Filesystem: Remove per file descriptor semaphore

The per file descriptor semaphore (field of rtems_libio_t) is unused in
RTEMS.  There is a considerable memory overhead due to that.  A
semaphore needs roughly 124 bytes which is huge compared to the
approximately 72 bytes for the file descriptor structure itself.  Device
drivers can create their own synchronization primitives in the open
handler on demand.

3 files changed, 6 insertions, 29 deletions

diff --git a/cpukit/libcsupport/include/rtems/libio.h b/cpukit/libcsupport/include/rtems/libio.h
index f1908f7da2..04ca52c4aa 100644
--- a/cpukit/libcsupport/include/rtems/libio.h
+++ b/cpukit/libcsupport/include/rtems/libio.h
@@ -1165,7 +1165,6 @@ struct rtems_libio_tt {
   off_t                                   offset;    /* current offset into file */
   uint32_t                                flags;
   rtems_filesystem_location_info_t        pathinfo;
-  rtems_id                                sem;
   uint32_t                                data0;     /* private to "driver" */
   void                                   *data1;     /* ... */
 };
diff --git a/cpukit/libcsupport/src/libio.c b/cpukit/libcsupport/src/libio.c
index 985ad8bad9..e75b66bfaf 100644
--- a/cpukit/libcsupport/src/libio.c
+++ b/cpukit/libcsupport/src/libio.c
@@ -131,36 +131,19 @@ int rtems_libio_to_fcntl_flags( uint32_t flags )
 
 rtems_libio_t *rtems_libio_allocate( void )
 {
-  rtems_libio_t *iop, *next;
-  rtems_status_code rc;
-  rtems_id sema;
+  rtems_libio_t *iop = NULL;
 
   rtems_libio_lock();
 
   if (rtems_libio_iop_freelist) {
-    rc = rtems_semaphore_create(
-      RTEMS_LIBIO_IOP_SEM(rtems_libio_iop_freelist - rtems_libio_iops),
-      1,
-      RTEMS_BINARY_SEMAPHORE | RTEMS_INHERIT_PRIORITY | RTEMS_PRIORITY,
-      0,
-      &sema
-    );
-    if (rc != RTEMS_SUCCESSFUL)
-      goto failed;
     iop = rtems_libio_iop_freelist;
-    next = iop->data1;
-    (void) memset( iop, 0, sizeof(rtems_libio_t) );
+    rtems_libio_iop_freelist = iop->data1;
+    memset( iop, 0, sizeof(*iop) );
     iop->flags = LIBIO_FLAGS_OPEN;
-    iop->sem = sema;
-    rtems_libio_iop_freelist = next;
-    goto done;
   }
 
-failed:
-  iop = 0;
-
-done:
   rtems_libio_unlock();
+
   return iop;
 }
 
@@ -179,9 +162,6 @@ void rtems_libio_free(
 
   rtems_libio_lock();
 
-    if (iop->sem)
-      rtems_semaphore_delete(iop->sem);
-
     iop->flags &= ~LIBIO_FLAGS_OPEN;
     iop->data1 = rtems_libio_iop_freelist;
     rtems_libio_iop_freelist = iop;
diff --git a/cpukit/sapi/include/confdefs.h b/cpukit/sapi/include/confdefs.h
index d896c59e82..3e4cb90940 100644
--- a/cpukit/sapi/include/confdefs.h
+++ b/cpukit/sapi/include/confdefs.h
@@ -119,11 +119,9 @@ rtems_fs_init_functions_t    rtems_fs_init_helper =
 #endif
 
 /**
- *  From the number of file descriptors, we can determine how many
- *  semaphores the implementation will require.
+ *  Semaphore count used by the IO library.
  */
-#define CONFIGURE_LIBIO_SEMAPHORES \
-  (CONFIGURE_LIBIO_MAXIMUM_FILE_DESCRIPTORS + 1)
+#define CONFIGURE_LIBIO_SEMAPHORES 1
 
 #ifdef CONFIGURE_INIT
   /**