sched/signal: In signal notification facility, use sigqueue() to notify vs. kill(). With sigqueue, we can pass more info (but still not enough).

include/nuttx/signal.h

@@ -481,6 +481,10 @@ int nxsig_evthread(pid_t pid, FAR struct sigevent *event);
  *   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.
@@ -538,6 +542,10 @@ int nxsig_notifier_teardown(int key);
  *   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

net/netdev/netdown_notifier.c

@@ -0,0 +1,153 @@
+/****************************************************************************
+ * net/netdev/netdown_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 <nuttx/signal.h>
+#include <nuttx/mm/iob.h>
+#include <nuttx/net/netdev.h>
+
+#include "netdev/netdev.h"
+
+#ifdef CONFIG_NETDOWN_NOTIFIER
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: netdown_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.
+ *
+ * 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.
+ *   dev   - The network driver to be monitored
+ *
+ * Returned Value:
+ *   > 0   - The signal notification is in place.  The returned value is a
+ *           key that may be used later in a call to
+ *           netdown_notifier_teardown().
+ *   == 0  - The the device is already down.  No signal notification will
+ *           be provided.
+ *   < 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 netdown_notifier_setup(int pid, int signo, FAR struct net_driver_s *dev)
+{
+  /* If network driver is already down, then return zero without setting up
+   * the notification.
+   */
+
+  if ((dev->d_flags & IFF_UP) == 0)
+    {
+      return 0;
+    }
+
+  /* Otherwise, this is just a simple wrapper around nxsig_notifer_setup(). */
+
+  return nxsig_notifier_setup(pid, signo, NXSIG_NET_DOWN, dev);
+}
+
+/****************************************************************************
+ * Name: netdown_notifier_teardown
+ *
+ * Description:
+ *   Eliminate a TCP read-ahead notification previously setup by
+ *   netdown_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
+ *         netdown_notifier_setup().
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; a negated errno value is returned on
+ *   any failure.
+ *
+ ****************************************************************************/
+
+int netdown_notifier_teardown(int key)
+{
+  /* This is just a simple wrapper around nxsig_notifier_teardown(). */
+
+  return nxsig_notifier_teardown(key);
+}
+
+/****************************************************************************
+ * Name: netdown_notifier_signal
+ *
+ * Description:
+ *   Read-ahead data has been buffered.  Signal all threads waiting for
+ *   read-ahead data to become available.
+ *
+ *   When the read-ahead data becomes available, *all* of the waiters in
+ *   this thread will be signaled.  If there are multiple waiters then only
+ *   the highest priority thread will get the data.  Lower priority threads
+ *   will need to call netdown_notifier_setup() once again.
+ *
+ * Input Parameters:
+ *   dev  - The TCP connection where read-ahead data was just buffered.
+ *
+ * Returned Value:
+ *   None.
+ *
+ ****************************************************************************/
+
+void netdown_notifier_signal(FAR struct net_driver_s *dev)
+{
+  /* This is just a simple wrapper around nxsig_notifier_signal(). */
+
+  return nxsig_notifier_signal(NXSIG_NET_DOWN, dev);
+}
+
+#endif /* CONFIG_NETDOWN_NOTIFIER */

net/tcp/tcp.h

@@ -1552,6 +1552,10 @@ int tcp_pollteardown(FAR struct socket *psock, FAR struct pollfd *fds);
  *   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 TCP connection structure pointer 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.
@@ -1609,6 +1613,10 @@ int tcp_notifier_teardown(int key);
  *   the highest priority thread will get the data.  Lower priority threads
  *   will need to call tcp_notifier_setup() once again.
  *
+ *   NOTE: If sigwaitinfo() or sigtimedwait() are used to catch the signal
+ *   then then TCP connection structure pointer may be obtained in the
+ *   sival_ptr value of the struct siginfo instance.
+ *
  * Input Parameters:
  *   conn  - The TCP connection where read-ahead data was just buffered.
  *

net/tcp/tcp_notifier.c

@@ -62,6 +62,10 @@
  *   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 TCP connection structure pointer 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.
@@ -134,6 +138,10 @@ int tcp_notifier_teardown(int key)
  *   the highest priority thread will get the data.  Lower priority threads
  *   will need to call tcp_notifier_setup() once again.
  *
+ *   NOTE: If sigwaitinfo() or sigtimedwait() are used to catch the signal
+ *   then then TCP connection structure pointer may be obtained in the
+ *   sival_ptr value of the struct siginfo instance.
+ *
  * Input Parameters:
  *   conn  - The TCP connection where read-ahead data was just buffered.
  *

net/udp/udp.h

@@ -653,6 +653,10 @@ int udp_pollteardown(FAR struct socket *psock, FAR struct pollfd *fds);
  *   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 UDP connection structure pointer 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.
@@ -710,6 +714,10 @@ int udp_notifier_teardown(int key);
  *   the highest priority thread will get the data.  Lower priority threads
  *   will need to call udp_notifier_setup() once again.
  *
+ *   NOTE: If sigwaitinfo() or sigtimedwait() are used to catch the signal
+ *   then then UDP connection structure pointer may be obtained in the
+ *   sival_ptr value of the struct siginfo instance.
+ *
  * Input Parameters:
  *   conn  - The UDP connection where read-ahead data was just buffered.
  *

net/udp/udp_notifier.c

@@ -62,6 +62,10 @@
  *   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 UDP connection structure pointer 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.
@@ -134,6 +138,10 @@ int udp_notifier_teardown(int key)
  *   the highest priority thread will get the data.  Lower priority threads
  *   will need to call udp_notifier_setup() once again.
  *
+ *   NOTE: If sigwaitinfo() or sigtimedwait() are used to catch the signal
+ *   then then UDP connection structure pointer may be obtained in the
+ *   sival_ptr value of the struct siginfo instance.
+ *
  * Input Parameters:
  *   conn  - The UDP connection where read-ahead data was just buffered.
  *

sched/signal/sig_notifier.c

@@ -255,6 +255,10 @@ void nxsig_notifier_initialize(void)
  *   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.
@@ -403,6 +407,10 @@ int nxsig_notifier_teardown(int key)
  *   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
@@ -444,6 +452,10 @@ void nxsig_notifier_signal(enum nxsig_evtype_e evtype,
        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).
        */
@@ -469,8 +481,13 @@ void nxsig_notifier_signal(enum nxsig_evtype_e evtype,
 
           /* Signal the waiter */
 
-          (void)nxsig_kill(notifier->pid, notifier->signo);
+#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);