sched/semaphore: Move named semaphores to user space

fs/semaphore/sem_close.c

@@ -41,7 +41,7 @@
  ****************************************************************************/
 
 /****************************************************************************
- * Name:  sem_close
+ * Name:  nxsem_close
  *
  * Description:
  *   This function is called to indicate that the calling task is finished
@@ -57,7 +57,7 @@
  *  sem - semaphore descriptor
  *
  * Returned Value:
- *  0 (OK), or -1 (ERROR) if unsuccessful.
+ *  0 (OK), or negated errno if unsuccessful.
  *
  * Assumptions:
  *   - Care must be taken to avoid risking the deletion of a semaphore that
@@ -66,7 +66,7 @@
  *
  ****************************************************************************/
 
-int sem_close(FAR sem_t *sem)
+int nxsem_close(FAR sem_t *sem)
 {
   FAR struct nsem_inode_s *nsem;
   struct inode *inode;

fs/semaphore/sem_open.c

@@ -49,7 +49,7 @@
  ****************************************************************************/
 
 /****************************************************************************
- * Name: sem_open
+ * Name: nxsem_open
  *
  * Description:
  *   This function establishes a connection between named semaphores and a
@@ -81,43 +81,23 @@
  *        SEM_VALUE_MAX.
  *
  * Returned Value:
- *   A pointer to sem_t or SEM_FAILED if unsuccessful.
+ *   A pointer to sem_t or negated errno if unsuccessful.
  *
  * Assumptions:
  *
  ****************************************************************************/
 
-FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
+FAR sem_t *nxsem_open(FAR const char *name, int oflags, ...)
 {
   FAR struct inode *inode;
   FAR struct nsem_inode_s *nsem;
-  FAR sem_t *sem = (FAR sem_t *)ERROR;
+  FAR sem_t *sem;
   struct inode_search_s desc;
   char fullpath[MAX_SEMPATH];
   mode_t mode;
   unsigned value;
-  int errcode;
   int ret;
 
-  /* Make sure that a non-NULL name is supplied */
-
-  DEBUGASSERT(name != NULL);
-
-  if (name[0] == '/')
-    {
-      if (strlen(name) >= PATH_MAX)
-        {
-          set_errno(ENAMETOOLONG);
-          return SEM_FAILED;
-        }
-
-      if (strlen(strrchr(name, '/') + 1) >= NAME_MAX)
-        {
-          set_errno(ENAMETOOLONG);
-          return SEM_FAILED;
-        }
-    }
-
   /* Get the full path to the semaphore */
 
   snprintf(fullpath, MAX_SEMPATH,
@@ -141,7 +121,7 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
 
       if (!INODE_IS_NAMEDSEM(inode))
         {
-          errcode = ENXIO;
+          ret = -ENXIO;
           goto errout_with_inode;
         }
 
@@ -151,7 +131,7 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
 
       if ((oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
         {
-          errcode = EEXIST;
+          ret = -EEXIST;
           goto errout_with_inode;
         }
 
@@ -171,7 +151,7 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
         {
           /* The semaphore does not exist and O_CREAT is not set */
 
-          errcode = ENOENT;
+          ret = -ENOENT;
           goto errout_with_lock;
         }
 
@@ -189,7 +169,7 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
 
       if (value > SEM_VALUE_MAX)
         {
-          errcode = EINVAL;
+          ret = -EINVAL;
           goto errout_with_lock;
         }
 
@@ -200,7 +180,6 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
       ret = inode_lock();
       if (ret < 0)
         {
-          errcode = -ret;
           goto errout_with_lock;
         }
 
@@ -209,7 +188,6 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
 
       if (ret < 0)
         {
-          errcode = -ret;
           goto errout_with_lock;
         }
 
@@ -220,7 +198,7 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
       nsem = group_malloc(NULL, sizeof(struct nsem_inode_s));
       if (!nsem)
         {
-          errcode = ENOMEM;
+          ret = -ENOMEM;
           goto errout_with_inode;
         }
 
@@ -251,8 +229,7 @@ FAR sem_t *sem_open(FAR const char *name, int oflags, ...)
 
 errout_with_lock:
   RELEASE_SEARCH(&desc);
-  set_errno(errcode);
-  return SEM_FAILED;
+  return (FAR sem_t *)(intptr_t)ret;
 }
 
 #endif /* CONFIG_FS_NAMED_SEMAPHORES */

fs/semaphore/sem_unlink.c

@@ -41,7 +41,7 @@
  ****************************************************************************/
 
 /****************************************************************************
- * Name: sem_unlink
+ * Name: nxsem_unlink
  *
  * Description:
  *   This function removes the semaphore named by the input parameter 'name.'
@@ -55,18 +55,17 @@
  *   name - Semaphore name
  *
  * Returned Value:
- *  0 (OK), or -1 (ERROR) if unsuccessful.
+ *  0 (OK), or negated errno if unsuccessful.
  *
  * Assumptions:
  *
  ****************************************************************************/
 
-int sem_unlink(FAR const char *name)
+int nxsem_unlink(FAR const char *name)
 {
   FAR struct inode *inode;
   struct inode_search_s desc;
   char fullpath[MAX_SEMPATH];
-  int errcode;
   int ret;
 
   /* Get the full path to the semaphore */
@@ -83,7 +82,6 @@ int sem_unlink(FAR const char *name)
     {
       /* There is no inode that includes in this path */
 
