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nuttx/sched/signal/sig_notifier.c

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/****************************************************************************
* sched/signal/sig_notifier.c
*
* Copyright (C) 2018 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* 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 <nuttx/config.h>
#include <sys/types.h>
#include <stdint.h>
#include <stdbool.h>
#include <unistd.h>
#include <sched.h>
#include <assert.h>
#include <nuttx/irq.h>
#include <nuttx/signal.h>
#include <nuttx/semaphore.h>
#include "signal/signal.h"
#ifdef CONFIG_SIG_NOTIFIER
/****************************************************************************
* Private Types
****************************************************************************/
/* This is the saved information for one notification */
struct nxsig_notifier_s
{
FAR struct nxsig_notifier_s *flink; /* Supports a singly linked list */
FAR void *qualifier; /* Event qualifier value */
uint8_t signo; /* The signal number for notification */
uint8_t evtype; /* See enum nxsig_evtype_e */
pid_t pid; /* The PID to be notified */
int16_t key; /* Unique ID for this notification */
};
/****************************************************************************
* Private Data
****************************************************************************/
/* This is a statically allocated pool of notification structures */
static struct nxsig_notifier_s g_notifier_pool[CONFIG_SIG_NOTIFIER_NWAITERS];
/* This is a list of free notification structures */
static FAR struct nxsig_notifier_s *g_notifier_free;
/* This is a singly linked list of pending notifications. When an event
* occurs available, *all* of the waiters for that event in this list will
* be signaled and the entry will be freed. If there are multiple waiters
* for some resource, then only the highest priority thread will get the
* resource. Lower priority threads will need to call nxsig_notifier_setup()
* once again.
*/
static FAR struct nxsig_notifier_s *g_notifier_pending;
/* This semaphore is used as mutex to enforce mutually exclusive access to
* the notification data structures.
*/
static sem_t g_notifier_sem;
/* Used for lookup key generation */
static uint16_t g_notifier_key;
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: nxsig_notifier_alloc
*
* Description:
* Allocate a notification structure by removing it from the free list.
*
****************************************************************************/
static FAR struct nxsig_notifier_s *nxsig_notifier_alloc(void)
{
FAR struct nxsig_notifier_s *notifier;
notifier = g_notifier_free;
if (notifier != NULL)
{
g_notifier_free = notifier->flink;
notifier->flink = NULL;
}
return notifier;
}
/****************************************************************************
* Name: nxsig_notifier_free
*
* Description:
* Free a notification structure by returning it to the head of the free
* list.
*
****************************************************************************/
static void nxsig_notifier_free(FAR struct nxsig_notifier_s *notifier)
{
notifier->flink = g_notifier_free;
g_notifier_free = notifier;
}
/****************************************************************************
* Name: nxsig_notifier_find
*
* Description:
* Given a unique key for notification, find the corresponding notification
* structure in the pending notification list.
*
****************************************************************************/
static FAR struct nxsig_notifier_s *
nxsig_notifier_find(int16_t key, FAR struct nxsig_notifier_s **pprev)
{
FAR struct nxsig_notifier_s *notifier;
FAR struct nxsig_notifier_s *prev;
/* Find the entry matching this key in the g_notifier_pending list. */
for (prev = NULL, notifier = g_notifier_pending;
notifier != NULL;
prev = notifier, notifier = notifier->flink)
{
/* Is this the one we were looking for? */
if (notifier->key == key)
{
/* Return the previous entry if so requested */
if (pprev != NULL)
{
*pprev = prev;
}
return notifier;
}
}
return NULL;
}
/****************************************************************************
* Name: nxsig_notifier_key
*
* Description:
* Generate a unique key for this notification.
*
****************************************************************************/
static int16_t nxsig_notifier_key(void)
{
int16_t key;
/* Loop until a unique key is generated */
do
{
if (g_notifier_key >= INT16_MAX)
{
g_notifier_key = 0;
}
key = (int16_t)++g_notifier_key;
}
while (nxsig_notifier_find(key, NULL) != NULL);
return key;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxsig_notifier_initialize
*
* Description:
* Set up the notification structure for normal operation.
*
****************************************************************************/
void nxsig_notifier_initialize(void)
{
int i;
/* Add each notification structure to the free list */
for (i = 0; i < CONFIG_SIG_NOTIFIER_NWAITERS; i++)
{
FAR struct nxsig_notifier_s *notifier = &g_notifier_pool[i];
/* Add the pre-allocated notification to the head of the free list */
notifier->flink = g_notifier_free;
g_notifier_free = notifier;
}
/* Initialize the semaphore that enforces mutually exclusive access to the
* notification data structures.
*/
nxsem_init(&g_notifier_sem, 0, 1);
}
/****************************************************************************
* Name: nxsig_notifier_setup
*
* Description:
* Set up to notify the specified PID with the provided signal number.
*
* NOTE: To avoid race conditions, the caller should set the sigprocmask
* to block signal delivery. The signal will be delivered once the
* signal is removed from the sigprocmask.
*
* NOTE: If sigwaitinfo() or sigtimedwait() are used to catch the signal
* then then qualifier value may be recovered in the sival_ptr value of
* the struct siginfo instance.
*
* Input Parameters:
* pid - The PID to be notified. If a zero value is provided,
* then the PID of the calling thread will be used.
* signo - The signal number to use with the notification.
* evtype - The event type.
* qualifier - Event qualifier to distinguish different cases of the
* generic event type.
