548 lines
12 KiB
C
548 lines
12 KiB
C
/****************************************************************************
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* fs/vfs/fs_eventfd.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdio.h>
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#include <poll.h>
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <debug.h>
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#include <nuttx/mutex.h>
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#include <sys/ioctl.h>
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#include <sys/eventfd.h>
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#include "inode/inode.h"
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/****************************************************************************
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* Private Types
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****************************************************************************/
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typedef struct eventfd_waiter_sem_s
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{
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sem_t sem;
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FAR struct eventfd_waiter_sem_s *next;
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} eventfd_waiter_sem_t;
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/* This structure describes the internal state of the driver */
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struct eventfd_priv_s
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{
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mutex_t lock; /* Enforces device exclusive access */
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FAR eventfd_waiter_sem_t *rdsems; /* List of blocking readers */
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FAR eventfd_waiter_sem_t *wrsems; /* List of blocking writers */
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eventfd_t counter; /* eventfd counter */
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uint8_t crefs; /* References counts on eventfd (max: 255) */
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/* The following is a list if poll structures of threads waiting for
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* driver events.
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*/
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#ifdef CONFIG_EVENT_FD_POLL
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FAR struct pollfd *fds[CONFIG_EVENT_FD_NPOLLWAITERS];
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#endif
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};
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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static int eventfd_do_open(FAR struct file *filep);
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static int eventfd_do_close(FAR struct file *filep);
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static ssize_t eventfd_do_read(FAR struct file *filep, FAR char *buffer,
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size_t len);
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static ssize_t eventfd_do_write(FAR struct file *filep,
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FAR const char *buffer, size_t len);
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#ifdef CONFIG_EVENT_FD_POLL
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static int eventfd_do_poll(FAR struct file *filep, FAR struct pollfd *fds,
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bool setup);
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#endif
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static int eventfd_blocking_io(FAR struct eventfd_priv_s *dev,
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FAR eventfd_waiter_sem_t *sem,
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FAR eventfd_waiter_sem_t **slist);
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static FAR struct eventfd_priv_s *eventfd_allocdev(void);
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static void eventfd_destroy(FAR struct eventfd_priv_s *dev);
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct file_operations g_eventfd_fops =
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{
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eventfd_do_open, /* open */
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eventfd_do_close, /* close */
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eventfd_do_read, /* read */
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eventfd_do_write, /* write */
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NULL, /* seek */
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NULL, /* ioctl */
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NULL, /* mmap */
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NULL, /* truncate */
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#ifdef CONFIG_EVENT_FD_POLL
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eventfd_do_poll /* poll */
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#endif
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};
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static struct inode g_eventfd_inode =
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{
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NULL, /* i_parent */
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NULL, /* i_peer */
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NULL, /* i_child */
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1, /* i_crefs */
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FSNODEFLAG_TYPE_DRIVER, /* i_flags */
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{
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&g_eventfd_fops /* u */
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}
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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static FAR struct eventfd_priv_s *eventfd_allocdev(void)
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{
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FAR struct eventfd_priv_s *dev;
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dev = (FAR struct eventfd_priv_s *)
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kmm_zalloc(sizeof(struct eventfd_priv_s));
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if (dev)
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{
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/* Initialize the private structure */
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nxmutex_init(&dev->lock);
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nxmutex_lock(&dev->lock);
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dev->crefs++;
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}
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return dev;
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}
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static void eventfd_destroy(FAR struct eventfd_priv_s *dev)
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{
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nxmutex_unlock(&dev->lock);
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nxmutex_destroy(&dev->lock);
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kmm_free(dev);
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}
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static int eventfd_do_open(FAR struct file *filep)
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{
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FAR struct eventfd_priv_s *priv = filep->f_priv;
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int ret;
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/* Get exclusive access to the device structures */
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ret = nxmutex_lock(&priv->lock);
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if (ret < 0)
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{
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return ret;
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}
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if (priv->crefs >= 255)
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{
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/* More than 255 opens; uint8_t would overflow to zero */
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ret = -EMFILE;
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}
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else
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{
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/* Save the new open count on success */
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priv->crefs += 1;
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ret = OK;
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}
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nxmutex_unlock(&priv->lock);
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return ret;
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}
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static int eventfd_do_close(FAR struct file *filep)
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{
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FAR struct eventfd_priv_s *priv = filep->f_priv;
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int ret;
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/* Get exclusive access to the device structures */
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ret = nxmutex_lock(&priv->lock);
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if (ret < 0)
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{
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return ret;
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}
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/* Decrement the references to the driver. If the reference count will
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* decrement to 0, then uninitialize the driver.
