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a4b26739ba6671bab9ee3540858a86ebe6f7e996
mercury/runtime/mercury_context.c
Peter Wang a4b26739ba Reset es_action field when idle ws engine receives a notification. 
In MR_do_idle_worksteal, reset the engine's es_action field to
MR_ENGINE_ACTION_NONE before performing the notified action.
This mirrors the behaviour in MR_do_sleep.

Fixes the assertion failure in Mantis bug #461: when an engine is
shut down, MR_verify_final_engine_sleep_sync checks that the engine's
es_action field is MR_ENGINE_ACTION_NONE.

runtime/mercury_context.c:
    As above.

NEWS:
    Announce change.
2020-04-20 12:41:45 +10:00

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// vim: ts=4 sw=4 expandtab ft=c
// Copyright (C) 1995-2007, 2009-2011 The University of Melbourne.
// Copyright (C) 2014, 2016-2018 The Mercury team.
// This file is distributed under the terms specified in COPYING.LIB.
// mercury_context.c - handles multithreading stuff.
/*
INIT mercury_sys_init_scheduler_wrapper
ENDINIT
*/
#ifndef _GNU_SOURCE
// This must be defined prior to including <sched.h> for sched_setaffinity,
// etc.
#define _GNU_SOURCE
#endif
#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
#if defined(MR_THREAD_SAFE) && defined(MR_HAVE_HWLOC)
#include <hwloc.h>
#endif
#if defined(MR_HAVE_SCHED_H)
#include <sched.h>
#endif
#if defined(MR_HAVE_SCHED_GETAFFINITY) && \
defined(MR_HAVE_SCHED_SETAFFINITY) && \
defined(MR_HAVE_SCHED_CPUSET_MACROS)
#define MR_HAVE_LINUX_CPU_AFFINITY_API 1
#endif
#ifdef MR_MINGW
#include <sys/time.h> // for gettimeofday()
#endif
#ifdef MR_WIN32
#include <sys/timeb.h> // for _ftime()
#endif
#ifdef MR_WIN32_GETSYSTEMINFO
#include "mercury_windows.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
#include "mercury_runtime_util.h"
#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);
// Engine states and notifications
// -------------------------------
//
// An engine may be in one of the following states, see the es_state field
// engine_sleep_sync_i
//
// working The engine has work to do and is working on it.
// The engine will not check for notifications, all
// notifications will be ignored.
//
// idle The engine finished its work and is looking for
// more work. It is looking for a context to resume or a local
// spark. If found, the engine will move to the working state,
// if not, it will check for notifications and if there are
// none it moves to the stealing state. Only notify an idle
// engine with notifications that may be ignored.
//
// stealing The engine is now attempting to work steal. It has now
// incremented the idle engine count to make it easier to
// receive notifications. If it finds a spark it will decrement
// the count and execute the spark. Otherwise it checks for
// notifications and moves to the sleeping state. This state
// is similar to idle but separate as it allows another engine
// to understand if this engine has modified the idle engine
// count (which we don't want to do in the idle state as that
// will often find a local spark to execute).
//
// sleeping The engine has committed to going to sleep, to wake it up
// one must post to its sleep semaphore ensuring that it does
// not sleep. Any notification can be sent at this stage as
// all will be acted upon, including the context notification
// which cannot be dropped.
//
// notified
// The engine has received a notification, it cannot receive
// another notification now. This state is initiated by the
// notifier, and therefore is done with either a compare and
// swap or a lock depending on the state of the engine. See
// try_wake_engine and try_notify_engine. Upon receiving the
// notification the engine will set its new status
// appropriately.
//
// More information about these states including which transitions are legal
// can be found in notes/par_engine_state.{txt,dot}
// Busy isn't a normal state, but it's used with the CAS code to make some
// operations atomic.
#define ENGINE_STATE_BUSY 0x0000
#define ENGINE_STATE_WORKING 0x0001
#define ENGINE_STATE_IDLE 0x0002
#define ENGINE_STATE_STEALING 0x0004
#define ENGINE_STATE_SLEEPING 0x0008
#define ENGINE_STATE_NOTIFIED 0x0010
#define ENGINE_STATE_ALL 0xFFFF
struct engine_sleep_sync_i {
MercurySem es_sleep_semaphore;
MercuryLock es_wake_lock;
volatile MR_Unsigned es_state;
volatile unsigned es_action;
volatile union MR_engine_wake_action_data es_action_data;
};
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;
static engine_sleep_sync *
get_engine_sleep_sync(MR_EngineId i)
{
MR_assert(i < MR_max_engines);
return &engine_sleep_sync_data[i];
}
#endif // MR_LL_PARALLEL_CONJ
// The run queue is protected with MR_runqueue_lock.
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
#ifdef MR_THREAD_SAFE
// The detected number of processors available to this process,
// or zero if not (yet) determined.
static unsigned MR_num_processors_detected;
// Structures representing the processors available to this process.
// These are required for thread pinning but also used to count
// MR_num_processors_detected.
#if defined(MR_HAVE_HWLOC)
static hwloc_topology_t MR_hw_topology;
static hwloc_cpuset_t MR_hw_available_pus = NULL;
#elif defined(MR_HAVE_LINUX_CPU_AFFINITY_API)
// The number of CPUs that can be represented by MR_cpuset_available.
static int MR_cpuset_num_cpus = 0;
// The size of MR_cpuset_available in bytes, given by
// CPU_ALLOC_SIZE(MR_cpuset_num_cpus).
static size_t MR_cpuset_size = 0;
// A cpuset of MR_cpuset_size bytes, able to represent processors in the
// range [0, MR_cpuset_num_cpus).
// NOTE: the processors available to a process are NOT necessarily
// numbered from 0 to MR_num_processors_detected-1.
static cpu_set_t *MR_cpuset_available;
#endif
#if defined(MR_LL_PARALLEL_CONJ) && defined(MR_HAVE_THREAD_PINNING)
// Variables for thread pinning.
MR_bool MR_thread_pinning = MR_FALSE;
static MercuryLock MR_thread_pinning_lock;
static unsigned MR_num_threads_left_to_pin;
MR_Unsigned MR_primordial_thread_cpu;
#endif
#endif // MR_THREAD_SAFE
#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_ws_engines = 0;
static MR_Integer volatile MR_num_outstanding_contexts = 0;
static MercurySem shutdown_ws_semaphore;
static MercuryLock MR_par_cond_stats_lock;
// This array will contain MR_max_engines pointers to deques.