-      errcode = -ret;
       goto errout_with_search;
     }
 
@@ -95,7 +93,7 @@ int sem_unlink(FAR const char *name)
 
   if (!INODE_IS_NAMEDSEM(inode))
     {
-      errcode = ENOENT;
+      ret = -ENOENT;
       goto errout_with_inode;
     }
 
@@ -106,13 +104,12 @@ int sem_unlink(FAR const char *name)
   ret = inode_lock();
   if (ret < 0)
     {
-      errcode = -ret;
       goto errout_with_inode;
     }
 
   if (inode->i_child != NULL)
     {
-      errcode = ENOTEMPTY;
+      ret = -ENOTEMPTY;
       goto errout_with_lock;
     }
 
@@ -139,7 +136,7 @@ int sem_unlink(FAR const char *name)
    */
 
   inode_unlock();
-  ret = sem_close(&inode->u.i_nsem->ns_sem);
+  ret = nxsem_close(&inode->u.i_nsem->ns_sem);
   RELEASE_SEARCH(&desc);
   return ret;
 
@@ -151,6 +148,5 @@ int sem_unlink(FAR const char *name)
 
 errout_with_search:
   RELEASE_SEARCH(&desc);
-  set_errno(errcode);
-  return ERROR;
+  return ret;
 }

include/nuttx/semaphore.h

@@ -384,6 +384,98 @@ int nxsem_post(FAR sem_t *sem);
 
 int nxsem_get_value(FAR sem_t *sem, FAR int *sval);
 
+/****************************************************************************
+ * Name: nxsem_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()).
+ *
+ * Input 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, 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.
+ *
+ * Returned Value:
+ *   A pointer to sem_t or negated errno if unsuccessful.
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+FAR sem_t *nxsem_open(FAR const char *name, int oflags, ...);
+
+/****************************************************************************
+ * Name:  nxsem_close
+ *
+ * Description:
+ *   This function is called to indicate that the calling task is finished
+ *   with the specified named semaphore, 'sem'.  The sem_close() deallocates
+ *   any system resources allocated by the system for this named semaphore.
+ *
+ *   If the semaphore has not been removed with a call to sem_unlink(), then
+ *   sem_close() has no effect on the named semaphore.  However, when the
+ *   named semaphore has been fully unlinked, the semaphore will vanish when
+ *   the last task closes it.
+ *
+ * Input Parameters:
+ *  sem - semaphore descriptor
+ *
+ * Returned Value:
+ *  0 (OK), or negated errno if unsuccessful.
+ *
+ * Assumptions:
+ *   - Care must be taken to avoid risking the deletion of a semaphore that
+ *     another calling task has already locked.
+ *   - sem_close must not be called for an un-named semaphore
+ *
+ ****************************************************************************/
+
+int nxsem_close(FAR sem_t *sem);
+
+/****************************************************************************
+ * Name: nxsem_unlink
+ *
+ * Description:
+ *   This function removes the semaphore named by the input parameter 'name.'
+ *   If the semaphore named by 'name' is currently referenced by other task,
+ *   the sem_unlink() will have no effect on the state of the semaphore.  If
+ *   one or more processes have the semaphore open when sem_unlink() is
+ *   called, destruction of the semaphore will be postponed until all
+ *   references to the semaphore have been destroyed by calls of sem_close().
+ *
+ * Input Parameters:
+ *   name - Semaphore name
+ *
+ * Returned Value:
+ *  0 (OK), or negated errno if unsuccessful.
+ *
+ * Assumptions:
+ *
+ ****************************************************************************/
+
+int nxsem_unlink(FAR const char *name);
+
 /****************************************************************************
  * Name: nxsem_reset
  *

include/sys/syscall_lookup.h

@@ -89,9 +89,9 @@ SYSCALL_LOOKUP(nxsem_wait,                 1)
 /* Named semaphores */
 
 #ifdef CONFIG_FS_NAMED_SEMAPHORES
-  SYSCALL_LOOKUP(sem_open,                 4)
-  SYSCALL_LOOKUP(sem_close,                1)
-  SYSCALL_LOOKUP(sem_unlink,               1)
+  SYSCALL_LOOKUP(nxsem_open,               4)
+  SYSCALL_LOOKUP(nxsem_close,              1)
+  SYSCALL_LOOKUP(nxsem_unlink,             1)
 #endif
 
 #ifndef CONFIG_BUILD_KERNEL

libs/libc/semaphore/CMakeLists.txt

@@ -30,4 +30,8 @@ set(SRCS
     sem_clockwait.c
     sem_post.c)
 
+if(CONFIG_FS_NAMED_SEMAPHORES)
+  list(APPEND SRCS sem_open.c sem_close.c sem_unlink.c)
+endif()
+
 target_sources(c PRIVATE ${SRCS})

libs/libc/semaphore/Make.defs

@@ -24,6 +24,10 @@ CSRCS += sem_init.c sem_setprotocol.c sem_getprotocol.c sem_getvalue.c
 CSRCS += sem_destroy.c sem_wait.c sem_trywait.c sem_timedwait.c
 CSRCS += sem_clockwait.c sem_post.c
 
+ifeq ($(CONFIG_FS_NAMED_SEMAPHORES),y)
+CSRCS += sem_open.c sem_close.c sem_unlink.c
+endif
+
 # Add the semaphore directory to the build
 
 DEPPATH += --dep-path semaphore