138 lines
4.6 KiB
C
138 lines
4.6 KiB
C
/****************************************************************************
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* sched/signal/sig_pselect.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 <sys/select.h>
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#include <sys/time.h>
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#include "sched/sched.h"
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#include "signal/signal.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: pselect
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*
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* Description:
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* pselect() allows a program to monitor multiple file descriptors, waiting
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* until one or more of the file descriptors become "ready" for some class
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* of I/O operation (e.g., input possible). A file descriptor is
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* considered ready if it is possible to perform the corresponding I/O
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* operation (e.g., read(2)) without blocking.
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*
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* Input Parameters:
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* nfds - the maximum fd number (+1) of any descriptor in any of the
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* three sets.
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* readfds - the set of descriptions to monitor for read-ready events
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* writefds - the set of descriptions to monitor for write-ready events
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* exceptfds - the set of descriptions to monitor for error events
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* timeout - Return at this time if none of these events of interest
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* occur.
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* sigmask - Replace the current signal mask temporarily during execution
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*
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* Returned Value:
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* 0: Timer expired
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* >0: The number of bits set in the three sets of descriptors
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* -1: An error occurred (errno will be set appropriately)
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*
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****************************************************************************/
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int pselect(int nfds, FAR fd_set *readfds, FAR fd_set *writefds,
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FAR fd_set *exceptfds, FAR const struct timespec *timeout,
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FAR const sigset_t *sigmask)
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{
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FAR struct tcb_s *rtcb = this_task();
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sigset_t saved_sigprocmask;
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irqstate_t flags;
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int ret = ERROR;
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/* Several operations must be performed below: We must determine if any
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* signal is pending and, if not, wait for the signal. Since signals can
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* be posted from the interrupt level, there is a race condition that
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* can only be eliminated by disabling interrupts!
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*/
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flags = enter_critical_section();
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/* Save a copy of the old sigprocmask and install
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* the new (temporary) sigprocmask
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*/
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saved_sigprocmask = rtcb->sigprocmask;
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if (sigmask)
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{
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rtcb->sigprocmask = *sigmask;
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}
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sigemptyset(&rtcb->sigwaitmask);
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/* Check if there is a pending signal corresponding to one of the
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* signals that will be unblocked by the new sigprocmask.
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*/
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if (nxsig_unmask_pendingsignal())
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{
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/* Dispatching one or more of the signals is sufficient to cause
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* us to not wait. Restore the original sigprocmask.
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*/
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rtcb->sigprocmask = saved_sigprocmask;
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leave_critical_section(flags);
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set_errno(EINTR);
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}
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else
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{
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FAR struct timeval *timeval = NULL;
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struct timeval timeval_buf;
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/* And call select to do the real work */
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if (timeout)
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{
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timeval_buf.tv_sec = timeout->tv_sec;
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timeval_buf.tv_usec = timeout->tv_nsec / 1000;
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timeval = &timeval_buf;
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}
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ret = select(nfds, readfds, writefds, exceptfds, timeval);
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/* We are running again, restore the original sigprocmask */
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rtcb->sigprocmask = saved_sigprocmask;
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leave_critical_section(flags);
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/* Now, handle the (rare?) case where (a) a blocked signal was received
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* while the task was suspended but (b) restoring the original
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* sigprocmask will unblock the signal.
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*/
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nxsig_unmask_pendingsignal();
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}
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return ret;
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}
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