// The slot i points to the spark deque of engine id i.
// Slots are NULL for unallocated engines.
MR_SparkDeque **MR_spark_deques = NULL;
#endif
////////////////////////////////////////////////////////////////////////////
#ifdef MR_THREAD_SAFE
// Initialize or reset the cpuset that tracks which CPUs are available for
// binding.
static void MR_init_available_cpus_and_detect_num_processors(void);
static void MR_reset_available_cpus(void);
// Free the cpuset if allocated.
static void MR_free_available_cpus(void);
#endif
#ifdef MR_LL_PARALLEL_CONJ
static void MR_setup_num_ws_engines(unsigned num_processors_detected);
// Try to wake up a sleeping engine and tell it to do action. The engine is
// only woken if it is in the sleeping state. If the engine is not sleeping
// use try_notify_engine below. If the engine is woken without a race, 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);
// Send a notification to the engine. This is applicable if the engine is
// in any other state (not sleeping). This function does not use the
// semaphore so it cannot wake a sleeping engine. Don't confuse the
// dropable and non-dropable notifications with the notify/wake methods.
// The only connection is that in general non-dropable notifications should
// be used wit try_notify_engine.
//
// The engine's current state must be passed in engine_state as it is used
// with the CAS operation.
static MR_bool try_notify_engine(MR_EngineId engine_id, int action,
union MR_engine_wake_action_data *action_data,
MR_Unsigned engine_state);
#endif // MR_LL_PARALLEL_CONJ
#ifdef MR_PROFILE_PARALLEL_EXECUTION_SUPPORT
// Write out the profiling data that we collect during execution.
static void MR_write_out_profiling_parallel_execution(void);
#endif
#if defined(MR_LL_PARALLEL_CONJ) && defined(MR_HAVE_THREAD_PINNING)
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);
// 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
MR_sem_init(&shutdown_ws_semaphore, 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
MR_init_available_cpus_and_detect_num_processors();
#ifndef MR_HAVE_THREAD_PINNING
MR_free_available_cpus();
#endif
MR_setup_num_ws_engines(MR_num_processors_detected);
#ifdef MR_HAVE_THREAD_PINNING
MR_setup_thread_pinning();
#endif
MR_granularity_wsdeque_length =
MR_granularity_wsdeque_length_factor * MR_num_ws_engines;
MR_spark_deques = MR_GC_NEW_ARRAY_ATTRIB(MR_SparkDeque*,
MR_max_engines, MR_ALLOC_SITE_RUNTIME);
for (i = 0; i < MR_max_engines; i++) {
MR_spark_deques[i] = NULL;
}
engine_sleep_sync_data = MR_GC_NEW_ARRAY_ATTRIB(engine_sleep_sync,
MR_max_engines, MR_ALLOC_SITE_RUNTIME);
for (i = 0; i < MR_max_engines; i++) {
engine_sleep_sync *esync = get_engine_sleep_sync(i);
MR_sem_init(&esync->d.es_sleep_semaphore, 0);
pthread_mutex_init(&esync->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).
esync->d.es_state = ENGINE_STATE_WORKING;
esync->d.es_action = MR_ENGINE_ACTION_NONE;
}
#endif
#endif // MR_THREAD_SAFE
}
#ifdef MR_THREAD_SAFE
unsigned
MR_get_num_processors(void)
{
unsigned result;
MR_OBTAIN_GLOBAL_LOCK("MR_get_num_processors");
// In low-level threaded grades, MR_num_processors_detected is initialised
// at startup to count the number of work-stealing engines to run.
// In high-level grades, MR_num_processors_detected is initialised on
// demand.
if (MR_num_processors_detected == 0) {
MR_init_available_cpus_and_detect_num_processors();
MR_free_available_cpus();
}
result = MR_num_processors_detected;
MR_RELEASE_GLOBAL_LOCK("MR_get_num_processors");
return result;
}
static void
MR_init_available_cpus_and_detect_num_processors(void)
{
#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
MR_reset_available_cpus();
#if defined(MR_HAVE_HWLOC)
MR_num_processors_detected = hwloc_bitmap_weight(MR_hw_available_pus);
#elif defined(MR_HAVE_LINUX_CPU_AFFINITY_API)
MR_num_processors_detected =
CPU_COUNT_S(MR_cpuset_size, MR_cpuset_available);
#elif defined(MR_WIN32_GETSYSTEMINFO)
{
SYSTEM_INFO sysinfo;
GetSystemInfo(&sysinfo);
MR_num_processors_detected = sysinfo.dwNumberOfProcessors;
}
#elif defined(MR_HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
{
long n = sysconf(_SC_NPROCESSORS_ONLN);
if (n > 0) {
MR_num_processors_detected = n;
}
}
#endif
}
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_bitmap_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 are 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
// available, it didn't exclude cpus not in the processor's cpuset(7).
if (MR_hw_available_pus == NULL) {
MR_hw_available_pus = hwloc_bitmap_alloc();
}
hwloc_bitmap_and(MR_hw_available_pus, inherited_binding,
hwloc_topology_get_allowed_cpuset(MR_hw_topology));
hwloc_bitmap_free(inherited_binding);
#elif defined(MR_HAVE_LINUX_CPU_AFFINITY_API)
int num_cpus;
size_t cpuset_size = 0;
cpu_set_t *cpuset = NULL;
if (MR_cpuset_num_cpus > 0) {
// Start with the same cpuset size that we determined in a previous
// call to this function.
num_cpus = MR_cpuset_num_cpus;
} else {
// The minimum cpuset size on 32-bit architectures is 32-bits.
num_cpus = 32;
#if defined(MR_HAVE_SYSCONF) && defined(_SC_NPROCESSORS_ONLN)
{
long n = sysconf(_SC_NPROCESSORS_ONLN);
if (n > 0) {
num_cpus = n;
}
}
#endif
}
// Free an existing cpuset if we have been here before.
if (MR_cpuset_available != NULL) {
CPU_FREE(MR_cpuset_available);
MR_cpuset_available = NULL;
MR_cpuset_size = 0;
MR_cpuset_num_cpus = 0;
}
// This huge limit is just to prevent the possibility of looping forever.
