do is
** jump to the resume/start point.
*/
static void
prepare_engine_for_context(MR_Context *context);
/*
** Advertise that the engine is looking for work after being in the
** working state. (Do not use this call when waking from sleep).
*/
static void
advertise_engine_state_idle(void);
/*
** Advertise that the engine will begin working.
*/
static void
advertise_engine_state_working(void);
#endif
MR_BEGIN_MODULE(scheduler_module_idle)
MR_init_entry_an(MR_do_idle);
MR_BEGIN_CODE
MR_define_entry(MR_do_idle);
#ifdef MR_THREAD_SAFE
{
MR_Code *jump_target;
/*
** Try to get a context.
*/
advertise_engine_state_idle();
jump_target = do_get_context();
if (jump_target != NULL) {
advertise_engine_state_working();
MR_GOTO(jump_target);
}
jump_target = do_local_spark(NULL);
if (jump_target != NULL) {
advertise_engine_state_working();
MR_GOTO(jump_target);
}
jump_target = do_work_steal();
if (jump_target != NULL) {
advertise_engine_state_working();
MR_GOTO(jump_target);
}
MR_GOTO(MR_ENTRY(MR_do_sleep));
}
#else /* !MR_THREAD_SAFE */
{
/*
** When an engine becomes idle in a non parallel grade, it simply picks up
** another context.
*/
if (MR_runqueue_head == NULL && MR_pending_contexts == NULL) {
MR_fatal_error("empty runqueue!");
}
while (MR_runqueue_head == NULL) {
MR_check_pending_contexts(MR_TRUE); /* block */
}
MR_ENGINE(MR_eng_this_context) = MR_runqueue_head;
MR_runqueue_head = MR_runqueue_head->MR_ctxt_next;
if (MR_runqueue_head == NULL) {
MR_runqueue_tail = NULL;
}
MR_load_context(MR_ENGINE(MR_eng_this_context));
MR_GOTO(MR_ENGINE(MR_eng_this_context)->MR_ctxt_resume);
}
#endif /* !MR_THREAD_SAFE */
MR_END_MODULE
#ifdef MR_THREAD_SAFE
MR_BEGIN_MODULE(scheduler_module_idle_clean_context)
MR_init_entry_an(MR_do_idle_clean_context);
MR_BEGIN_CODE
MR_define_entry(MR_do_idle_clean_context);
{
#ifdef MR_THREADSCOPE
MR_threadscope_post_stop_context(MR_TS_STOP_REASON_FINISHED);
#endif
advertise_engine_state_idle();
MR_Code *jump_target;
jump_target = do_get_context();
if (jump_target != NULL) {
advertise_engine_state_working();
MR_GOTO(jump_target);
}
jump_target = do_local_spark(NULL);
if (jump_target != NULL) {
advertise_engine_state_working();
MR_GOTO(jump_target);
}
jump_target = do_work_steal();
if (jump_target != NULL) {
advertise_engine_state_working();
MR_GOTO(jump_target);
}
MR_GOTO(MR_ENTRY(MR_do_sleep));
}
MR_END_MODULE
#endif /* MR_THREAD_SAFE */
#ifdef MR_THREAD_SAFE
MR_BEGIN_MODULE(scheduler_module_idle_dirty_context)
MR_init_entry_an(MR_do_idle_dirty_context);
MR_BEGIN_CODE
MR_define_entry(MR_do_idle_dirty_context);
{
MR_Code *join_label = (MR_Code*)MR_r1;
MR_Code *jump_target;
/*
** We check for local sparks first. If there is a local spark that is
** compatible then execute it, it is 'left most' next to the computation
** that this engine has just finished, and could be more optimal than
** any suspended context. Let another engine pay the cost of the
** context switch.
**
** If there was an incompatible local spark then it may still be
** executed after the jump to MR_do_idle below.
*/
jump_target = do_local_spark(join_label);
if (jump_target != NULL) {
MR_GOTO(jump_target);
}
/*
** Save our context and then look for work as per normal.
*/
#ifdef MR_THREADSCOPE
MR_threadscope_post_stop_context(MR_TS_STOP_REASON_BLOCKED);
#endif
save_dirty_context(join_label);
MR_ENGINE(MR_eng_this_context) = NULL;
MR_GOTO(MR_ENTRY(MR_do_idle));
