142 lines
4.5 KiB
C
142 lines
4.5 KiB
C
/****************************************************************************
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* libs/libc/signal/sig_set.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 <signal.h>
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#include <assert.h>
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sigset
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*
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* Description:
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* The signal() function will modify signal dispositions. The 'signo'
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* argument specifies the signal. The 'func' argument specifies the
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* signal's disposition, which may be SIG_DFL, SIG_IGN, or the address
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* of a signal handler.
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*
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* The System V sigset function is very similar to the (obsolete) POSIX
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* signal() function except that it includes additional management of the
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* tasks' signal mask. This function is then simply a wrapper around
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* signal() with this additional signal mask logic added.
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*
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* - The sigset set function also accepts the SIG_HOLD value for 'func':
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* If 'func' is equal to SIG_HOLD, 'signo' will be added to the signal
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* mask of the calling process and 'signo's disposition will remain
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* unchanged.
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* - If 'func' is not equal to SIG_HOLD, 'signo' will be removed from the
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* signal mask of the calling process.
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*
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* Input Parameters:
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* signo - Identifies the signal to operate on
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* func - The new disposition of the signal
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*
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* Returned Value:
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* Upon successful completion, sigset() shall return SIG_HOLD if the
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* signal had been blocked and the signal's previous disposition if it had
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* not been blocked. Otherwise, SIG_ERR shall be returned and errno set to
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* indicate the error.
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*
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* Hmm.. this wording is not clear to me. I assume this to mean:
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*
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* if (func == SIG_HOLD)
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* {
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* Set mask
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* if (mask successfully set)
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* {
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* return SIG_HOLD
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* }
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* else
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* {
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* return SIG_ERR
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* }
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* else
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* {
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* Set disposition
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* if (disposition successfully set)
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* {
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* return old disposition
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* }
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* else
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* {
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* return SIG_ERR
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* }
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* }
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*
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* But you could also argue that the English means to return SIG_HOLD in
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* any case is the signal is blocked. And, in that case would you set the
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* disposition or not? Unclear.
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*
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****************************************************************************/
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_sa_handler_t sigset(int signo, _sa_handler_t func)
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{
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_sa_handler_t disposition;
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sigset_t set;
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int ret;
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DEBUGASSERT(GOOD_SIGNO(signo) && func != SIG_ERR);
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sigemptyset(&set);
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sigaddset(&set, signo);
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/* Check if we are being asked to block the signal */
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if (func == SIG_HOLD)
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{
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ret = sigprocmask(SIG_BLOCK, &set, NULL);
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disposition = ret < 0 ? SIG_ERR : SIG_HOLD;
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}
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/* No.. then signal can handle the other cases */
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else
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{
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/* Set the signal handler disposition */
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disposition = signal(signo, func);
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if (disposition != SIG_ERR)
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{
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/* And unblock the signal */
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ret = sigprocmask(SIG_UNBLOCK, &set, NULL);
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if (ret < 0)
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{
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/* Restore the original signal disposition and return and
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* error.
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*/
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signal(signo, disposition);
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disposition = SIG_ERR;
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}
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}
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}
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return disposition;
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}
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