// In most cases we will succeed on the first attempt.
while (num_cpus <= 0x100000) {
int err;
cpuset_size = CPU_ALLOC_SIZE(num_cpus);
cpuset = CPU_ALLOC(num_cpus);
if (cpuset == NULL) {
break;
}
if (sched_getaffinity(0, cpuset_size, cpuset) == 0) {
break;
}
err = errno;
CPU_FREE(cpuset);
cpuset = NULL;
if (err != EINVAL) {
break;
}
// sched_getaffinity() can return EINVAL if the kernel uses larger
// CPU affinity masks than we provided for. Then we must retry with
// a larger cpuset buffer.
if (num_cpus < 512) {
num_cpus = 512;
} else {
num_cpus *= 2;
}
}
if (cpuset != NULL) {
MR_cpuset_num_cpus = num_cpus;
MR_cpuset_size = cpuset_size;
MR_cpuset_available = cpuset;
} else {
MR_perror("Couldn't get CPU affinity");
#if defined(MR_LL_PARALLEL_CONJ) && defined(MR_HAVE_THREAD_PINNING)
MR_thread_pinning = MR_FALSE;
#endif
}
#endif
}
static void
MR_free_available_cpus(void)
{
#if defined(MR_HAVE_HWLOC)
// XXX Fill this in.
#elif defined(MR_HAVE_LINUX_CPU_AFFINITY_API)
MR_cpuset_size = 0;
if (MR_cpuset_available != NULL) {
CPU_FREE(MR_cpuset_available);
MR_cpuset_available = NULL;
}
#endif
}
#endif // MR_THREAD_SAFE
#ifdef MR_LL_PARALLEL_CONJ
static void
MR_setup_num_ws_engines(unsigned num_processors_detected)
{
// If MR_num_ws_engines is unset, configure it to match the number of
// processors available to the process (if known). If we do this, then we
// prepare to set processor affinities later on.
if (MR_num_ws_engines == 0) {
MR_num_ws_engines = num_processors_detected;
// In case CPU detection failed for some reason.
if (MR_num_ws_engines == 0) {
MR_num_ws_engines = 1;
}
}
if (MR_debug_threads) {
fprintf(stderr, "Detected %d processors, will use %d ws engines\n",
num_processors_detected, MR_num_ws_engines);
}
}
#endif // MR_LL_PARALLEL_CONJ
// Thread pinning.
#if defined(MR_HAVE_THREAD_PINNING) && defined(MR_LL_PARALLEL_CONJ)
static int
MR_pin_thread_no_locking(void)
{
int initial_cpu;
int max;
int i;
initial_cpu = MR_current_cpu();
#ifdef MR_DEBUG_THREAD_PINNING
fprintf(stderr, "Currently running on cpu %d\n", initial_cpu);
#endif
#if defined(MR_HAVE_HWLOC)
max = MR_num_processors_detected;
#elif defined(MR_HAVE_LINUX_CPU_AFFINITY_API)
// CPUs available to this process do not have to be numbered consecutively.
max = MR_cpuset_num_cpus;
#else
#error Should be unreachable
#endif
for (i = 0; (i < max) && MR_thread_pinning; i++) {
int target_cpu = (initial_cpu + i) % max;
if (MR_do_pin_thread(target_cpu)) {
#ifdef MR_DEBUG_THREAD_PINNING
fprintf(stderr, "Pinned to cpu %d, running on cpu %d\n",
target_cpu, MR_current_cpu());
#endif
MR_num_threads_left_to_pin--;
MR_make_cpu_unavailable(target_cpu);
return target_cpu;
}
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 CPU has already had a thread pinned to it.
fprintf(stderr, "Couldn't pin Mercury engine to processor");
break;
}
}
return initial_cpu;
}
int
MR_pin_thread(void)
{
int 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;
}
int
MR_pin_primordial_thread(void)
{
// We don't need locking to pin the primordial thread as it is called
// before any other threads exist.
return MR_pin_thread_no_locking();
}
static void MR_setup_thread_pinning(void)
{
MR_num_threads_left_to_pin = MR_num_ws_engines;
pthread_mutex_init(&MR_thread_pinning_lock, MR_MUTEX_ATTR);
// Restore this to enable thread pinning by default
// if we autodetected the number of CPUs without error.
#if 0
if (MR_num_processors_detected > 1) {
MR_thread_pinning = MR_TRUE;
}
#endif
}
// Determine which CPU this thread is currently running on.
static int MR_current_cpu(void)
{
int os_cpu;
#if defined(MR_HAVE_HWLOC)
hwloc_obj_t pu;
pu = hwloc_get_pu_obj_by_os_index(MR_hw_topology, os_cpu);
if (pu != NULL) {
os_cpu = pu->logical_index;
} else {
// XXX Quick hack to prevent crashes only.
os_cpu = -1;
}
#elif defined(MR_HAVE_SCHED_GETCPU)
os_cpu = sched_getcpu();
#else
os_cpu = 0;
#endif
if (os_cpu < 0) {
os_cpu = 0;
if (MR_thread_pinning) {
MR_perror("Warning: unable to determine the current CPU for "
"this thread: ");
}
}
return os_cpu;
}
static MR_bool
MR_do_pin_thread(int cpu)
{
// Make sure that we are allowed to bind to this CPU.
#if defined(MR_HAVE_HWLOC)
hwloc_obj_t pu;
if (hwloc_bitmap_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_bitmap_intersects(MR_hw_available_pus, pu->cpuset)) {
return MR_FALSE;
}
#elif defined(MR_HAVE_LINUX_CPU_AFFINITY_API)
if (CPU_COUNT_S(MR_cpuset_size, MR_cpuset_available) == 0) {
// As above, reset the available cpus.
