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, 3 insertions, 3 deletions

diff --git a/cpukit/libcsupport/src/sup_fs_deviceio.c b/cpukit/libcsupport/src/sup_fs_deviceio.c
index 294e14a260..4a7e0dd13c 100644
--- a/cpukit/libcsupport/src/sup_fs_deviceio.c
+++ b/cpukit/libcsupport/src/sup_fs_deviceio.c
@@ -34,7 +34,7 @@ int rtems_deviceio_open(
   rtems_libio_open_close_args_t args;
 
   args.iop = iop;
-  args.flags = iop->flags;
+  args.flags = rtems_libio_iop_flags( iop );
   args.mode = mode;
 
   status = rtems_io_open( major, minor, &args );
@@ -75,7 +75,7 @@ ssize_t rtems_deviceio_read(
   args.offset = iop->offset;
   args.buffer = buf;
   args.count = nbyte;
-  args.flags = iop->flags;
+  args.flags = rtems_libio_iop_flags( iop );
   args.bytes_moved = 0;
 
   status = rtems_io_read( major, minor, &args );
@@ -103,7 +103,7 @@ ssize_t rtems_deviceio_write(
   args.offset = iop->offset;
   args.buffer = RTEMS_DECONST( void *, buf );
   args.count = nbyte;
-  args.flags = iop->flags;
+  args.flags = rtems_libio_iop_flags( iop );
   args.bytes_moved = 0;
 
   status = rtems_io_write( major, minor, &args );