nuttx/fs/vfs/fs_timerfd.c

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/****************************************************************************
* fs/vfs/fs_timerfd.c
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <stdio.h>
#include <poll.h>
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <debug.h>
#include <nuttx/wdog.h>
#include <nuttx/mutex.h>
#include <sys/ioctl.h>
#include <sys/timerfd.h>
#include "clock/clock.h"
#include "inode/inode.h"
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/****************************************************************************
* Private Types
****************************************************************************/
typedef struct timerfd_waiter_sem_s
{
sem_t sem;
FAR struct timerfd_waiter_sem_s *next;
} timerfd_waiter_sem_t;
/* This structure describes the internal state of the driver */
struct timerfd_priv_s
{
mutex_t lock; /* Enforces device exclusive access */
FAR timerfd_waiter_sem_t *rdsems; /* List of blocking readers */
int clock; /* Clock to use as the timing base */
int delay; /* If non-zero, used to reset repetitive
* timers */
struct wdog_s wdog; /* The watchdog that provides the timing */
timerfd_t counter; /* timerfd counter */
uint8_t crefs; /* References counts on timerfd (max: 255) */
/* The following is a list if poll structures of threads waiting for
* driver events.
*/
#ifdef CONFIG_TIMER_FD_POLL
FAR struct pollfd *fds[CONFIG_TIMER_FD_NPOLLWAITERS];
#endif
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
static int timerfd_open(FAR struct file *filep);
static int timerfd_close(FAR struct file *filep);
static ssize_t timerfd_read(FAR struct file *filep, FAR char *buffer,
size_t len);
#ifdef CONFIG_TIMER_FD_POLL
static int timerfd_poll(FAR struct file *filep, FAR struct pollfd *fds,
bool setup);
#endif
static int timerfd_blocking_io(FAR struct timerfd_priv_s *dev,
FAR timerfd_waiter_sem_t *sem,
FAR timerfd_waiter_sem_t **slist);
static FAR struct timerfd_priv_s *timerfd_allocdev(void);
static void timerfd_destroy(FAR struct timerfd_priv_s *dev);
static void timerfd_timeout(wdparm_t arg);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_timerfd_fops =
{
timerfd_open, /* open */
timerfd_close, /* close */
timerfd_read, /* read */
NULL, /* write */
NULL, /* seek */
NULL, /* ioctl */
NULL, /* truncate */
NULL, /* mmap */
#ifdef CONFIG_TIMER_FD_POLL
timerfd_poll /* poll */
#endif
};
static struct inode g_timerfd_inode =
{
NULL, /* i_parent */
NULL, /* i_peer */
NULL, /* i_child */
1, /* i_crefs */
FSNODEFLAG_TYPE_DRIVER, /* i_flags */
{
&g_timerfd_fops /* u */
}
};
/****************************************************************************
* Private Functions
****************************************************************************/
static FAR struct timerfd_priv_s *timerfd_allocdev(void)
{
FAR struct timerfd_priv_s *dev;
dev = (FAR struct timerfd_priv_s *)
kmm_zalloc(sizeof(struct timerfd_priv_s));
if (dev)
{
/* Initialize the private structure */
nxmutex_init(&dev->lock);
nxmutex_lock(&dev->lock);
}
return dev;
}
static void timerfd_destroy(FAR struct timerfd_priv_s *dev)
{
wd_cancel(&dev->wdog);
nxmutex_unlock(&dev->lock);
nxmutex_destroy(&dev->lock);
kmm_free(dev);
}
static int timerfd_open(FAR struct file *filep)
{
FAR struct timerfd_priv_s *priv = filep->f_priv;
int ret;
/* Get exclusive access to the device structures */
ret = nxmutex_lock(&priv->lock);
if (ret < 0)
{
return ret;
}
if (priv->crefs >= 255)
{
/* More than 255 opens; uint8_t would overflow to zero */
ret = -EMFILE;
}
else
{
/* Save the new open count on success */
priv->crefs += 1;
ret = OK;
}
nxmutex_unlock(&priv->lock);
return ret;
}
static int timerfd_close(FAR struct file *filep)
{
FAR struct timerfd_priv_s *priv = filep->f_priv;
int ret;
/* Get exclusive access to the device structures */
ret = nxmutex_lock(&priv->lock);
if (ret < 0)
{
return ret;
}
/* Decrement the references to the driver. If the reference count will
* decrement to 0, then uninitialize the driver.