MR_reset_available_cpus();
}
if (!CPU_ISSET_S(cpu, MR_cpuset_size, MR_cpuset_available)) {
return MR_FALSE;
}
#endif
#if defined(MR_HAVE_HWLOC)
errno = hwloc_set_cpubind(MR_hw_topology, pu->cpuset,
HWLOC_CPUBIND_THREAD);
if (errno != 0) {
MR_perror("Warning: Couldn't set CPU affinity: ");
MR_thread_pinning = MR_FALSE;
return MR_FALSE;
}
#elif defined(MR_HAVE_LINUX_CPU_AFFINITY_API)
size_t cpuset_size;
cpu_set_t *cpuset;
MR_bool success;
// The man page for sched_setaffinity() says that Linux 2.6.9 and earlier
// may return EINVAL if given a cpuset size smaller than size of the
// affinity mask used by the kernel, so we allocate a cpuset large enough
// for MR_cpuset_num_cpus, not just cpu.
cpuset_size = CPU_ALLOC_SIZE(MR_cpuset_num_cpus);
cpuset = CPU_ALLOC(MR_cpuset_num_cpus);
if (cpuset != NULL) {
CPU_ZERO_S(cpuset_size, cpuset);
CPU_SET_S(cpu, cpuset_size, cpuset);
if (sched_setaffinity(0, cpuset_size, cpuset) == 0) {
success = MR_TRUE;
} else {
MR_perror("Warning: Couldn't set CPU affinity: ");
// If this failed once, it will probably fail again.
// Disable thread pinning from now on.
MR_thread_pinning = MR_FALSE;
success = MR_FALSE;
}
CPU_FREE(cpuset);
} else {
success = MR_FALSE;
}
return success;
#endif
return MR_TRUE;
}
#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_bitmap_asprintf(&cpusetstr, MR_hw_available_pus);
fprintf(stderr, "Old available CPU set: %s\n", cpusetstr);
free(cpusetstr);
hwloc_bitmap_asprintf(&cpusetstr, pu->cpuset);
fprintf(stderr, "Making this CPU set unavailable: %s\n", cpusetstr);
free(cpusetstr);
#endif
hwloc_bitmap_andnot(MR_hw_available_pus, MR_hw_available_pus, pu->cpuset);
#ifdef MR_DEBUG_THREAD_PINNING
hwloc_bitmap_asprintf(&cpusetstr, MR_hw_available_pus);
fprintf(stderr, "New available CPU set: %s\n", cpusetstr);
free(cpusetstr);
#endif
siblings_to_make_unavailable = hwloc_bitmap_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 have 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_bitmap_intersects(core->children[i]->cpuset,
MR_hw_available_pus)) {
if (!MR_make_pu_unavailable(core->children[i])) {
return MR_FALSE;
}
}
}
}
return MR_TRUE;
}
#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_LINUX_CPU_AFFINITY_API)
CPU_CLR_S(cpu, MR_cpuset_size, MR_cpuset_available);
#endif
}
void MR_done_thread_pinning(void)
{
MR_free_available_cpus();
}
#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
MR_sem_destroy(&shutdown_ws_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:
MR_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)
{
#ifndef MR_HIGHLEVEL_CODE
const char *detstack_name;
const char *nondetstack_name;
size_t detstack_size;
size_t nondetstack_size;
#endif
c->MR_ctxt_id = id;
c->MR_ctxt_next = NULL;
c->MR_ctxt_resume = NULL;
#ifdef MR_THREAD_SAFE
c->MR_ctxt_exclusive_engine = MR_ENGINE_ID_NONE;
c->MR_ctxt_resume_engine = 0;
c->MR_ctxt_resume_engine_required = MR_FALSE;
c->MR_ctxt_resume_c_depth = 0;
c->MR_ctxt_resume_stack = 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_resume_stack == 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_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)
c->MR_ctxt_thread_local_mutables = NULL;
#ifdef MR_LL_PARALLEL_CONJ
MR_atomic_dec_int(&MR_num_outstanding_contexts);
#endif
MR_LOCK(&free_context_list_lock, "release_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, "release_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: %" MR_INTEGER_LENGTH_MODIFIER
"u, 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 %p requires engine %d and c_depth %"
MR_INTEGER_LENGTH_MODIFIER "u\n",
MR_SELF_THREAD_ID, cur, cur->MR_ctxt_resume_engine,
cur->MR_ctxt_resume_c_depth);
}
#endif
if ((cur->MR_ctxt_resume_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 if (cur->MR_ctxt_exclusive_engine != MR_ENGINE_ID_NONE) {
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Context %p requires exclusive engine %d\n",
MR_SELF_THREAD_ID, cur, cur->MR_ctxt_exclusive_engine);
}
#endif
if (cur->MR_ctxt_exclusive_engine == engine_id) {
// This context is exclusive to this engine.
preferred_context = cur;
preferred_context_prev = prev;
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_engine);
}
#endif
if (cur->MR_ctxt_resume_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;
int victim_id;
int max_victim_id;
MR_SparkDeque *victim;
int steal_result;
MR_bool result = MR_FALSE;
offset = MR_ENGINE(MR_eng_victim_counter);
// This is the highest victim to attempt stealing from. We do not
// steal from exclusive engines, numbered from MR_num_ws_engines up.
// To try that out, set max_victim_id to MR_highest_engine_id and
// change the condition in MR_fork_new_child.
max_victim_id = MR_num_ws_engines;
for (i = 0; i < max_victim_id; i++) {
victim_id = (i + offset) % max_victim_id;
if (victim_id == MR_ENGINE(MR_eng_id)) {
// There is no point in stealing from ourselves.
continue;
}
// The victim engine may be shutting down as we attempt to steal from
// it. However, the spark deque is allocated separately so that it may
// outlive the engine, and since the spark deque must be empty when the
// engine is destroyed, any attempt to steal from it must fail.
victim = MR_spark_deques[victim_id];
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) = victim_id;
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
}
#ifndef MR_HIGHLEVEL_CODE
// 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.
static int
MR_check_pending_contexts(MR_bool block)
{
#ifdef MR_CAN_DO_PENDING_IO
int err;
char errbuf[MR_STRERROR_BUF_SIZE];
int max_fd;
int num_fds;
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;
}
// The following code (and the select interface in general) assumes that
// relevant file descriptors are all < FD_SETSIZE, but some systems allow
// the file descriptor limit to be raised higher.
// Fixing this potential problem is not a high priority as pending I/O is
// not actually implemented.
