Signals: Correct implementation of sigset(). It is not just signal() with a different name; it has some additional signal mask handling functionality

libc/signal/Make.defs

@@ -1,7 +1,7 @@
 ############################################################################
 # libc/signal/Make.defs
 #
-#   Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2011-2012, 2016 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -39,7 +39,7 @@ ifneq ($(CONFIG_DISABLE_SIGNALS),y)
 
 CSRCS += sig_emptyset.c sig_fillset.c sig_addset.c sig_delset.c
 CSRCS += sig_ismember.c sig_hold.c sig_relse.c sig_ignore.c sig_pause.c
-CSRCS += signal.c
+CSRCS += sig_set.c signal.c
 
 # Add the signal directory to the build
 

libc/signal/sig_fillset.c

@@ -39,26 +39,6 @@
 
 #include <signal.h>
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Type Declarations
- ****************************************************************************/
-
-/****************************************************************************
- * Public Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Function Prototypes
- ****************************************************************************/
-
 /****************************************************************************
  * Publics Functions
  ****************************************************************************/

libc/signal/sig_ismember.c

@@ -39,26 +39,6 @@
 
 #include <signal.h>
 
-/****************************************************************************
- * Pre-processor Definitions
- ****************************************************************************/
-
-/****************************************************************************
- * Private Type Declarations
- ****************************************************************************/
-
-/****************************************************************************
- * Public Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Function Prototypes
- ****************************************************************************/
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/

libc/signal/sig_relse.c

@@ -47,8 +47,8 @@
  * Name: sigrelse
  *
  * Description:
- *   The sigrelse() function will remove 'signo' to the calling process' signal
- *   mask.
+ *   The sigrelse() function will remove 'signo' from the calling process'
+ *   signal mask.
  *
  ****************************************************************************/
 

libc/signal/sig_set.c

@@ -0,0 +1,156 @@
+/****************************************************************************
+ * libc/signal/sig_set.c
+ *
+ *   Copyright (C) 2015-2016 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 <signal.h>
+#include <assert.h>
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: sigset
+ *
+ * Description:
+ *   The signal() function will modify signal dispositions. The 'signo'
+ *   argument specifies the signal. The 'func' argument specifies the
+ *   signal's disposition, which may be SIG_DFL, SIG_IGN, or the address
+ *   of a signal handler.
+ *
+ *   The System V sigset function is very similar to the (obsolete) POSIX
+ *   signal() function except that it includes additional managment of the
+ *   tasks' signal mask.  This function is then simply a wrapper around
+ *   signal() with this additional signal mask logic added.
+ *
+ *   - The sigset set function also accepts the SIG_HOLD value for 'func':
+ *     If 'func' is equal to SIG_HOLD, 'signo' will be added to the signal
+ *     mask of the calling process and 'signo's disposition will remain
+ *     unchanged.
+ *   - If 'func' is not equal to SIG_HOLD, 'signo' will be removed from the
+ *     signal mask of the calling process.
+ *
+ * Input Parameters:
+ *   signo - Identifies the signal to operate on
+ *   func  - The new disposition of the signal
+ *
+ * Returned Value:
+ *   Upon successful completion, sigset() shall return SIG_HOLD if the
+ *   signal had been blocked and the signal's previous disposition if it had
+ *   not been blocked. Otherwise, SIG_ERR shall be returned and errno set to
+ *   indicate the error.
+ *
+ *   Hmm.. this wording is not clear to me.  I assume this to mean:
+ *
+ *     if (func == SIG_HOLD)
+ *       {
+ *          Set mask
+ *          if (mask successfuly set)
+ *            {
+ *              return SIG_HOLD
+ *            }
+ *          else
+ *            {
+ *              return SIG_ERR
+ *            }
+ *     else
+ *       {
+ *         Set disposition
+ *          if (disposition successfuly set)
+ *            {
+ *              return old disposition
+ *            }
+ *          else
+ *            {
+ *              return SIG_ERR
+ *            }
+ *       }
+ *
+ *   But you could also argue that the English means to return SIG_HOLD in
+ *   any case is the signal is blocked.  And, in that case would you set the
+ *   disposition or not?  Unclear.
+ *
+ ****************************************************************************/
+
+CODE void (*sigset(int signo, CODE void (*func)(int signo)))(int signo)
+{
+  _sa_handler_t disposition;
+  sigset_t set;
+  int ret;
+
+  DEBUGASSERT(GOOD_SIGNO(signo) && func != NULL);
+
+  (void)sigemptyset(&set);
+  (void)sigaddset(&set, signo);
+
+  /* Check if we are being asked to block the signal */
+
+  if (func == SIG_HOLD)
+    {
+      ret = sigprocmask(SIG_BLOCK, &set, NULL);
+      disposition = ret < 0 ? SIG_ERR : SIG_HOLD;
+    }
+
+  /* No.. then signal can handle the other cases */
+
+  else
+    {
+      /* Set the signal handler disposition */
+
+      disposition = signal(signo, func);
+      if (disposition != SIG_ERR)
+        {
+          /* And unblock the signal */
+
+          ret = sigprocmask(SIG_UNBLOCK, &set, NULL);
+          if (ret < 0)
+            {
+              /* Restore the original signal disposition and return and
+               * error.
+               */
+
+              (void)signal(signo, disposition);
+              disposition = SIG_ERR;
+            }
+        }
+    }
+
+  return disposition;
+}