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*/
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if (priv->crefs > 1)
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{
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/* Just decrement the reference count and release the semaphore */
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priv->crefs -= 1;
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nxmutex_unlock(&priv->lock);
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return OK;
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}
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/* Re-create the path to the driver. */
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finfo("destroy\n");
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eventfd_destroy(priv);
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return OK;
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}
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static int eventfd_blocking_io(FAR struct eventfd_priv_s *dev,
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FAR eventfd_waiter_sem_t *sem,
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FAR eventfd_waiter_sem_t **slist)
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{
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int ret;
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sem->next = *slist;
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*slist = sem;
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nxmutex_unlock(&dev->lock);
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/* Wait for eventfd to notify */
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ret = nxsem_wait(&sem->sem);
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if (ret < 0)
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{
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FAR eventfd_waiter_sem_t *cur_sem;
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/* Interrupted wait, unregister semaphore
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* TODO ensure that lock wait does not fail (ECANCELED)
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*/
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nxmutex_lock(&dev->lock);
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cur_sem = *slist;
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if (cur_sem == sem)
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{
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*slist = sem->next;
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}
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else
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{
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while (cur_sem)
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{
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if (cur_sem->next == sem)
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{
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cur_sem->next = sem->next;
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break;
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}
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}
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}
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nxmutex_unlock(&dev->lock);
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return ret;
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}
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return nxmutex_lock(&dev->lock);
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}
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static ssize_t eventfd_do_read(FAR struct file *filep, FAR char *buffer,
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size_t len)
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{
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FAR struct eventfd_priv_s *dev = filep->f_priv;
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FAR eventfd_waiter_sem_t *cur_sem;
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ssize_t ret;
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if (len < sizeof(eventfd_t) || buffer == NULL)
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{
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return -EINVAL;
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}
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ret = nxmutex_lock(&dev->lock);
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if (ret < 0)
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{
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return ret;
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}
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/* Wait for an incoming event */
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if (dev->counter == 0)
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{
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eventfd_waiter_sem_t sem;
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if (filep->f_oflags & O_NONBLOCK)
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{
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nxmutex_unlock(&dev->lock);
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return -EAGAIN;
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}
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nxsem_init(&sem.sem, 0, 0);
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do
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{
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ret = eventfd_blocking_io(dev, &sem, &dev->rdsems);
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if (ret < 0)
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{
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nxsem_destroy(&sem.sem);
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return ret;
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}
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}
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while (dev->counter == 0);
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nxsem_destroy(&sem.sem);
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}
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/* Device ready for read */
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if ((filep->f_oflags & EFD_SEMAPHORE) != 0)
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{
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*(FAR eventfd_t *)buffer = 1;
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dev->counter -= 1;
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}
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else
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{
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*(FAR eventfd_t *)buffer = dev->counter;
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dev->counter = 0;
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}
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#ifdef CONFIG_EVENT_FD_POLL
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/* Notify all poll/select waiters */
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poll_notify(dev->fds, CONFIG_EVENT_FD_NPOLLWAITERS, POLLOUT);
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#endif
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/* Notify all waiting writers that counter have been decremented */
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cur_sem = dev->wrsems;
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while (cur_sem != NULL)
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{
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nxsem_post(&cur_sem->sem);
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cur_sem = cur_sem->next;
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}
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dev->wrsems = NULL;
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nxmutex_unlock(&dev->lock);
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return sizeof(eventfd_t);
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}
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static ssize_t eventfd_do_write(FAR struct file *filep,
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FAR const char *buffer, size_t len)
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{
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FAR struct eventfd_priv_s *dev = filep->f_priv;
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FAR eventfd_waiter_sem_t *cur_sem;
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eventfd_t new_counter;
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ssize_t ret;
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if (len < sizeof(eventfd_t) || buffer == NULL ||
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(*(FAR eventfd_t *)buffer == (eventfd_t)-1) ||
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(*(FAR eventfd_t *)buffer == (eventfd_t)0))
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{
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return -EINVAL;
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}
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ret = nxmutex_lock(&dev->lock);
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if (ret < 0)
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{
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return ret;
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}
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new_counter = dev->counter + *(FAR eventfd_t *)buffer;
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if (new_counter < dev->counter)
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{
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eventfd_waiter_sem_t sem;