MR_fd_zero(&rd_set0);
MR_fd_zero(&wr_set0);
MR_fd_zero(&ex_set0);
max_fd = -1;
for (pctxt = MR_pending_contexts ; pctxt ; pctxt = pctxt -> next) {
if (pctxt->waiting_mode & MR_PENDING_READ) {
if (max_fd > pctxt->fd) {
max_fd = pctxt->fd;
}
FD_SET(pctxt->fd, &rd_set0);
}
if (pctxt->waiting_mode & MR_PENDING_WRITE) {
if (max_fd > pctxt->fd) {
max_fd = pctxt->fd;
}
FD_SET(pctxt->fd, &wr_set0);
}
if (pctxt->waiting_mode & MR_PENDING_EXEC) {
if (max_fd > pctxt->fd) {
max_fd = pctxt->fd;
}
FD_SET(pctxt->fd, &ex_set0);
}
}
// If max_fd is still -1, then we have no file descriptors.
// If max_fd is not -1, then we *do* some file descriptors.
// Their numbers can range from 0 to max_fd, which encompasses
// max_fd+1 possible file descriptors.
num_fds = max_fd + 1;
if (num_fds == 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(num_fds, &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(num_fds, &rd_set, &wr_set, &ex_set, &timeout);
} while (err == -1 && MR_is_eintr(errno));
}
if (err < 0) {
MR_fatal_error("select failed: %s",
MR_strerror(errno, errbuf, sizeof(errbuf)));
}
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 // !MR_CAN_DO_PENDING_IO
}
#endif // not MR_HIGHLEVEL_CODE
void
MR_schedule_context(MR_Context *ctxt)
{
#ifdef MR_LL_PARALLEL_CONJ
MR_EngineId engine_id;
MR_bool engine_required;
union MR_engine_wake_action_data notify_context_data;
engine_sleep_sync *esync;
notify_context_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.
if (ctxt->MR_ctxt_resume_engine_required == MR_TRUE) {
engine_id = ctxt->MR_ctxt_resume_engine;
engine_required = MR_TRUE;
} else if (ctxt->MR_ctxt_exclusive_engine != MR_ENGINE_ID_NONE) {
engine_id = ctxt->MR_ctxt_exclusive_engine;
engine_required = MR_TRUE;
} else {
engine_id = ctxt->MR_ctxt_resume_engine;
engine_required = MR_FALSE;
}
esync = get_engine_sleep_sync(engine_id);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Scheduling context %p desired engine: %d required: %d\n",
MR_SELF_THREAD_ID, ctxt, engine_id, engine_required);
}
#endif
if (engine_required) {
// 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 engine %d\n",
MR_SELF_THREAD_ID, engine_id);
}
#endif
// Only engine_id may execute this context, if it is sleeping
// attempt to wake it.
if (esync->d.es_state == ENGINE_STATE_SLEEPING) {
if (try_wake_engine(engine_id, MR_ENGINE_ACTION_CONTEXT,
&notify_context_data))
{
// 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_ws_engines > 0) {
if (MR_try_wake_ws_engine(engine_id, MR_ENGINE_ACTION_CONTEXT,
&notify_context_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
if (engine_required) {
// The engine is only runnable on a single context, that context was
// busy earlier and couldn't be handed the engine. If that context
// is now idle or stealing it may have already checked the runqueue
// (where we just put the context). Therefore we re-attempt to
// notify the engine to ensure that it re-checks the runqueue.
//
// This is only a problem when only a single engine can execute a
// context. In any other case the current engine will eventually check
// the runqueue.
//
// The updates to the run queue are guaranteed by the compiler and
// the processor to be visible before the runqueue is unlocked.
// And the engine's update of its state from working->idle will be
// available before it can lock the runqueue. Therefore, if the
// engine is working we do not message it because it will check the
// runqueue anyway.
MR_Unsigned state;
state = esync->d.es_state;
while (state & (ENGINE_STATE_SLEEPING | ENGINE_STATE_IDLE |
ENGINE_STATE_STEALING)) {
if (state == ENGINE_STATE_SLEEPING) {
if (try_wake_engine(engine_id,
MR_ENGINE_ACTION_CONTEXT_ADVICE, NULL)) {
break;
}
} else if ((state == ENGINE_STATE_IDLE)
|| (state == ENGINE_STATE_STEALING)) {
if (try_notify_engine(engine_id,
MR_ENGINE_ACTION_CONTEXT_ADVICE, NULL, state)) {
break;
}
}
MR_sched_yield();
state = esync->d.es_state;
}
}
#endif // MR_LL_PARALLEL_CONJ
}
#ifdef MR_LL_PARALLEL_CONJ
void
MR_verify_initial_engine_sleep_sync(MR_EngineId id)
{
engine_sleep_sync *esync = get_engine_sleep_sync(id);
assert(esync->d.es_state == ENGINE_STATE_WORKING);
assert(esync->d.es_action == MR_ENGINE_ACTION_NONE);
}
void
MR_verify_final_engine_sleep_sync(MR_EngineId id, MR_EngineType engine_type)
{
engine_sleep_sync *esync = get_engine_sleep_sync(id);
// Shared engines are shut down by notification.
// Exclusive engines are shut down at the end of the Mercury thread.
if (engine_type == MR_ENGINE_TYPE_SHARED) {
assert(esync->d.es_state == ENGINE_STATE_NOTIFIED);
} else {
assert(esync->d.es_state == ENGINE_STATE_WORKING);
}
assert(esync->d.es_action == MR_ENGINE_ACTION_NONE);
}
// Try to wake a work-stealing engine, starting at the preferred engine.