*/
if (priv->crefs > 1)
{
/* Just decrement the reference count and release the semaphore */
priv->crefs--;
nxmutex_unlock(&priv->lock);
return OK;
}
/* Re-create the path to the driver. */
finfo("destroy\n");
timerfd_destroy(priv);
return OK;
}
static int timerfd_blocking_io(FAR struct timerfd_priv_s *dev,
FAR timerfd_waiter_sem_t *sem,
FAR timerfd_waiter_sem_t **slist)
{
int ret;
sem->next = *slist;
*slist = sem;
/* Wait for timerfd to notify */
ret = nxsem_wait(&sem->sem);
if (ret < 0)
{
FAR timerfd_waiter_sem_t *cur_sem;
cur_sem = *slist;
if (cur_sem == sem)
{
*slist = sem->next;
}
else
{
while (cur_sem)
{
if (cur_sem->next == sem)
{
cur_sem->next = sem->next;
break;
}
}
}
}
return ret;
}
static ssize_t timerfd_read(FAR struct file *filep, FAR char *buffer,
size_t len)
{
FAR struct timerfd_priv_s *dev = filep->f_priv;
irqstate_t intflags;
ssize_t ret;
if (len < sizeof(timerfd_t) || buffer == NULL)
{
return -EINVAL;
}
/* Ensure that interrupts are disabled and we do not lose counts
* if expiration occurs after read, but before setting counter
* to zero
*/
intflags = enter_critical_section();
/* Wait for an incoming event */
if (dev->counter == 0)
{
timerfd_waiter_sem_t sem;
if (filep->f_oflags & O_NONBLOCK)
{
leave_critical_section(intflags);
return -EAGAIN;
}
nxsem_init(&sem.sem, 0, 0);
do
{
ret = timerfd_blocking_io(dev, &sem, &dev->rdsems);
if (ret < 0)
{
leave_critical_section(intflags);
nxsem_destroy(&sem.sem);
return ret;
}
}
while (dev->counter == 0);
nxsem_destroy(&sem.sem);
}
*(FAR timerfd_t *)buffer = dev->counter;
dev->counter = 0;
leave_critical_section(intflags);
return sizeof(timerfd_t);
}
#ifdef CONFIG_TIMER_FD_POLL
static int timerfd_poll(FAR struct file *filep, FAR struct pollfd *fds,
bool setup)
{
FAR struct timerfd_priv_s *dev = filep->f_priv;
irqstate_t intflags;
int ret = OK;
int i;
intflags = enter_critical_section();
if (!setup)
{
/* This is a request to tear down the poll. */
FAR struct pollfd **slot = (FAR struct pollfd **)fds->priv;
/* Remove all memory of the poll setup */
*slot = NULL;
fds->priv = NULL;
goto out;
}
/* This is a request to set up the poll. Find an available
* slot for the poll structure reference
*/
for (i = 0; i < CONFIG_TIMER_FD_NPOLLWAITERS; i++)
{
/* Find an available slot */
if (!dev->fds[i])
{
/* Bind the poll structure and this slot */
dev->fds[i] = fds;
fds->priv = &dev->fds[i];
break;
}
}
if (i >= CONFIG_TIMER_FD_NPOLLWAITERS)
{
fds->priv = NULL;
ret = -EBUSY;
goto out;
}
/* Notify the POLLIN event if the counter is not zero */
if (dev->counter > 0)
{
#ifdef CONFIG_TIMER_FD_POLL
poll_notify(dev->fds, CONFIG_TIMER_FD_NPOLLWAITERS, POLLIN);
#endif
}
out:
leave_critical_section(intflags);
return ret;
}
#endif
static void timerfd_timeout(wdparm_t arg)
{
FAR struct timerfd_priv_s *dev = (FAR struct timerfd_priv_s *)arg;
FAR timerfd_waiter_sem_t *cur_sem;
irqstate_t intflags;
/* Disable interrupts to ensure that expiration counter is accessed
* atomically
*/
intflags = enter_critical_section();
/* Increment timer expiration counter */
dev->counter++;
/* If this is a repetitive timer, then restart the watchdog */
if (dev->delay > 0)
{
wd_start(&dev->wdog, dev->delay, timerfd_timeout, arg);
}
#ifdef CONFIG_TIMER_FD_POLL
/* Notify all poll/select waiters */
poll_notify(dev->fds, CONFIG_TIMER_FD_NPOLLWAITERS, POLLIN);
#endif
/* Notify all of the waiting readers */
cur_sem = dev->rdsems;
while (cur_sem != NULL)
{
nxsem_post(&cur_sem->sem);
cur_sem = cur_sem->next;
}
dev->rdsems = NULL;
leave_critical_section(intflags);
}
/****************************************************************************
* Public Functions
****************************************************************************/
int timerfd_create(int clockid, int flags)
{
FAR struct timerfd_priv_s *new_dev;
int new_fd;
int ret;
/* Sanity checks. */
if ((clockid != CLOCK_REALTIME &&
clockid != CLOCK_MONOTONIC &&