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/* Overflow detected */
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if (filep->f_oflags & O_NONBLOCK)
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{
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nxmutex_unlock(&dev->lock);
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return -EAGAIN;
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}
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nxsem_init(&sem.sem, 0, 0);
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do
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{
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ret = eventfd_blocking_io(dev, &sem, &dev->wrsems);
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if (ret < 0)
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{
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nxsem_destroy(&sem.sem);
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return ret;
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}
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}
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while ((new_counter = dev->counter + *(FAR eventfd_t *)buffer)
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< dev->counter);
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nxsem_destroy(&sem.sem);
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}
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/* Ready to write, update counter */
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dev->counter = new_counter;
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#ifdef CONFIG_EVENT_FD_POLL
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/* Notify all poll/select waiters */
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poll_notify(dev->fds, CONFIG_EVENT_FD_NPOLLWAITERS, POLLIN);
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#endif
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/* Notify all of the waiting readers */
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cur_sem = dev->rdsems;
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while (cur_sem != NULL)
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{
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nxsem_post(&cur_sem->sem);
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cur_sem = cur_sem->next;
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}
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dev->rdsems = NULL;
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nxmutex_unlock(&dev->lock);
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return sizeof(eventfd_t);
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}
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#ifdef CONFIG_EVENT_FD_POLL
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static int eventfd_do_poll(FAR struct file *filep, FAR struct pollfd *fds,
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bool setup)
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{
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FAR struct eventfd_priv_s *dev = filep->f_priv;
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int ret;
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int i;
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pollevent_t eventset;
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ret = nxmutex_lock(&dev->lock);
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if (ret < 0)
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{
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return ret;
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}
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ret = OK;
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if (!setup)
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{
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/* This is a request to tear down the poll. */
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FAR struct pollfd **slot = (FAR struct pollfd **)fds->priv;
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/* Remove all memory of the poll setup */
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*slot = NULL;
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fds->priv = NULL;
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goto out;
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}
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/* This is a request to set up the poll. Find an available
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* slot for the poll structure reference
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*/
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for (i = 0; i < CONFIG_EVENT_FD_NPOLLWAITERS; i++)
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{
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/* Find an available slot */
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if (!dev->fds[i])
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{
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/* Bind the poll structure and this slot */
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dev->fds[i] = fds;
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fds->priv = &dev->fds[i];
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break;
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}
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}
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if (i >= CONFIG_EVENT_FD_NPOLLWAITERS)
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{
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fds->priv = NULL;
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ret = -EBUSY;
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goto out;
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}
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/* Notify the POLLOUT event if the pipe is not full, but only if
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* there is readers.
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*/
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eventset = 0;
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if (dev->counter < (eventfd_t)-1)
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{
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eventset |= POLLOUT;
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}
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/* Notify the POLLIN event if the pipe is not empty */
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if (dev->counter > 0)
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{
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eventset |= POLLIN;
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}
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poll_notify(&fds, 1, eventset);
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out:
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nxmutex_unlock(&dev->lock);
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return ret;
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}
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#endif
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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int eventfd(unsigned int count, int flags)
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{
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FAR struct eventfd_priv_s *new_dev;
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int new_fd;
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int ret;
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if ((flags & ~(EFD_NONBLOCK | EFD_SEMAPHORE | EFD_CLOEXEC)) != 0)
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{
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ret = -EINVAL;
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goto exit_set_errno;
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}
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/* Allocate instance data for this driver */
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new_dev = eventfd_allocdev();
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if (new_dev == NULL)
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{
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/* Failed to allocate new device */
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ret = -ENOMEM;
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goto exit_set_errno;
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}
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new_dev->counter = count;
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new_fd = file_allocate(&g_eventfd_inode, O_RDWR | flags,
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0, new_dev, 0, true);
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if (new_fd < 0)
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{
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ret = new_fd;
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goto exit_with_dev;
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}
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/* Device is ready for use */
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nxmutex_unlock(&new_dev->lock);
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return new_fd;
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exit_with_dev:
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eventfd_destroy(new_dev);
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exit_set_errno:
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set_errno(-ret);
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return ERROR;
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}
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