MR_bool
MR_try_wake_ws_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;
MR_Unsigned valid_states;
// Set the valid set of states that can be notified for this action.
switch (action) {
case MR_ENGINE_ACTION_SHUTDOWN:
case MR_ENGINE_ACTION_CONTEXT_ADVICE:
valid_states = ENGINE_STATE_IDLE | ENGINE_STATE_STEALING |
ENGINE_STATE_SLEEPING;
break;
case MR_ENGINE_ACTION_WORKSTEAL_ADVICE:
valid_states = ENGINE_STATE_STEALING | ENGINE_STATE_SLEEPING;
break;
case MR_ENGINE_ACTION_CONTEXT:
valid_states = ENGINE_STATE_SLEEPING;
break;
default:
abort();
}
// 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_ws_engines; i++) {
current_engine = (i + preferred_engine) % MR_num_ws_engines;
if (current_engine == MR_ENGINE(MR_eng_id)) {
// Don't post superfluous events to ourself.
continue;
}
state = get_engine_sleep_sync(current_engine)->d.es_state;
if (state & valid_states) {
switch (state) {
case ENGINE_STATE_SLEEPING:
result = try_wake_engine(current_engine,
action, action_data);
if (result) {
goto success;
}
break;
case ENGINE_STATE_IDLE:
case ENGINE_STATE_STEALING:
result = try_notify_engine(current_engine, action,
action_data, state);
if (result) {
goto success;
}
break;
}
}
}
return MR_FALSE;
success:
if (target_eng) {
*target_eng = current_engine;
}
return MR_TRUE;
}
static MR_bool
try_wake_engine(MR_EngineId engine_id, int action,
union MR_engine_wake_action_data *action_data)
{
MR_bool success = MR_FALSE;
engine_sleep_sync *esync = get_engine_sleep_sync(engine_id);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Trying to wake up engine %d, action %d\n",
MR_SELF_THREAD_ID, engine_id, action);
}
#endif
// Our caller made an initial check of the engine's state. But we check
// it again after taking the lock.
MR_LOCK(&(esync->d.es_wake_lock), "try_wake_engine, wake_lock");
if (esync->d.es_state == ENGINE_STATE_SLEEPING) {
if (engine_id < MR_num_ws_engines) {
MR_atomic_dec_int(&MR_num_idle_ws_engines);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Decrement MR_num_idle_ws_engines %"
MR_INTEGER_LENGTH_MODIFIER "d\n",
MR_SELF_THREAD_ID, MR_num_idle_ws_engines);
}
#endif
}
// 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_NOTIFIED;
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");
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Wake result %d\n",
MR_SELF_THREAD_ID, success);
}
#endif
return success;
}
MR_bool
try_notify_engine(MR_EngineId engine_id, int action,
union MR_engine_wake_action_data *action_data, MR_Unsigned engine_state)
{
engine_sleep_sync *esync = get_engine_sleep_sync(engine_id);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Trying to notify engine %d, action %d, state %d\n",
MR_SELF_THREAD_ID, engine_id, action, engine_state);
}
#endif
// As in try_wake_engine, we expect our caller to read the current state
// of the engine. But in this case it should also provide the state of
// the engine so we can use it for the CAS below.
if (MR_compare_and_swap_uint(&(esync->d.es_state), engine_state,
ENGINE_STATE_BUSY)) {
// Tell the engine what to do.
esync->d.es_action = action;
if (action_data) {
esync->d.es_action_data = *action_data;
}
if (engine_state == ENGINE_STATE_STEALING) {
// The engine was idle if it was in the stealing state.
// It is not idle anymore so fixup the count.
MR_assert(engine_id < MR_num_ws_engines);
MR_atomic_dec_int(&MR_num_idle_ws_engines);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Decrement MR_num_idle_ws_engines %"
MR_INTEGER_LENGTH_MODIFIER "d\n",
MR_SELF_THREAD_ID, MR_num_idle_ws_engines);
}
#endif
}
// Write the data before we move into the working state.
MR_CPU_SFENCE;
esync->d.es_state = ENGINE_STATE_NOTIFIED;
// We don't adjust the idle engine counter, the engine itself does
// that, especially if this message is dropable.
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Notified engine\n", MR_SELF_THREAD_ID);
}
#endif
return MR_TRUE;
} else {
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Could not notify engine (lost CAS race)\n",
MR_SELF_THREAD_ID);
}
#endif
return MR_FALSE;
}
}
void
MR_shutdown_ws_engines(void)
{
int i;
MR_bool result;
for (i = 0; i < MR_num_ws_engines; i++) {
if (i == MR_ENGINE(MR_eng_id)) {
continue;
}
while (1) {
engine_sleep_sync *esync = get_engine_sleep_sync(i);
MR_Unsigned state = esync->d.es_state;
// We can only notify the engine if it is in the idle or
// sleeping states. Only in these states can we be sure that
// the engine will observe our message. If it is sleeping then
// the semaphore is used for synchronization. If it is idle, it
// must do a CAS before it sleeps (and it cannot work because
// there will be no available work if the system is shutting down.
if (state == ENGINE_STATE_IDLE) {
if (try_notify_engine(i, MR_ENGINE_ACTION_SHUTDOWN, NULL,
state)) {
break;
}
} else if (state == ENGINE_STATE_SLEEPING) {
result = try_wake_engine(i, MR_ENGINE_ACTION_SHUTDOWN,
NULL);
break;
}
// An engine may still appear to be working if this processor
// has not yet seen the other processor write to its state
// field yet. If this happens, wait until it does.
//
// Yield to the OS because we cannot know how long we may have
// to wait.
MR_sched_yield();
}
}
for (i = 0; i < (MR_num_ws_engines - 1); i++) {
int err;
do {
err = MR_SEM_WAIT(&shutdown_ws_semaphore, "MR_shutdown_ws_engines");
} while (err == -1 && MR_SEM_IS_EINTR(errno));
}
}
#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.
//
#ifdef MR_THREAD_SAFE
static void
action_shutdown_ws_engine(void);
static MR_Code*
action_worksteal(MR_EngineId victim_engine_id);
// This always returns a valid code address.
static MR_Code*
action_context(MR_Context *context);
#endif // MR_THREAD_SAFE
// 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_worksteal);
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);
#endif // MR_THREAD_SAFE
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;
MR_EngineId engine_id = MR_ENGINE(MR_eng_id);
engine_sleep_sync *esync = get_engine_sleep_sync(engine_id);
// We can set the idle status without a compare and swap. There are no
// notifications that could have arrived while the engine was working,
// and that cannot safely be ignored. This is a deliberate design
// choice, to avoid a compare and swap in the common state transitions
// between idle and working, and vice versa.
//
// We must advertise that we are in the idle state now (even if we are
// about to find work) before checking the context run queue.