}
MR_END_MODULE
/*
** Put the engine to sleep since there's no work to do.
**
** This call does not return.
**
** REQUIREMENT: Only call this with either no context or a clean context.
** REQUIREMENT: This must be called from the same C and Mercury stack depths as
** the call into the idle loop.
*/
MR_BEGIN_MODULE(scheduler_module_idle_sleep)
MR_init_entry_an(MR_do_sleep);
MR_BEGIN_CODE
MR_define_entry(MR_do_sleep);
{
MR_EngineId engine_id = MR_ENGINE(MR_eng_id);
unsigned action;
int result;
struct timespec ts;
struct timeval tv;
MR_Code *jump_target;
while (1) {
engine_sleep_sync_data[engine_id].d.es_state = ENGINE_STATE_SLEEPING;
MR_CPU_SFENCE;
#ifdef MR_THREADSCOPE
MR_threadscope_post_engine_sleeping();
#endif
#if defined(MR_HAVE_GETTIMEOFDAY) && defined(MR_HAVE_SEMAPHORE_H)
gettimeofday(&tv, NULL);
/* Sleep for 2ms */
tv.tv_usec += 2000;
if (tv.tv_usec >= 1000000) {
tv.tv_usec = tv.tv_sec % 1000000;
tv.tv_sec += 1;
}
ts.tv_sec = tv.tv_sec;
ts.tv_nsec = tv.tv_usec * 1000;
result = sem_timedwait(
&(engine_sleep_sync_data[engine_id].d.es_sleep_semaphore),
&ts);
#else
MR_fatal_error(
"low-level parallel grades need gettimeofday() and "
"sem_timedwait()\n");
#endif
if (0 == result) {
MR_CPU_LFENCE;
action = engine_sleep_sync_data[engine_id].d.es_action;
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Engine %d is awake and will do action %d\n",
MR_SELF_THREAD_ID, engine_id, action);
}
#endif
switch(action) {
case MR_ENGINE_ACTION_SHUTDOWN:
/*
** The primordial thread has the responsibility of cleaning
** up the Mercury runtime. It cannot exit by this route.
*/
assert(engine_id != 0);
MR_atomic_dec_int(&MR_num_idle_engines);
MR_destroy_thread(MR_cur_engine());
MR_SEM_POST(&shutdown_semaphore,
"MR_do_sleep shutdown_sem");
pthread_exit(0);
break;
case MR_ENGINE_ACTION_WORKSTEAL:
MR_ENGINE(MR_eng_victim_counter) =
engine_sleep_sync_data[engine_id].d.es_action_data.
MR_ewa_worksteal_engine;
jump_target = do_work_steal();
if (jump_target != NULL) {
engine_sleep_sync_data[engine_id].d.es_state =
ENGINE_STATE_WORKING;
MR_GOTO(jump_target);
}
jump_target = do_get_context();
if (jump_target != NULL) {
engine_sleep_sync_data[engine_id].d.es_state =
ENGINE_STATE_WORKING;
MR_GOTO(jump_target);
}
break;
case MR_ENGINE_ACTION_CONTEXT:
{
MR_Context *context;
MR_Code *resume_point;
engine_sleep_sync_data[engine_id].d.es_state =
ENGINE_STATE_WORKING;
context = engine_sleep_sync_data[engine_id].d.
es_action_data.MR_ewa_context;
prepare_engine_for_context(context);
#ifdef MR_DEBUG_STACK_SEGMENTS
MR_debug_log_message("resuming old context: %p",
context);
#endif
resume_point = (MR_Code*)(context->MR_ctxt_resume);
context->MR_ctxt_resume = NULL;
MR_GOTO(resume_point);
}
break;
case MR_ENGINE_ACTION_NONE:
default:
jump_target = do_get_context();
if (jump_target != NULL) {
engine_sleep_sync_data[engine_id].d.es_state =
ENGINE_STATE_WORKING;
MR_GOTO(jump_target);
}
jump_target = do_work_steal();
if (jump_target != NULL) {
engine_sleep_sync_data[engine_id].d.es_state =
ENGINE_STATE_WORKING;
MR_GOTO(jump_target);
}
break;
}
} else {
/*
** Sem_wait reported an error.
*/
switch (errno) {
case EINTR:
/*
** An interrupt woke the engine, go back to sleep.
*/
break;
case ETIMEDOUT:
/*
** A wait timed out, check for any sparks.
*/
jump_target = do_work_steal();
if (jump_target != NULL) {
advertise_engine_state_working();
MR_GOTO(jump_target);
}
break;
default:
perror("sem_timedwait");
abort();
}
}
}
}
MR_END_MODULE
#endif
#ifdef MR_THREAD_SAFE
static MR_Code*
do_get_context(void)
{
MR_Context *ready_context;
MR_Code *resume_point;
/*
** Look for a runnable context and execute it. If there was no runnable
** context, then proceed to MR_do_runnext_local.
*/
#ifdef MR_THREADSCOPE
MR_threadscope_post_looking_for_global_context();
#endif
if (MR_runqueue_head != NULL) {
MR_LOCK(&MR_runqueue_lock, "do_get_context (i)");
ready_context = MR_find_ready_context();
MR_UNLOCK(&MR_runqueue_lock, "do_get_context (ii)");
if (ready_context != NULL) {
prepare_engine_for_context(ready_context);
#ifdef MR_DEBUG_STACK_SEGMENTS
MR_debug_log_message("resuming old context: %p", ready_context);
#endif
resume_point = (MR_Code*)(ready_context->MR_ctxt_resume);
ready_context->MR_ctxt_resume = NULL;
return resume_point;
}
}
return NULL;
}
static void
prepare_engine_for_context(MR_Context *context) {
/*
** Discard whatever unused context we may have, and switch to the new one.
*/
if (MR_ENGINE(MR_eng_this_context) != NULL) {
#ifdef MR_DEBUG_STACK_SEGMENTS
MR_debug_log_message("destroying old context %p",
MR_ENGINE(MR_eng_this_context));
#endif
/*
** Saving the context is important. Details such as the current
** stack pointer must be reset before the context is released.
*/
MR_save_context(MR_ENGINE(MR_eng_this_context));
MR_release_context(MR_ENGINE(MR_eng_this_context));
}
MR_ENGINE(MR_eng_this_context) = context;
MR_load_context(context);
#ifdef MR_THREADSCOPE
MR_threadscope_post_run_context();
#endif
}
static void
prepare_engine_for_spark(volatile MR_Spark *spark)
{
MR_Context *this_context = MR_ENGINE(MR_eng_this_context);
if (this_context == NULL) {
/*
** Get a new context
*/
#ifdef MR_DEBUG_CONTEXT_CREATION_SPEED
MR_debug_log_message("Need a new context.");
#endif
MR_ENGINE(MR_eng_this_context) = MR_create_context("from spark",
MR_CONTEXT_SIZE_FOR_SPARK, NULL);
#ifdef MR_THREADSCOPE
MR_threadscope_post_create_context_for_spark(
MR_ENGINE(MR_eng_this_context));
#endif
/*
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
if (MR_profile_parallel_execution) {
MR_atomic_inc_int(
&MR_profile_parallel_contexts_created_for_sparks);
}
#endif
*/
MR_load_context(MR_ENGINE(MR_eng_this_context));
#ifdef MR_DEBUG_STACK_SEGMENTS
MR_debug_log_message("created new context for spark: %p",
MR_ENGINE(MR_eng_this_context));
#endif
} else {
#ifdef MR_THREADSCOPE
MR_Unsigned old_id;
old_id = MR_ENGINE(MR_eng_this_context)->MR_ctxt_num_id;
MR_ENGINE(MR_eng_this_context)->MR_ctxt_num_id = allocate_context_id();
MR_threadscope_post_reuse_context(MR_ENGINE(MR_eng_this_context),
old_id);
#endif
}
#ifdef MR_THREADSCOPE
MR_threadscope_post_run_context();
#endif
/*
** At this point we have a context, either a dirty context that is
** compatible, or a clean one.
*/
MR_parent_sp = spark->MR_spark_sync_term->MR_st_parent_sp;
MR_SET_THREAD_LOCAL_MUTABLES(spark->MR_spark_thread_local_mutables);
MR_assert(MR_parent_sp);
MR_assert(spark->MR_spark_sync_term->MR_st_count > 0);
}
static MR_Code*
do_local_spark(MR_Code *join_label)
{
volatile MR_Spark *spark;
MR_Context *this_context = MR_ENGINE(MR_eng_this_context);
#ifdef MR_THREADSCOPE
MR_threadscope_post_looking_for_local_spark();
#endif
spark = MR_wsdeque_pop_bottom(&MR_ENGINE(MR_eng_spark_deque));
if (NULL == spark) {
return NULL;