clockid != CLOCK_BOOTTIME) ||
(flags & ~(TFD_NONBLOCK | TFD_CLOEXEC)) != 0)
{
ret = -EINVAL;
goto errout;
}
/* Allocate instance data for this driver */
new_dev = timerfd_allocdev();
if (new_dev == NULL)
{
/* Failed to allocate new device */
ret = -ENOMEM;
goto errout;
}
/* Initialize the timer instance */
new_dev->clock = clockid;
new_fd = file_allocate(&g_timerfd_inode, O_RDONLY | flags,
0, new_dev, 0, true);
if (new_fd < 0)
{
ret = new_fd;
goto errout_with_dev;
}
/* Device is ready for use */
nxmutex_unlock(&new_dev->lock);
return new_fd;
errout_with_dev:
timerfd_destroy(new_dev);
errout:
set_errno(-ret);
return ERROR;
}
int timerfd_settime(int fd, int flags,
FAR const struct itimerspec *new_value,
FAR struct itimerspec *old_value)
{
FAR struct timerfd_priv_s *dev;
FAR struct file *filep;
irqstate_t intflags;
sclock_t delay;
int ret;
/* Some sanity checks */
if (!new_value)
{
ret = -EFAULT;
goto errout;
}
if ((flags & ~TFD_TIMER_ABSTIME) != 0)
{
ret = -EINVAL;
goto errout;
}
/* Get file pointer by file descriptor */
ret = fs_getfilep(fd, &filep);
if (ret < 0)
{
goto errout;
}
/* Check fd come from us */
if (!filep->f_inode || filep->f_inode->u.i_ops != &g_timerfd_fops)
{
ret = -EINVAL;
goto errout;
}
dev = (FAR struct timerfd_priv_s *)filep->f_priv;
/* Disable interrupts here to ensure that expiration counter is accessed
* atomicaly.
*/
intflags = enter_critical_section();
if (old_value)
{
/* Get the number of ticks before the underlying watchdog expires */
delay = wd_gettime(&dev->wdog);
/* Convert that to a struct timespec and return it */
clock_ticks2time(delay, &old_value->it_value);
clock_ticks2time(dev->delay, &old_value->it_interval);
}
/* Disarm the timer (in case the timer was already armed when
* timerfd_settime() is called).
*/
wd_cancel(&dev->wdog);
/* Clear expiration counter */
dev->counter = 0;
/* If the it_value member of value is zero, the timer will not be
* re-armed
*/
if (new_value->it_value.tv_sec <= 0 && new_value->it_value.tv_nsec <= 0)
{
leave_critical_section(intflags);
return OK;
}
/* Setup up any repetitive timer */
clock_time2ticks(&new_value->it_interval, &delay);
dev->delay = delay;
/* We need to disable timer interrupts through the following section so
* that the system timer is stable.
*/
/* Check if abstime is selected */
if ((flags & TFD_TIMER_ABSTIME) != 0)
{
/* Calculate a delay corresponding to the absolute time in 'value' */
clock_abstime2ticks(dev->clock, &new_value->it_value, &delay);
}
else
{
/* Calculate a delay assuming that 'value' holds the relative time
* to wait. We have internal knowledge that clock_time2ticks always
* returns success.
*/
clock_time2ticks(&new_value->it_value, &delay);
}
/* If the time is in the past or now, then set up the next interval
* instead (assuming a repetitive timer).
*/
if (delay <= 0)
{
delay = dev->delay;
}
/* Then start the watchdog */
ret = wd_start(&dev->wdog, delay, timerfd_timeout, (wdparm_t)dev);
if (ret < 0)
{
leave_critical_section(intflags);
goto errout;
}
leave_critical_section(intflags);
return OK;
errout:
set_errno(-ret);
return ERROR;
}
int timerfd_gettime(int fd, FAR struct itimerspec *curr_value)
{
FAR struct timerfd_priv_s *dev;
FAR struct file *filep;
sclock_t ticks;
int ret;
/* Some sanity checks */
if (!curr_value)
{
ret = -EFAULT;
goto errout;
}
/* Get file pointer by file descriptor */
ret = fs_getfilep(fd, &filep);
if (ret < 0)
{
goto errout;
}
/* Check fd come from us */
if (!filep->f_inode || filep->f_inode->u.i_ops != &g_timerfd_fops)
{
ret = -EINVAL;
goto errout;
}
dev = (FAR struct timerfd_priv_s *)filep->f_priv;
/* Get the number of ticks before the underlying watchdog expires */
ticks = wd_gettime(&dev->wdog);
/* Convert that to a struct timespec and return it */
clock_ticks2time(ticks, &curr_value->it_value);
clock_ticks2time(dev->delay, &curr_value->it_interval);
return OK;
errout:
set_errno(-ret);
return ERROR;
}