// schedule_context() requires this so that it can reliably deliver a
// context advice message.
esync->d.es_state = ENGINE_STATE_IDLE;
// Try to get a context.
jump_target = do_get_context();
if (jump_target != NULL) {
esync->d.es_state = ENGINE_STATE_WORKING;
MR_GOTO(jump_target);
}
jump_target = do_local_spark(NULL);
if (jump_target != NULL) {
esync->d.es_state = ENGINE_STATE_WORKING;
MR_GOTO(jump_target);
}
// TODO: Use multiple entry points into a single MODULE structure.
if (MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED) {
MR_GOTO(MR_ENTRY(MR_do_idle_worksteal));
} else {
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_worksteal)
MR_init_entry_an(MR_do_idle_worksteal);
MR_BEGIN_CODE
MR_define_entry(MR_do_idle_worksteal);
{
MR_Code *jump_target;
MR_EngineId engine_id = MR_ENGINE(MR_eng_id);
engine_sleep_sync *esync = get_engine_sleep_sync(engine_id);
unsigned action;
// Only work-stealing engines beyond this point.
MR_assert(MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED);
if (!MR_compare_and_swap_uint(&(esync->d.es_state), ENGINE_STATE_IDLE,
ENGINE_STATE_STEALING)) {
while (esync->d.es_state == ENGINE_STATE_BUSY) {
MR_ATOMIC_PAUSE;
}
// The compare and swap failed, which means there is a notification.
action = esync->d.es_action;
esync->d.es_action = MR_ENGINE_ACTION_NONE;
switch (action) {
case MR_ENGINE_ACTION_SHUTDOWN:
action_shutdown_ws_engine();
case MR_ENGINE_ACTION_CONTEXT_ADVICE:
MR_GOTO(MR_ENTRY(MR_do_idle));
case MR_ENGINE_ACTION_WORKSTEAL_ADVICE:
jump_target = action_worksteal(
esync->d.es_action_data.MR_ewa_worksteal_engine);
if (jump_target != NULL) {
MR_GOTO(jump_target);
} else {
MR_GOTO(MR_ENTRY(MR_do_idle));
}
case MR_ENGINE_ACTION_CONTEXT:
case MR_ENGINE_ACTION_NONE:
default:
abort();
break;
}
// We attempted to act on the notification but we lost a race above
// when attempting to worksteal. Now we continue into the
// workstealing state.
esync->d.es_state = ENGINE_STATE_STEALING;
}
// The compare and swap must be visible before the increment.
MR_CPU_SFENCE;
MR_atomic_inc_int(&MR_num_idle_ws_engines);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Increment MR_num_idle_ws_engines %d\n",
MR_SELF_THREAD_ID, MR_num_idle_ws_engines);
}
#endif
jump_target = do_work_steal();
if (jump_target != NULL) {
MR_atomic_dec_int(&MR_num_idle_ws_engines);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Decrement MR_num_idle_ws_engines %d\n",
MR_SELF_THREAD_ID, MR_num_idle_ws_engines);
}
#endif
MR_CPU_SFENCE;
esync->d.es_state = 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
// 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);
engine_sleep_sync *esync = get_engine_sleep_sync(engine_id);
MR_Unsigned in_state;
unsigned action;
int result;
MR_Code *jump_target;
MR_Unsigned state;
#ifdef MR_WORKSTEAL_POLLING
struct timespec ts;
struct timeval tv;
#endif
// Shared engines and exclusive engines enter via different states.
if (MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED) {
in_state = ENGINE_STATE_STEALING;
} else {
in_state = ENGINE_STATE_IDLE;
}
if (MR_compare_and_swap_uint(&(esync->d.es_state), in_state,
ENGINE_STATE_SLEEPING)) {
// We have permission to sleep, and must commit to sleeping.
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d going to sleep\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_id));
}
#endif
#ifdef MR_THREADSCOPE
MR_threadscope_post_engine_sleeping();
#endif
retry_sleep:
#if defined(MR_HAVE_GETTIMEOFDAY) && defined(MR_HAVE_SEMAPHORE_H)
#ifdef MR_WORKSTEAL_POLLING
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 = MR_SEM_TIMED_WAIT(&(esync->d.es_sleep_semaphore), &ts,
"MR_do_sleep");
#else
result = MR_SEM_WAIT(&(esync->d.es_sleep_semaphore), "MR_do_sleep");
#endif
if (result != 0) {
// Sem_wait reported an error.
switch (errno) {
case EINTR:
// An interrupt woke the engine, go back to sleep.
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d sleep interrupted\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_id));
}
#endif
goto retry_sleep;
case ETIMEDOUT:
// A wait timed out, check for any sparks.
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d sleep timed out\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_id));
}
#endif
MR_LOCK(&(esync->d.es_wake_lock), "do_sleep, wake_lock");
state = esync->d.es_state;
if (state == ENGINE_STATE_NOTIFIED) {
// A notification occurred after the timeout but
// before we took the lock above.
//
// So set a null jump target and do not get a spark.
// Then we will execute the goto below and wait on
// the semaphore once more, which will instantly
// succeed and proceed to interpret the notification
// below.
jump_target = NULL;
} else {
if (MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED) {
jump_target = do_work_steal();
} else {
jump_target = NULL;
}
if (jump_target != NULL) {
MR_atomic_dec_int(&MR_num_idle_ws_engines);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Decrement MR_num_idle_ws_engines %d\n",
MR_SELF_THREAD_ID, MR_num_idle_ws_engines);
}
#endif
MR_CPU_SFENCE;
esync->d.es_state = ENGINE_STATE_WORKING;
}
}
MR_UNLOCK(&(esync->d.es_wake_lock), "do_sleep, wake_lock");
if (jump_target != NULL) {
MR_GOTO(jump_target);
}
goto retry_sleep;
default:
MR_perror("sem_timedwait");
abort();
}
} // if sem_wait raised an error
#else
MR_fatal_error(
"low-level parallel grades need gettimeofday() and "
"sem_timedwait()\n");
#endif
} else {
// The compare and swap failed, retrieve the new state.
// Wait until the engine state is no-longer busy, indicating that
// the action information is available.
do {
state = esync->d.es_state;
MR_ATOMIC_PAUSE;
} while (state == ENGINE_STATE_BUSY);
// Read state above before reading action below.
MR_CPU_LFENCE;
}
// Either we slept and were notified, or were notified before we slept.
// Either way, check why we were notified.