}
/*
** The current context may be dirty and incompatible with this spark, if
** so we put the spark back ondo the deque. This test is only
** applicable when running a local spark.
**
** Our caller will then save the context and look for a different
** context to run, if it cannot find a context then it will call this
** function again to run the incompatible spark, allocating a new context.
*/
if ((this_context != NULL) &&
(join_label != NULL) &&
(spark->MR_spark_sync_term->MR_st_orig_context != this_context))
{
/* The cast discards the volatile qualifier, which is okay */
MR_wsdeque_putback_bottom(&MR_ENGINE(MR_eng_spark_deque),
(MR_Spark*) spark);
return NULL;
}
#ifdef MR_THREADSCOPE
MR_threadscope_post_run_spark(spark->MR_spark_id);
#endif
prepare_engine_for_spark(spark);
return spark->MR_spark_resume;
}
static MR_Code*
do_work_steal(void)
{
MR_Spark spark;
#ifdef MR_THREADSCOPE
MR_threadscope_post_work_stealing();
#endif
/*
** A context may be created to execute a spark, so only attempt to
** steal sparks if doing so would not exceed the limit of outstanding
** contexts.
*/
if ((MR_ENGINE(MR_eng_this_context) != NULL) ||
(MR_num_outstanding_contexts <= MR_max_outstanding_contexts)) {
/* Attempt to steal a spark */
if (MR_attempt_steal_spark(&spark)) {
#ifdef MR_THREADSCOPE
MR_threadscope_post_steal_spark(spark.MR_spark_id);
#endif
prepare_engine_for_spark(&spark);
return spark.MR_spark_resume;
}
}
return NULL;
}
static void
save_dirty_context(MR_Code *join_label) {
MR_Context *this_context = MR_ENGINE(MR_eng_this_context);
#ifdef MR_THREADSCOPE
MR_threadscope_post_stop_context(MR_TS_STOP_REASON_BLOCKED);
#endif
this_context->MR_ctxt_resume_owner_engine = MR_ENGINE(MR_eng_id);
MR_save_context(this_context);
/*
** Make sure the context gets saved before we set the join label,
** use a memory barrier.
*/
MR_CPU_SFENCE;
this_context->MR_ctxt_resume = join_label;
MR_ENGINE(MR_eng_this_context) = NULL;
}
static void
advertise_engine_state_idle(void)
{
engine_sleep_sync_data[MR_ENGINE(MR_eng_id)].d.es_state =
ENGINE_STATE_IDLE;
MR_CPU_SFENCE;
MR_atomic_inc_int(&MR_num_idle_engines);
}
static void
advertise_engine_state_working(void)
{
MR_atomic_dec_int(&MR_num_idle_engines);
MR_CPU_SFENCE;
engine_sleep_sync_data[MR_ENGINE(MR_eng_id)].d.es_state =
ENGINE_STATE_WORKING;
}
#endif /* MR_THREAD_SAFE */
#endif /* !MR_HIGHLEVEL_CODE */
#ifdef MR_LL_PARALLEL_CONJ
MR_Code*
MR_do_join_and_continue(MR_SyncTerm *jnc_st, MR_Code *join_label)
{
MR_bool jnc_last;
MR_Context *this_context = MR_ENGINE(MR_eng_this_context);
#ifdef MR_THREADSCOPE
MR_threadscope_post_end_par_conjunct((MR_Word*)jnc_st);
#endif
/*
** Atomically decrement and fetch the number of conjuncts yet to complete.
** If we are the last conjunct to complete (the parallel conjunction is
** finished) then jnc_last will be true.
*/
/*
** XXX: We should take the current TSC time here and use it to post the
** various 'context stopped' threadscope events. This profile will be more
** accurate.
*/
jnc_last = MR_atomic_dec_and_is_zero_uint(&(jnc_st->MR_st_count));
if (jnc_last) {
/*
** All the conjuncts have finished,
*/
if (this_context != jnc_st->MR_st_orig_context) {
#ifdef MR_THREADSCOPE
MR_threadscope_post_stop_context(MR_TS_STOP_REASON_FINISHED);
