Add VFS-based sem_open() implementation

fs/Makefile

@@ -49,6 +49,10 @@ include driver/Make.defs
 include dirent/Make.defs
 include mmap/Make.defs
 
+# OS resources
+
+include semaphore/Make.defs
+
 # Additional files required is mount-able file systems are supported
 
 ifneq ($(CONFIG_NFILE_DESCRIPTORS),0)

fs/semaphore/Make.defs

@@ -37,6 +37,8 @@
 
 ifneq ($(CONFIG_FS_NAMED_SEMAPHORES),0)
 
+CSRCS += sem_open.c
+
 # Include named semaphore build support
 
 DEPPATH += --dep-path semaphore

fs/semaphore/sem_open.c

@@ -0,0 +1,266 @@
+/****************************************************************************
+ * fs/semaphore/sem_open.c
+ *
+ *   Copyright (C) 2014 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 <stdint.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <fcntl.h>
+#include <semaphore.h>
+#include <string.h>
+#include <sched.h>
+#include <errno.h>
+
+#include <nuttx/kmalloc.h>
+#include <nuttx/semaphore.h>
+#include <nuttx/fs/fs.h>
+
+#include "fs.h"
+
+#ifdef CONFIG_FS_NAMED_SEMAPHORES
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define MAX_SEMPATH 64
+
+/****************************************************************************
+ * Private Type Declarations
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Variables
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: sem_open
+ *
+ * Description:
+ *   This function establishes a connection between named semaphores and a
+ *   task.  Following a call to sem_open() with the semaphore name, the task
+ *   may reference the semaphore associated with name using the address
+ *   returned by this call.  The semaphore may be used in subsequent calls
+ *   to sem_wait(), sem_trywait(), and sem_post().  The semaphore remains
+ *   usable until the semaphore is closed by a successful call to sem_close().
+ *
+ *   If a task makes multiple calls to sem_open() with the same name, then
+ *   the same semaphore address is returned (provided there have been no
+ *   calls to sem_unlink()).
+ *
+ * Parameters:
+ *   name  - Semaphore name
+ *   oflags - Semaphore creation options.  This may either or both of the
+ *     following bit settings.
+ *     oflags = 0:  Connect to the semaphore only if it already exists.
+ *     oflags = O_CREAT:  Connect to the semaphore if it exists, otherwise
+ *        create the semaphore.
+ *     oflags = O_CREAT|O_EXCL:  Create a new semaphore
+ *        unless one of this name already exists.
+ *   Optional parameters.  When the O_CREAT flag is specified, two optional
+ *     parameters are expected:
+ *     1. mode_t mode (ignored), and
+ *     2. unsigned int value.  This initial value of the semaphore. Valid
+ *        initial values of the semaphore must be less than or equal to
+ *        SEM_VALUE_MAX.
+ *
+ * Return Value:
+ *   A pointer to sem_t or -1 (ERROR) if unsuccessful.
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+FAR sem_t *sem_open (FAR const char *name, int oflags, ...)
+{
+  FAR struct filelist *list;
+  FAR struct inode *inode;
+  FAR const char *relpath = NULL;
+  mode_t mode;
+  FAR struct nsem_inode_s *nsem;
+  FAR sem_t *sem = (FAR sem_t*)ERROR;
+  char fullpath[MAX_SEMPATH];
+  unsigned value;
+  int errcode;
+  int ret;
+
+  /* Make sure that a non-NULL name is supplied */
+
+  if (name)
+    {
+      /* The POSIX specification requires that the "check for the existence
+       * of a semaphore and the creation of the semaphore if it does not 
+       * exist shall be atomic with respect to other processes executing
+       * sem_open()..."  A simple sched_lock() should be sufficient to meet
+       * this requirement.
+       */
+
+      sched_lock();
+
+      /* Get the full path to the semaphore */
+
+      snprintf(fullpath, MAX_SEMPATH, CONFIG_FS_NAMED_SEMPATH "/%s", name);
+
+      /* Get the thread-specific file list */
+
+      list = sched_getfiles();
+      DEBUGASSERT(list);
+
+      /* Get the inode for this file.  This should succeed if the semaphore
+       * has already been created.
+       */
+
+      inode = inode_find(fullpath, &relpath);
+      if (inode)
+        {
+          /* It exists.  Verify that the inode is a semaphore */
+
+          if (!INODE_IS_NAMEDSEM(inode))
+            {
+              errcode = ENXIO;
+              goto errout_with_inode;
+            }
+
+          /* It exists and is a semaphore.  Check if the caller wanted to
+           * create a new semaphore with this name.
+           */
+
+          if ((oflags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
+            {
+              errcode = EEXIST;
+              goto errout_with_inode;
+            }
+
+          /* Allow a new connection to the semaphore */
+
+          nsem = inode->u.i_nsem;
+          nsem->ns_refs++;
+          sem  = &nsem->ns_sem;
+
+        }
+      else
+        {
+          va_list ap;
+
+          /* The semaphore does not exists.  Were we asked to create it? */
+
+          if ((oflags & O_CREAT) == 0)
+            {
+              /* The semaphore does not exist and O_CREAT is not set */
+
+              errcode = ENOENT;
+              goto errout_with_lock;
+            }
+
+         /* Create the semaphore.  First we have to extract the additional
+          * parameters from the variable argument list.
+          * REVISIT:  Mode parameter is not currently used.
+          */
+
+          va_start(ap, oflags);
+          mode  = va_arg(ap, mode_t);
+          value = va_arg(ap, unsigned);
+          va_end(ap);
+
+          UNUSED(mode);
+
+          /* Check the semaphore value */
+
+          if (value > SEM_VALUE_MAX)
+            {
+              errcode = EINVAL;
+              goto errout_with_lock;
+            }
+
+          /* Create an inode in the pseudo-filesystem at this path */
+
+          inode_semtake();
+          ret = inode_reserve(fullpath, &inode);
+          inode_semgive();
+
+          if (ret < 0)
+            {
+              errcode = -ret;
+              goto errout_with_lock;
+            }
+
+          /* Allocate the semaphore structure (using the appropriate allocator
+           * for the group)
+           */
+
+          nsem = group_malloc(NULL, sizeof(struct nsem_inode_s));
+          if (!nsem)
+            {
+              errcode = ENOMEM;
+              goto errout_with_lock;
+            }
+
+          /* Initialize the semaphore */
+
+          inode->u.i_nsem = nsem;
+          nsem->ns_refs   = 1;
+          sem             = &nsem->ns_sem;
+        }
+    }
+
+  sched_unlock();
+  return sem;
+
+ errout_with_inode:
+  inode_release(inode);
+ errout_with_lock:
+  sched_unlock();
+  set_errno(errcode);
+  return (FAR sem_t *)ERROR;
+}
+
+#endif /* CONFIG_FS_NAMED_SEMAPHORES */

