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/****************************************************************************
* sig_suspend.c
*
* Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <sys/types.h>
#include <signal.h>
#include <assert.h>
#include <debug.h>
#include <sched.h>
#include <nuttx/arch.h>
#include "os_internal.h"
#include "sig_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Function: sigsuspend
*
* Description:
*
* The sigsuspend() function replaces the signal mask of the task with the
* set of signals pointed to by the argument 'set' and then suspends the
* process until delivery of a signal to the task.
*
* If the effect of the set argument is to unblock a pending signal, then
* no wait is performed.
*
* The original signal mask is restored when this function returns.
*
* Waiting for an empty signal set stops a task without freeing any
* resources.
*
* Parameters:
* set - signal mask to use while suspended.
*
* Return Value:
* -1 (ERROR) always
*
* Assumptions:
*
* POSIX Compatibility:
* int sigsuspend(const sigset_t *set);
*
* POSIX states that sigsuspend() "suspends the process until delivery of
* a signal whose action is either to execute a signal-catching function
* or to terminate the process." Only the deliver of a signal is required
* in the present implementation (even if the signal is ignored).
*
****************************************************************************/
int sigsuspend(FAR const sigset_t *set)
{
FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
sigset_t intersection;
sigset_t saved_sigprocmask;
FAR sigpendq_t *sigpend;
irqstate_t saved_state;
int unblocksigno;
/* Several operations must be performed below: We must determine if any
* signal is pending and, if not, wait for the signal. Since signals can
* be posted from the interrupt level, there is a race condition that
* can only be eliminated by disabling interrupts!
*/
sched_lock(); /* Not necessary */
saved_state = irqsave();
/* Check if there is a pending signal corresponding to one of the
* signals that will be unblocked by the new sigprocmask.
*/
intersection = ~(*set) & sig_pendingset(rtcb);
if (intersection != NULL_SIGNAL_SET)
{
/* One or more of the signals in intersections is sufficient to cause
* us to not wait. Pick the lowest numbered signal and mark it not
* pending.
*/
unblocksigno = sig_lowest(&intersection);
sigpend = sig_removependingsignal(rtcb, unblocksigno);
if (!sigpend)
{
PANIC(OSERR_FAILEDTOREMOVESIGNAL);
}
sig_releasependingsignal(sigpend);
irqrestore(saved_state);
}
else
{
/* Its time to wait. Save a copy of the old sigprocmask and install
* the new (temporary) sigprocmask
*/
saved_sigprocmask = rtcb->sigprocmask;
rtcb->sigprocmask = *set;
rtcb->sigwaitmask = NULL_SIGNAL_SET;
/* And wait until one of the unblocked signals is posted */
up_block_task(rtcb, TSTATE_WAIT_SIG);
/* We are running again, restore the original sigprocmask */
rtcb->sigprocmask = saved_sigprocmask;
irqrestore(saved_state);
/* Now, handle the (rare?) case where (a) a blocked signal was received
* while the task was suspended but (b) restoring the original
* sigprocmask will unblock the signal.
*/
sig_unmaskpendingsignal();
}
sched_unlock();
return ERROR;
}
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