#endif
/*
** This context didn't originate this parallel conjunction and
** we are the last branch to finish. The originating context should
** be suspended waiting for us to finish, we should run it using
** the current engine.
**
** We could be racing with the original context, in which case we
** have to make sure that it is ready to be scheduled before we
** schedule it. It will set its resume point to join_label to
** indicate that it is ready.
*/
while (jnc_st->MR_st_orig_context->MR_ctxt_resume != join_label) {
/* XXX: Need to configure using sched_yeild or spin waiting */
MR_ATOMIC_PAUSE;
}
#ifdef MR_THREADSCOPE
MR_threadscope_post_context_runnable(jnc_st->MR_st_orig_context);
#endif
prepare_engine_for_context(jnc_st->MR_st_orig_context);
/*
** This field must be reset to NULL
*/
jnc_st->MR_st_orig_context->MR_ctxt_resume = NULL;
}
/*
** Continue the parallel conjunction.
*/
return join_label;
} else {
if (this_context == jnc_st->MR_st_orig_context) {
MR_r1 = (MR_Word)join_label;
return MR_ENTRY(MR_do_idle_dirty_context);
} else {
/*
** This engine and context should look for other work.
*/
return MR_ENTRY(MR_do_idle_clean_context);
}
}
}
#endif
#ifdef MR_LL_PARALLEL_CONJ
/*
** Debugging functions for runtime granularity control.
*/
#ifdef MR_DEBUG_RUNTIME_GRANULARITY_CONTROL
#define MR_PAR_COND_STATS_FILENAME "par_cond_stats.log"
static FILE * volatile MR_par_cond_stats_file = NULL;
static volatile MR_Unsigned MR_par_cond_stats_last;
static volatile MR_Unsigned MR_par_cond_stats_last_count;
void MR_record_conditional_parallelism_decision(MR_Unsigned decision)
{
MR_LOCK(&MR_par_cond_stats_lock,
"record_conditional_parallelism_decision");
if (MR_par_cond_stats_file == NULL) {
MR_par_cond_stats_file = fopen(MR_PAR_COND_STATS_FILENAME, "w");
MR_par_cond_stats_last = decision;
MR_par_cond_stats_last_count = 1;
} else {
if (decision == MR_par_cond_stats_last) {
MR_par_cond_stats_last_count++;
} else {
fprintf(MR_par_cond_stats_file, "%d %d\n", MR_par_cond_stats_last,
MR_par_cond_stats_last_count);
MR_par_cond_stats_last = decision;
MR_par_cond_stats_last_count = 1;
}
}
MR_UNLOCK(&MR_par_cond_stats_lock,
"record_conditional_parallelism_decision");
}
void MR_write_out_conditional_parallelism_log(void)
{
MR_LOCK(&MR_par_cond_stats_lock,
"write_out_conditional_parallelism_log");
if (MR_par_cond_stats_file != NULL) {
fprintf(MR_par_cond_stats_file, "%d %d\n",
MR_par_cond_stats_last, MR_par_cond_stats_last_count);
fclose(MR_par_cond_stats_file);
MR_par_cond_stats_file = NULL;
}
MR_UNLOCK(&MR_par_cond_stats_lock,
"write_out_conditional_parallelism_log");
}
#endif /* MR_DEBUG_RUNTIME_GRANULARITY_CONTROL */
#endif /* MR_LL_PARALLEL_CONJ */
/* forward decls to suppress gcc warnings */
void mercury_sys_init_scheduler_wrapper_init(void);
void mercury_sys_init_scheduler_wrapper_init_type_tables(void);
#ifdef MR_DEEP_PROFILING
void mercury_sys_init_scheduler_wrapper_write_out_proc_statics(FILE *fp);
#endif
void mercury_sys_init_scheduler_wrapper_init(void)
{
#ifndef MR_HIGHLEVEL_CODE
scheduler_module_idle();
#ifdef MR_THREAD_SAFE
scheduler_module_idle_clean_context();
scheduler_module_idle_dirty_context();
scheduler_module_idle_sleep();
#endif
#endif
}
void mercury_sys_init_scheduler_wrapper_init_type_tables(void)
{
/* no types to register */
}
#ifdef MR_DEEP_PROFILING
void mercury_sys_init_scheduler_wrapper_write_out_proc_statics(FILE *fp)
{
/* no proc_statics to write out */
}
#endif
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