516 lines
14 KiB
C
516 lines
14 KiB
C
/****************************************************************************
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* fs/vfs/fs_poll.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 <poll.h>
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#include <time.h>
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#include <assert.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/clock.h>
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#include <nuttx/semaphore.h>
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#include <nuttx/cancelpt.h>
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#include <nuttx/fs/fs.h>
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#include <nuttx/net/net.h>
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#include <arch/irq.h>
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#include "inode/inode.h"
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: poll_setup
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*
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* Description:
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* Setup the poll operation for each descriptor in the list.
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*
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****************************************************************************/
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static inline int poll_setup(FAR struct pollfd *fds, nfds_t nfds,
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FAR sem_t *sem)
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{
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unsigned int i;
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unsigned int j;
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int ret = OK;
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/* Process each descriptor in the list */
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for (i = 0; i < nfds; i++)
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{
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/* Setup the poll descriptor
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*
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* REVISIT: In a multi-threaded environment, one use case might be to
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* share a single, array of struct pollfd in poll() calls on different
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* threads. That use case is not supportable here because the non-
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* standard internal fields get reset here on each call to poll()
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* on each thread.
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*/
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fds[i].arg = sem;
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fds[i].cb = poll_default_cb;
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fds[i].revents = 0;
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fds[i].priv = NULL;
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/* Check for invalid descriptors. "If the value of fd is less than 0,
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* events shall be ignored, and revents shall be set to 0 in that entry
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* on return from poll()."
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*
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* NOTE: There is a potential problem here. If there is only one fd
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* and if it is negative, then poll will hang. From my reading of the
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* spec, that appears to be the correct behavior.
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*/
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if (fds[i].fd >= 0)
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{
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ret = poll_fdsetup(fds[i].fd, &fds[i], true);
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}
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if (ret < 0)
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{
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/* Setup failed for fds[i]. We now need to teardown previously
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* setup fds[0 .. (i - 1)] to release allocated resources and
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* to prevent memory corruption by access to freed/released 'fds'
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* and 'sem'.
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*/
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for (j = 0; j < i; j++)
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{
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poll_fdsetup(fds[j].fd, &fds[j], false);
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}
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/* Indicate an error on the file descriptor */
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fds[i].revents |= POLLERR;
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return ret;
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}
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}
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return OK;
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}
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/****************************************************************************
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* Name: poll_teardown
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*
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* Description:
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* Teardown the poll operation for each descriptor in the list and return
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* the count of non-zero poll events.
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*
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****************************************************************************/
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static inline int poll_teardown(FAR struct pollfd *fds, nfds_t nfds,
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FAR int *count, int ret)
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{
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unsigned int i;
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int status = OK;
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/* Process each descriptor in the list */
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*count = 0;
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for (i = 0; i < nfds; i++)
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{
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if (fds[i].fd >= 0)
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{
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status = poll_fdsetup(fds[i].fd, &fds[i], false);
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}
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if (status < 0)
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{
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ret = status;
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}
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/* Check if any events were posted */
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if (fds[i].revents != 0)
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{
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(*count)++;
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}
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/* Un-initialize the poll structure */
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fds[i].arg = NULL;
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fds[i].cb = NULL;
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}
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return ret;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: poll_fdsetup
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*
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* Description:
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* Configure (or unconfigure) one file/socket descriptor for the poll
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* operation. If fds and sem are non-null, then the poll is being setup.
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* if fds and sem are NULL, then the poll is being torn down.
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*
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****************************************************************************/
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int poll_fdsetup(int fd, FAR struct pollfd *fds, bool setup)
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{
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FAR struct file *filep;
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int ret;
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/* Get the file pointer corresponding to this file descriptor */
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ret = fs_getfilep(fd, &filep);
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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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DEBUGASSERT(filep != NULL);
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/* Let file_poll() do the rest */
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return file_poll(filep, fds, setup);
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}
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/****************************************************************************
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* Name: poll_default_cb
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*
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* Description:
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* The default poll callback function, this function do the final step of
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* poll notification.