*
* Returned Value:
* > 0 - The key which may be used later in a call to
* nxsig_notifier_teardown().
* == 0 - Not used (reserved for wrapper functions).
* < 0 - An unexpected error occurred and no signal will be sent. The
* returned value is a negated errno value that indicates the
* nature of the failure.
*
****************************************************************************/
int nxsig_notifier_setup(int pid, int signo, enum nxsig_evtype_e evtype,
FAR void *qualifier)
{
int ret;
/* If the 'pid' is zero, then use the PID of the calling thread */
if (pid <= 0)
{
pid = getpid();
}
/* Get exclusive access to the notifier data structures */
ret = nxsem_wait(&g_notifier_sem);
if (ret < 0)
{
return ret;
}
/* Allocate a new notification */
FAR struct nxsig_notifier_s *notifier = nxsig_notifier_alloc();
if (notifier == NULL)
{
ret = -ENOSPC;
}
else
{
/* Generate a unique key for this notification */
int16_t key = nxsig_notifier_key();
/* Initialize the notification structure */
notifier->pid = pid;
notifier->signo = signo;
notifier->evtype = evtype;
notifier->key = key;
notifier->qualifier = qualifier;
/* And add it to the head of the pending list */
notifier->flink = g_notifier_pending;
g_notifier_pending = notifier;
ret = key;
}
(void)nxsem_post(&g_notifier_sem);
return ret;
}
/****************************************************************************
* Name: nxsig_notifier_teardown
*
* Description:
* Eliminate a notification previously setup by nxsig_notifier_setup().
* This function should only be called if the notification should be
* aborted prior to the notification. The notification will automatically
* be torn down after the signal is sent.
*
* Input Parameters:
* key - The key value returned from a previous call to
* nxsig_notifier_setup().
*
* Returned Value:
* Zero (OK) is returned on success; a negated errno value is returned on
* any failure.
*
****************************************************************************/
int nxsig_notifier_teardown(int key)
{
FAR struct nxsig_notifier_s *notifier;
FAR struct nxsig_notifier_s *prev;
int ret;
/* Get exclusive access to the notifier data structures */
ret = nxsem_wait(&g_notifier_sem);
if (ret < 0)
{
return ret;
}
/* Find the entry matching this PID in the g_notifier_pending list. We
* assume that there is only one.
*/
notifier = nxsig_notifier_find(key, &prev);
if (notifier == NULL)
{
/* There is no notification with this key in the pending list */
ret = -ENOENT;
}
else
{
/* Found it! Remove the notification from the pending list */
if (prev == NULL)
{
g_notifier_pending = notifier->flink;
}
else
{
prev->flink = notifier->flink;
}
/* And add it to the free list */
nxsig_notifier_free(notifier);
ret = OK;
}
(void)nxsem_post(&g_notifier_sem);
return ret;
}
/****************************************************************************
* Name: nxsig_notifier_signal
*
* Description:
* An event has just occurred. Signal all threads waiting for that event.
*
* When an IOB becomes available, *all* of the waiters in this thread will
* be signaled. If there are multiple waiters for a resource then only
* the highest priority thread will get the resource. Lower priority
* threads will need to call nxsig_notify once again.
*
* NOTE: If sigwaitinfo() or sigtimedwait() are used to catch the signal
* then then qualifier value may be obtained in the sival_ptr value of
* the struct siginfo instance.
*
* Input Parameters:
* evtype - The type of the event that just occurred.
* qualifier - Event qualifier to distinguish different cases of the
* generic event type.
*
* Returned Value:
* None.
*
****************************************************************************/
void nxsig_notifier_signal(enum nxsig_evtype_e evtype,
FAR void *qualifier)
{
FAR struct nxsig_notifier_s *notifier;
FAR struct nxsig_notifier_s *prev;
FAR struct nxsig_notifier_s *next;
int ret;
/* Get exclusive access to the notifier data structure */
ret = nxsem_wait(&g_notifier_sem);
while (ret < 0)
{
DEBUGASSERT(ret == -EINTR || ret == -ECANCELED);
}
/* Don't let any newly started threads block this thread until all of
* the notifications and been sent.
*/
sched_lock();
/* Process the notification at the head of the pending list until the
* pending list is empty */
/* Find the entry matching this key in the g_notifier_pending list. */
for (prev = NULL, notifier = g_notifier_pending;
notifier != NULL;
notifier = next)
{
#ifdef CONFIG_CAN_PASS_STRUCTS
union sigval value;
#endif
/* Set up for the next time through the loop (in case the entry is
* removed from the list).
*/
next = notifier->flink;
/* Check if this is the a notification request for the event that
* just occurred.
*/
if (notifier->evtype == evtype && notifier->qualifier == qualifier)
{
/* Yes.. Remove the notification from the pending list */
if (prev == NULL)
{
g_notifier_pending = next;
}
else
{
prev->flink = next;
}
/* Signal the waiter */
#ifdef CONFIG_CAN_PASS_STRUCTS
value.sival_ptr = notifier->qualifier;
(void)nxsig_queue(notifier->pid, notifier->signo, value);
#else
(void)nxsig_queue(notifier->pid, notifier->signo,
notifier->qualifier);
#endif
/* Free the notification by returning it to the free list */
nxsig_notifier_free(notifier);
}
else
{
/* The entry was not removed, the current entry will be the
* next previous entry.
*/
prev = notifier;
}
}
sched_unlock();
(void)nxsem_post(&g_notifier_sem);
}
#endif /* CONFIG_SIG_NOTIFIER */
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