MR_assert(state == ENGINE_STATE_NOTIFIED);
action = esync->d.es_action;
esync->d.es_action = MR_ENGINE_ACTION_NONE;
switch (action) {
case MR_ENGINE_ACTION_SHUTDOWN:
if (MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED) {
action_shutdown_ws_engine();
} else {
fprintf(stderr, "Mercury runtime: Exclusive engine %d "
"received shutdown action\n", MR_ENGINE(MR_eng_id));
}
break;
case MR_ENGINE_ACTION_WORKSTEAL_ADVICE:
if (MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED) {
jump_target = action_worksteal(
esync->d.es_action_data.MR_ewa_worksteal_engine);
if (jump_target != NULL) {
MR_GOTO(jump_target);
}
}
MR_GOTO(MR_ENTRY(MR_do_idle));
case MR_ENGINE_ACTION_CONTEXT:
MR_GOTO(action_context(esync->d.es_action_data.MR_ewa_context));
case MR_ENGINE_ACTION_CONTEXT_ADVICE:
MR_GOTO(MR_ENTRY(MR_do_idle));
case MR_ENGINE_ACTION_NONE:
default:
fprintf(stderr,
"Mercury runtime: Engine %d woken with no action\n",
MR_ENGINE(MR_eng_id));
break;
} // Switch on action
// Each valid case ends with a GOTO, so execution cannot reach here.
abort();
}
MR_END_MODULE
static void
action_shutdown_ws_engine(void)
{
MR_EngineId engine_id = MR_ENGINE(MR_eng_id);
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d doing ACTION_SHUTDOWN\n",
MR_SELF_THREAD_ID, engine_id);
}
#endif
// The primordial thread has the responsibility of cleaning up
// the Mercury runtime. It cannot exit by this route.
// Exclusive engines also do not exit by this route.
assert(engine_id != 0);
assert(MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED);
MR_finalize_thread_engine();
MR_SEM_POST(&shutdown_ws_semaphore, "MR_do_sleep shutdown_sem");
pthread_exit(0);
}
static MR_Code*
action_worksteal(MR_EngineId victim_engine_id)
{
MR_SparkDeque *victim;
int steal_result;
MR_Spark spark;
engine_sleep_sync *esync;
MR_assert(MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED);
esync = get_engine_sleep_sync(MR_ENGINE(MR_eng_id));
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d workstealing, victim %d\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_id), victim_engine_id);
}
#endif
victim = MR_spark_deques[victim_engine_id];
MR_assert(victim != NULL);
steal_result = MR_wsdeque_steal_top(victim, &spark);
while (steal_result == -1) {
// Collision, relax the CPU and try again.
MR_ATOMIC_PAUSE;
steal_result = MR_wsdeque_steal_top(victim, &spark);
}
if (steal_result == 1) {
esync->d.es_state = ENGINE_STATE_WORKING;
// Steal from this engine next time, it may have more work.
MR_ENGINE(MR_eng_victim_counter) = victim_engine_id;
#ifdef MR_THREADSCOPE
MR_threadscope_post_steal_spark(spark.MR_spark_id);
#endif
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d executing spark\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_id));
}
#endif
prepare_engine_for_spark(&spark);
return spark.MR_spark_resume;
} else {
// The deque is empty, next time try a different deque.
// (+1 will do).
MR_ENGINE(MR_eng_victim_counter) = victim_engine_id + 1;
return NULL;
}
}
static MR_Code*
action_context(MR_Context *context)
{
MR_Code *resume_point;
engine_sleep_sync *esync;
esync = get_engine_sleep_sync(MR_ENGINE(MR_eng_id));
esync->d.es_state = ENGINE_STATE_WORKING;
prepare_engine_for_context(context);
#ifdef MR_DEBUG_STACK_SEGMENTS
MR_debug_log_message("resuming old context: %p",
context);
#endif
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr,
"%ld Engine %d running context %p from action\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_id), context);
}
#endif
resume_point = (MR_Code*)(context->MR_ctxt_resume);
context->MR_ctxt_resume = NULL;
return resume_point;
}
#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
// We can only read the runqueue head after the store to engine's state
// has finished.
MR_CPU_MFENCE;
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
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d resuming context %p\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_id), 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_assert(context->MR_ctxt_exclusive_engine == MR_ENGINE_ID_NONE
|| context->MR_ctxt_exclusive_engine == MR_ENGINE(MR_eng_id));
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 onto 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;
MR_assert(MR_ENGINE(MR_eng_type) == MR_ENGINE_TYPE_SHARED);
#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.
//
// This condition is simply a crude way to limit memory consumption by
// parallel execution. It is currently affected by contexts created for
// explicit concurrency, which may be surprising.
// XXX why the non-strict inequality?
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
#ifdef MR_DEBUG_THREADS
if (MR_debug_threads) {
fprintf(stderr, "%ld Engine %d executing spark\n",
MR_SELF_THREAD_ID, MR_ENGINE(MR_eng_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_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;
}
#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);
MR_Code *jump_target;
#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_yield or spin waiting
MR_ATOMIC_PAUSE;
}
// We must read the resume label before we read the context as
// the context is written first.
MR_CPU_LFENCE;
#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 {
volatile MR_Spark *spark;
#ifdef MR_THREADSCOPE
MR_threadscope_post_looking_for_local_spark();
#endif
spark = MR_wsdeque_pop_bottom(MR_ENGINE(MR_eng_spark_deque));
if (spark != NULL) {
if ((this_context == jnc_st->MR_st_orig_context) &&
(spark->MR_spark_sync_term != jnc_st)) {
// This spark is not compatible with the context.
//
// Change the context.
#ifdef MR_THREADSCOPE
MR_threadscope_post_stop_context(MR_TS_STOP_REASON_BLOCKED);
#endif
save_dirty_context(join_label);
if (MR_runqueue_head != NULL) {
// There might be a suspended context. We should try
// to execute that.
MR_wsdeque_putback_bottom(MR_ENGINE(MR_eng_spark_deque),
(MR_Spark*) spark);
return MR_ENTRY(MR_do_idle);
}
}
prepare_engine_for_spark(spark);
return spark->MR_spark_resume;
} else {
if (this_context == jnc_st->MR_st_orig_context) {
// 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);
} else {
// This engine and context should look for other work.
#ifdef MR_THREADSCOPE
MR_threadscope_post_stop_context(MR_TS_STOP_REASON_FINISHED);
#endif
}
return MR_ENTRY(MR_do_idle);
}
}
}
#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_worksteal();
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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