libio: Robust file descriptor reference counting

There was a race conditon in the reference counting of file descriptors
during a close() operation.  After the call to the close handler, the
rtems_libio_free() function cleared the flags to zero.  However, at this
point in time there may still exist some holders of the file descriptor.
With RTEMS_DEBUG enabled this could lead to failed assertions in
rtems_libio_iop_drop().

Change the code to use only atomic read-modify-write operations on the
rtems_libio_iop::flags.

1 files changed, 1 insertions, 23 deletions

diff --git a/cpukit/include/rtems/libio_.h b/cpukit/include/rtems/libio_.h
index 916ba85b31..e9eb46263e 100644
--- a/cpukit/include/rtems/libio_.h
+++ b/cpukit/include/rtems/libio_.h
@@ -85,28 +85,6 @@ extern rtems_filesystem_mount_table_entry_t rtems_filesystem_null_mt_entry;
 extern rtems_filesystem_global_location_t rtems_filesystem_global_location_null;
 
 /**
- * @brief Sets the iop flags to the specified flags together with
- * LIBIO_FLAGS_OPEN.
- *
- * Use this once a file descriptor allocated via rtems_libio_allocate() is
- * fully initialized.
- *
- * @param[in] iop The iop.
- * @param[in] flags The flags.
- */
-static inline void rtems_libio_iop_flags_initialize(
-  rtems_libio_t *iop,
-  uint32_t       flags
-)
-{
-  _Atomic_Store_uint(
-    &iop->flags,
-    LIBIO_FLAGS_OPEN | flags,
-    ATOMIC_ORDER_RELEASE
-  );
-}
-
-/**
  * @brief Sets the specified flags in the iop.
  *
  * @param[in] iop The iop.
@@ -222,7 +200,7 @@ static inline void rtems_libio_iop_drop( rtems_libio_t *iop )
 
 #define rtems_libio_check_is_open(_iop) \
   do {                                               \
-      if (((_iop)->flags & LIBIO_FLAGS_OPEN) == 0) { \
+      if ((rtems_libio_iop_flags(_iop) & LIBIO_FLAGS_OPEN) == 0) { \
           errno = EBADF;                             \
           return -1;                                 \
       }                                              \