Various improvements to example task systems in examples/.
- Only have a single copy of all of the tasks_*.cpp sample implementations, stored in examples/. - Reduce dynamic storage allocation and locking in task launch code paths. - Don't have a hard limit of the number of tasks that can be launched on Windows (fix issue #85).
This commit is contained in:
Matt Pharr
294
examples/tasks_pthreads.cpp
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294
examples/tasks_pthreads.cpp
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/*
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Copyright (c) 2011, Intel Corporation
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of Intel Corporation nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
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OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "taskinfo.h"
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#include <pthread.h>
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#include <semaphore.h>
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#include <string.h>
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#include <unistd.h>
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#include <assert.h>
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#include <stdio.h>
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#include <fcntl.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/param.h>
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#include <sys/sysctl.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <errno.h>
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static int initialized = 0;
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static volatile int32_t lock = 0;
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static int nThreads;
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static pthread_t *threads;
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static pthread_mutex_t taskQueueMutex;
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static int nextTaskToRun;
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static sem_t *workerSemaphore;
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static uint32_t numUnfinishedTasks;
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static pthread_mutex_t tasksRunningConditionMutex;
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static pthread_cond_t tasksRunningCondition;
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// ispc expects these functions to have C linkage / not be mangled
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extern "C" {
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void ISPCLaunch(void *f, void *data);
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void ISPCSync();
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}
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static void *lTaskEntry(void *arg);
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/** Figure out how many CPU cores there are in the system
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*/
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static int
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lNumCPUCores() {
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return sysconf(_SC_NPROCESSORS_ONLN);
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}
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static void
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lTasksInit() {
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nThreads = lNumCPUCores();
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threads = (pthread_t *)malloc(nThreads * sizeof(pthread_t));
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int err;
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if ((err = pthread_mutex_init(&taskQueueMutex, NULL)) != 0) {
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fprintf(stderr, "Error creating mutex: %s\n", strerror(err));
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exit(1);
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}
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char name[32];
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sprintf(name, "ispc_task.%d", (int)getpid());
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workerSemaphore = sem_open(name, O_CREAT, S_IRUSR|S_IWUSR, 0);
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if (!workerSemaphore) {
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fprintf(stderr, "Error creating semaphore: %s\n", strerror(err));
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exit(1);
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}
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if ((err = pthread_cond_init(&tasksRunningCondition, NULL)) != 0) {
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fprintf(stderr, "Error creating condition variable: %s\n", strerror(err));
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exit(1);
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}
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if ((err = pthread_mutex_init(&tasksRunningConditionMutex, NULL)) != 0) {
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fprintf(stderr, "Error creating mutex: %s\n", strerror(err));
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exit(1);
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}
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for (int i = 0; i < nThreads; ++i) {
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err = pthread_create(&threads[i], NULL, &lTaskEntry, (void *)(i));
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if (err != 0) {
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fprintf(stderr, "Error creating pthread %d: %s\n", i, strerror(err));
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exit(1);
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}
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}
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}
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void
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ISPCLaunch(void *f, void *d) {
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int err;
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if (!initialized) {
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while (1) {
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if (lAtomicCompareAndSwap32(&lock, 1, 0) == 0) {
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if (!initialized) {
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lTasksInit();
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__asm__ __volatile__("mfence":::"memory");
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initialized = 1;
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}
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lock = 0;
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break;
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}
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}
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}
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//
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// Acquire mutex, add task
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//
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if ((err = pthread_mutex_lock(&taskQueueMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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// Need a mutex here to ensure we get this filled in before a worker
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// grabs it and starts running...
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TaskInfo *ti = lGetTaskInfo();
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ti->func = f;
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ti->data = d;
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if ((err = pthread_mutex_unlock(&taskQueueMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_unlock: %s\n", strerror(err));
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exit(1);
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}
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//
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// Update count of number of tasks left to run
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//
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if ((err = pthread_mutex_lock(&tasksRunningConditionMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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// FIXME: is this redundant with nextTaskInfoCoordinate?
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++numUnfinishedTasks;
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if ((err = pthread_mutex_unlock(&tasksRunningConditionMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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//
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// Post to the worker semaphore to wake up worker threads that are
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// sleeping waiting for tasks to show up
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//
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if ((err = sem_post(workerSemaphore)) != 0) {
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fprintf(stderr, "Error from sem_post: %s\n", strerror(err));
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exit(1);
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}
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}
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static void *
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lTaskEntry(void *arg) {
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int threadIndex = (int)arg;
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int threadCount = nThreads;
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TaskFuncType func;
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while (1) {
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int err;
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if ((err = sem_wait(workerSemaphore)) != 0) {
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fprintf(stderr, "Error from sem_wait: %s\n", strerror(err));
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exit(1);
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}
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//
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// Acquire mutex, get task
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//
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if ((err = pthread_mutex_lock(&taskQueueMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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if (nextTaskToRun == nextTaskInfoCoordinate) {
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//
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// Task queue is empty, go back and wait on the semaphore
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//
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if ((err = pthread_mutex_unlock(&taskQueueMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_unlock: %s\n", strerror(err));
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exit(1);
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}
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continue;
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}
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int runCoord = nextTaskToRun++;
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int index = (runCoord >> LOG_TASK_QUEUE_CHUNK_SIZE);
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int offset = runCoord & (TASK_QUEUE_CHUNK_SIZE-1);
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TaskInfo *myTask = &taskInfo[index][offset];
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if ((err = pthread_mutex_unlock(&taskQueueMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_unlock: %s\n", strerror(err));
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exit(1);
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}
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//
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// Do work for _myTask_
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//
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func = (TaskFuncType)myTask->func;
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func(myTask->data, threadIndex, threadCount);
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//
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// Decrement the number of unfinished tasks counter
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//
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if ((err = pthread_mutex_lock(&tasksRunningConditionMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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// FIXME: can this be a comparison of (nextTaskToRun == nextTaskInfoCoordinate)?
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// (I don't think so--think there is a race...)
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int unfinished = --numUnfinishedTasks;
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if (unfinished == 0) {
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//
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// Signal the "no more tasks are running" condition if all of
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// them are done.
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//
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int err;
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if ((err = pthread_cond_signal(&tasksRunningCondition)) != 0) {
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fprintf(stderr, "Error from pthread_cond_signal: %s\n", strerror(err));
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exit(1);
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}
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}
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if ((err = pthread_mutex_unlock(&tasksRunningConditionMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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}
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pthread_exit(NULL);
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return 0;
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}
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void ISPCSync() {
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int err;
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if ((err = pthread_mutex_lock(&tasksRunningConditionMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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// As long as there are tasks running, wait on the condition variable;
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// doing so causes this thread to go to sleep until someone signals on
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// the tasksRunningCondition condition variable.
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while (numUnfinishedTasks > 0) {
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if ((err = pthread_cond_wait(&tasksRunningCondition,
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&tasksRunningConditionMutex)) != 0) {
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fprintf(stderr, "Error from pthread_cond_wait: %s\n", strerror(err));
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exit(1);
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}
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}
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lResetTaskInfo();
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nextTaskToRun = 0;
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// We acquire ownership of the condition variable mutex when the above
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// pthread_cond_wait returns.
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// FIXME: is there a lurking issue here if numUnfinishedTasks gets back
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// to zero by the time we get to ISPCSync() and thence we're trying to
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// unlock a mutex we don't have a lock on?
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if ((err = pthread_mutex_unlock(&tasksRunningConditionMutex)) != 0) {
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fprintf(stderr, "Error from pthread_mutex_lock: %s\n", strerror(err));
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exit(1);
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}
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}
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