Fix wait loop and void cast (#24)

* Simplify EINTR/ECANCEL error handling

1. Add semaphore uninterruptible wait function
2 .Replace semaphore wait loop with a single uninterruptible wait
3. Replace all sem_xxx to nxsem_xxx

* Unify the void cast usage

1. Remove void cast for function because many place ignore the returned value witout cast
2. Replace void cast for variable with UNUSED macro

fs/vfs/fs_close.c

@@ -86,7 +86,7 @@ int close(int fd)
 
   /* close() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Did we get a valid file descriptor? */
 

fs/vfs/fs_fcntl.c

@@ -285,7 +285,7 @@ int fcntl(int fd, int cmd, ...)
 
   /* fcntl() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Setup to access the variable argument list */
 

fs/vfs/fs_fdopen.c

@@ -222,7 +222,7 @@ FAR struct file_struct *fs_fdopen(int fd, int oflags, FAR struct tcb_s *tcb)
 #ifndef CONFIG_STDIO_DISABLE_BUFFERING
           /* Initialize the semaphore the manages access to the buffer */
 
-          (void)nxsem_init(&stream->fs_sem, 0, 1);
+          nxsem_init(&stream->fs_sem, 0, 1);
 
 #if CONFIG_STDIO_BUFFER_SIZE > 0
           /* Allocate the IO buffer at the appropriate privilege level for

fs/vfs/fs_fsync.c

@@ -110,7 +110,7 @@ int fsync(int fd)
 
   /* fsync() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Get the file structure corresponding to the file descriptor. */
 

fs/vfs/fs_open.c

@@ -339,7 +339,7 @@ int open(FAR const char *path, int oflags, ...)
 
   /* open() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Let nx_vopen() do most of the work */
 

fs/vfs/fs_poll.c

@@ -72,18 +72,7 @@
 
 static int poll_semtake(FAR sem_t *sem)
 {
-  int ret;
-
-  /* Take the semaphore (perhaps waiting) */
-
-  ret = nxsem_wait(sem);
-
-  /* The only case that an error should occur here is if the wait were
-   * awakened by a signal.
-   */
-
-  DEBUGASSERT(ret == OK || ret == -EINTR);
-  return ret;
+  return nxsem_wait(sem);
 }
 
 /****************************************************************************
@@ -204,16 +193,16 @@ static inline int poll_setup(FAR struct pollfd *fds, nfds_t nfds,
               switch (fds[j].events & POLLMASK)
                 {
                 case POLLFD:
-                  (void)poll_fdsetup(fds[j].fd, &fds[j], false);
+                  poll_fdsetup(fds[j].fd, &fds[j], false);
                   break;
 
                 case POLLFILE:
-                  (void)file_poll(fds[j].ptr, &fds[j], false);
+                  file_poll(fds[j].ptr, &fds[j], false);
                   break;
 
 #ifdef CONFIG_NET
                 case POLLSOCK:
-                  (void)psock_poll(fds[j].ptr, &fds[j], false);
+                  psock_poll(fds[j].ptr, &fds[j], false);
                   break;
 #endif
 
@@ -452,7 +441,7 @@ int poll(FAR struct pollfd *fds, nfds_t nfds, int timeout)
 
   /* poll() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* This semaphore is used for signaling and, hence, should not have
    * priority inheritance enabled.

fs/vfs/fs_pread.c

@@ -143,7 +143,7 @@ ssize_t pread(int fd, FAR void *buf, size_t nbytes, off_t offset)
 
   /* pread() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Get the file structure corresponding to the file descriptor. */
 

fs/vfs/fs_pwrite.c

@@ -146,7 +146,7 @@ ssize_t pwrite(int fd, FAR const void *buf, size_t nbytes, off_t offset)
 
   /* pread() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Get the file structure corresponding to the file descriptor. */
 

fs/vfs/fs_read.c

@@ -199,7 +199,7 @@ ssize_t read(int fd, FAR void *buf, size_t nbytes)
 
   /* read() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Let nx_read() do the real work */
 

fs/vfs/fs_readlink.c

@@ -122,7 +122,7 @@ ssize_t readlink(FAR const char *path, FAR char *buf, size_t bufsize)
   /* Copy the link target pathto the user-provided buffer. */
 
   *buf = '\0';
-  (void)strncpy(buf, node->u.i_link, bufsize);
+  strncpy(buf, node->u.i_link, bufsize);
 
   /* Release our reference on the inode and return the length */
 

fs/vfs/fs_rename.c

@@ -115,7 +115,7 @@ static int pseudorename(FAR const char *oldpath, FAR struct inode *oldinode,
 
       subdirname = basename((FAR char *)oldpath);
 
-      (void)asprintf(&subdir, "/%s", subdirname);
+      asprintf(&subdir, "/%s", subdirname);
       if (subdir == NULL)
         {
           ret = -ENOMEM;
@@ -179,7 +179,7 @@ next_subdir:
           tmp        = subdir;
           subdir     = NULL;
 
-          (void)asprintf(&subdir, "%s/%s", newpath, subdirname);
+          asprintf(&subdir, "%s/%s", newpath, subdirname);
 
           if (tmp != NULL)
             {
@@ -213,7 +213,7 @@ next_subdir:
            * won't really be removed until we call inode_release();
            */
 
-          (void)inode_remove(newpath);
+          inode_remove(newpath);
         }
 
       inode_release(newinode);
@@ -274,7 +274,7 @@ next_subdir:
     {
       /* Remove the new node we just recreated */
 
-      (void)inode_remove(newpath);
+      inode_remove(newpath);
       goto errout_with_sem;
     }
 
@@ -415,8 +415,8 @@ next_subdir:
                       FAR char *tmp = subdir;
 
                       subdir = NULL;
-                      (void)asprintf(&subdir, "%s/%s", newrelpath,
-                                     subdirname);
+                      asprintf(&subdir, "%s/%s", newrelpath,
+                               subdirname);
 
                       if (tmp != NULL)
                         {
@@ -450,7 +450,7 @@ next_subdir:
                    * should check that.
                    */
 
-                   (void)oldinode->u.i_mops->unlink(oldinode, newrelpath);
+                   oldinode->u.i_mops->unlink(oldinode, newrelpath);
                 }
             }
         }

fs/vfs/fs_select.c

@@ -103,7 +103,7 @@ int select(int nfds, FAR fd_set *readfds, FAR fd_set *writefds,
 
   /* select() is cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* How many pollfd structures do we need to allocate? */
 

fs/vfs/fs_write.c

@@ -232,7 +232,7 @@ ssize_t write(int fd, FAR const void *buf, size_t nbytes)
 
   /* write() is a cancellation point */
 
-  (void)enter_cancellation_point();
+  enter_cancellation_point();
 
   /* Let nx_write() do all of the work */