include/nuttx/fs/fs.h

@@ -209,21 +209,9 @@ struct mountpt_operations
  *   - Shared memory:        shm_open() and shm_unlink();
  *
  * These are a special case in that they do not follow quite the same
- * pattern as the other file system types in that they have no read or
- * write methods.
- *
- * Each inode type carries a payload specific to the OS resource;
- * Only the contents of struct special_operations is visible to the VFS.
+ * pattern as the other file system types in that they have operations.
  */
 
-struct inode;
-struct special_operations
-{
-  int     (*open)(FAR struct inode *inode);
-  int     (*close)(FAR struct inode *inode);
-  int     (*unlink)(FAR struct inode *inode, FAR const char *relpath);
-};
-
 /* These are the various kinds of operations that can be associated with
  * an inode.
  */
@@ -235,9 +223,8 @@ union inode_ops_u
   FAR const struct block_operations     *i_bops; /* Block driver operations */
   FAR const struct mountpt_operations   *i_mops; /* Operations on a mountpoint */
 #endif
-  FAR const struct special_operations   *i_xops; /* Generic operations on OS resources */
 #ifdef CONFIG_FS_NAMED_SEMAPHORES
-  FAR const struct semaphore_operations *i_sops; /* Operations for named semaphores */
+  FAR struct nsem_inode_s               *i_nsem; /* Named semaphore */
 #endif
 };
 

include/nuttx/semaphore.h

@@ -57,15 +57,8 @@
 #ifdef CONFIG_FS_NAMED_SEMAPHORES
 /* This is the named semaphore inode */
 
-struct inode; /* Forward reference */
-struct semaphore_operations
+struct nsem_inode_s
 {
-  /* Common inode operations */
-
-  int     (*open)(FAR struct inode *inode);
-  int     (*close)(FAR struct inode *inode);
-  int     (*unlink)(FAR struct inode *inode, FAR const char *relpath);
-
   /* Payload unique to named semaphores */
 
   uint16_t ns_refs;                 /* Number of open references semaphore */

sched/group/group_free.c

@@ -84,7 +84,14 @@
 
 void group_free(FAR struct task_group_s *group, FAR void *mem)
 {
-  DEBUGASSERT(group && mem);
+  /* A NULL group pointer means the current group */
+
+  if (!group)
+    {
+      FAR struct tcb_s *tcb = (FAR struct tcb_s *)g_readytorun.head;
+      DEBUGASSERT(tcb && tcb->group);
+      group = tcb->group;
+    }
 
   /* Check the group is privileged */
 

sched/group/group_malloc.c

@@ -87,7 +87,14 @@
 
 FAR void *group_malloc(FAR struct task_group_s *group, size_t nbytes)
 {
-  DEBUGASSERT(group);
+  /* A NULL group pointer means the current group */
+
+  if (!group)
+    {
+      FAR struct tcb_s *tcb = (FAR struct tcb_s *)g_readytorun.head;
+      DEBUGASSERT(tcb && tcb->group);
+      group = tcb->group;
+    }
 
   /* Check the group type */