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*
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* Input Parameters:
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* fds - The fds
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void poll_default_cb(FAR struct pollfd *fds)
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{
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int semcount = 0;
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FAR sem_t *pollsem;
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if (fds->arg != NULL)
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{
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pollsem = (FAR sem_t *)fds->arg;
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nxsem_get_value(pollsem, &semcount);
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if (semcount < 1)
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{
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nxsem_post(pollsem);
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}
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}
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}
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/****************************************************************************
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* Name: poll_notify
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*
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* Description:
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* Notify the poll, this function should be called by drivers to notify
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* the caller the poll is ready.
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*
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* Input Parameters:
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* afds - The fds array
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* nfds - Number of fds array
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* eventset - List of events to check for activity
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void poll_notify(FAR struct pollfd **afds, int nfds, pollevent_t eventset)
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{
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int i;
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FAR struct pollfd *fds;
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DEBUGASSERT(afds != NULL && nfds >= 1);
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for (i = 0; i < nfds && eventset; i++)
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{
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fds = afds[i];
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if (fds != NULL)
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{
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/* The error event must be set in fds->revents */
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fds->revents |= eventset & (fds->events | POLLERR | POLLHUP);
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if ((fds->revents & (POLLERR | POLLHUP)) != 0)
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{
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/* Error or Hung up, clear POLLOUT event */
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fds->revents &= ~POLLOUT;
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}
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if (fds->revents != 0 && fds->cb != NULL)
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{
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finfo("Report events: %08" PRIx32 "\n", fds->revents);
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fds->cb(fds);
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}
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}
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}
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}
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/****************************************************************************
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* Name: file_poll
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*
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* Description:
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* Low-level poll operation based on struct file. This is used both to (1)
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* support detached file, and also (2) by poll_fdsetup() to perform all
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* normal operations on file descriptors.
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*
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* Input Parameters:
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* file File structure instance
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* fds - The structure describing the events to be monitored, OR NULL if
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* this is a request to stop monitoring events.
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* setup - true: Setup up the poll; false: Teardown the poll
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*
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* Returned Value:
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* 0: Success; Negated errno on failure
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*
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****************************************************************************/
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int file_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
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{
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FAR struct inode *inode;
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int ret = -ENOSYS;
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DEBUGASSERT(filep != NULL);
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inode = filep->f_inode;
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if (inode != NULL)
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{
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/* Is a driver registered? Does it support the poll method?
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* If not, return -ENOSYS
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*/
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if ((INODE_IS_DRIVER(inode) || INODE_IS_MQUEUE(inode) ||
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INODE_IS_SOCKET(inode)) &&
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inode->u.i_ops != NULL && inode->u.i_ops->poll != NULL)
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{
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/* Yes, it does... Setup the poll */
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ret = (int)inode->u.i_ops->poll(filep, fds, setup);
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}
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/* Regular files (and block devices) are always readable and
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* writable. Open Group: "Regular files shall always poll TRUE for
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* reading and writing."
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*/
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if (INODE_IS_MOUNTPT(inode) || INODE_IS_BLOCK(inode) ||
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INODE_IS_MTD(inode))
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{
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if (setup)
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{
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poll_notify(&fds, 1, POLLIN | POLLOUT);
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}
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ret = OK;
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}
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}
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else
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{
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poll_notify(&fds, 1, POLLERR | POLLHUP);
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ret = OK;
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}
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return ret;
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}
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/****************************************************************************
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* Name: poll
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*
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* Description:
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* poll() waits for one of a set of file descriptors to become ready to
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* perform I/O. If none of the events requested (and no error) has
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* occurred for any of the file descriptors, then poll() blocks until
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* one of the events occurs.
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*
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* Input Parameters:
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* fds - List of structures describing file descriptors to be monitored
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* nfds - The number of entries in the list
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* timeout - Specifies an upper limit on the time for which poll() will
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* block in milliseconds. A negative value of timeout means an infinite
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* timeout.
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*
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* Returned Value:
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* On success, the number of structures that have non-zero revents fields.