libc/signal/signal.c

@@ -37,7 +37,10 @@
  * Included Files
  ****************************************************************************/
 
+#include <nuttx/config.h>
+
 #include <signal.h>
+#include <assert.h>
 
 /****************************************************************************
  * Public Functions
@@ -50,29 +53,20 @@
  *   The signal() function will modify signal dispositions. The 'signo'
  *   argument specifies the signal. The 'func' argument specifies the
  *   signal's disposition, which may be SIG_DFL, SIG_IGN, or the address
- *   of a signal handler. If 'func' is the address of a signal handler, the
+ *   of a signal handler.  If 'func' is the address of a signal handler, the
  *   system will add 'signo' to the calling process' signal mask before
  *   executing the signal handler; when the signal handler returns, the
  *   system will restore the calling process' signal mask to its state prior
- *   to the delivery of the signal.  'signo' will be removed from the calling
- *   process' signal mask.
- *
- *   NOTE:  The value SIG_HOLD for 'func' is not supported.  It should work
- *   like this:  If 'func' is equal to SIG_HOLD, 'signo' will be added to,
- *   not removed from, the calling process' signal mask and 'signo''s
- *   disposition will remain unchanged.
+ *   to the delivery of the signal.
  *
  * Input Parameters:
  *   signo - Identifies the signal to operate on
  *   func  - The new disposition of the signal
  *
  * Returned Value:
- *   Upon successful completion, signal() will the previous disposition of
- *   the signal. Otherwise, SIG_ERR will be returned and errno set to
- *   indicate the error.
- *
- *   NOTE: signal() would return SIG_HOLD if the signal had been blocked and
- *   the signal's previous disposition if it had not been blocked.
+ *   Upon successful completion, signal() will return the previous
+ *   disposition of the signal handling. Otherwise, SIG_ERR will be returned
+ *   and errno set to indicate the nature of the error.
  *
  ****************************************************************************/
 
@@ -82,6 +76,9 @@ CODE void (*signal(int signo, CODE void (*func)(int signo)))(int signo)
   struct sigaction oact;
   int ret;
 
+  DEBUGASSERT(GOOD_SIGNO(signo) && func != NULL);
+  DEBUGASSERT(func != SIG_ERR && func != SIG_HOLD);
+
   /* Initialize the sigaction structure */
 
   act.sa_handler = func;