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* A value of 0 indicates that the call timed out and no file descriptors
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* were ready. On error, -1 is returned, and errno is set appropriately:
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*
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* EBADF - An invalid file descriptor was given in one of the sets.
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* EFAULT - The fds address is invalid
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* EINTR - A signal occurred before any requested event.
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* EINVAL - The nfds value exceeds a system limit.
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* ENOMEM - There was no space to allocate internal data structures.
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* ENOSYS - One or more of the drivers supporting the file descriptor
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* does not support the poll method.
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*
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****************************************************************************/
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int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
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{
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FAR struct pollfd *kfds;
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sem_t sem;
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int count = 0;
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int ret2;
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int ret;
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DEBUGASSERT(nfds == 0 || fds != NULL);
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/* poll() is a cancellation point */
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enter_cancellation_point();
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#ifdef CONFIG_BUILD_KERNEL
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/* Allocate kernel memory for the fds */
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kfds = kmm_malloc(nfds * sizeof(struct pollfd));
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if (!kfds)
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{
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/* Out of memory */
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ret = -ENOMEM;
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goto out_with_cancelpt;
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}
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/* Copy the user fds to neutral kernel memory */
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memcpy(kfds, fds, nfds * sizeof(struct pollfd));
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#else
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/* Can use the user fds directly */
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kfds = fds;
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#endif
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nxsem_init(&sem, 0, 0);
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ret = poll_setup(kfds, nfds, &sem);
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if (ret >= 0)
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{
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if (timeout == 0)
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{
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/* Poll returns immediately whether we have a poll event or not. */
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ret = OK;
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}
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else if (timeout > 0)
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{
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clock_t ticks;
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/* "Implementations may place limitations on the granularity of
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* timeout intervals. If the requested timeout interval requires
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* a finer granularity than the implementation supports, the
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* actual timeout interval will be rounded up to the next
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* supported value." -- opengroup.org
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*
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* Round timeout up to next full tick.
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*/
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#if (MSEC_PER_TICK * USEC_PER_MSEC) != USEC_PER_TICK && \
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defined(CONFIG_HAVE_LONG_LONG)
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ticks = (((unsigned long long)timeout * USEC_PER_MSEC) +
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(USEC_PER_TICK - 1)) /
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USEC_PER_TICK;
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#else
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ticks = ((unsigned int)timeout + (MSEC_PER_TICK - 1)) /
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MSEC_PER_TICK;
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#endif
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/* Either wait for either a poll event(s), for a signal to occur,
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* or for the specified timeout to elapse with no event.
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*
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* NOTE: If a poll event is pending (i.e., the semaphore has
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* already been incremented), nxsem_tickwait() will not wait, but
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* will return immediately.
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*/
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ret = nxsem_tickwait(&sem, ticks);
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if (ret < 0)
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{
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if (ret == -ETIMEDOUT)
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{
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/* Return zero (OK) in the event of a timeout */
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ret = OK;
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}
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/* EINTR is the only other error expected in normal operation */
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}
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}
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else
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{
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/* Wait for the poll event or signal with no timeout */
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ret = nxsem_wait(&sem);
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}
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/* Teardown the poll operation and get the count of events. Zero will
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* be returned in the case of a timeout.
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*
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* Preserve ret, if negative, since it holds the result of the wait.
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*/
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ret2 = poll_teardown(kfds, nfds, &count, ret);
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if (ret2 < 0 && ret >= 0)
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{
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ret = ret2;
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}
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}
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nxsem_destroy(&sem);
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#ifdef CONFIG_BUILD_KERNEL
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/* Copy the events back to user */
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if (ret == OK)
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{
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int i;
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for (i = 0; i < nfds; i++)
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{
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fds[i].revents = kfds[i].revents;
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}
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}
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/* Free the temporary buffer */
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kmm_free(kfds);
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out_with_cancelpt:
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#endif
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leave_cancellation_point();
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if (ret < 0)
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{
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set_errno(-ret);
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return ERROR;
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}
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else
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{
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return count;
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}
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}
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