libio: Add hold/drop iop reference

Check iop reference count in close() and return -1 with errno set to
EBUSY in case the file descriptor is still in use.

Update #3132.

1 files changed, 37 insertions, 4 deletions

diff --git a/cpukit/libcsupport/src/close.c b/cpukit/libcsupport/src/close.c
index 7eaeb64fea..d478e231c6 100644
--- a/cpukit/libcsupport/src/close.c
+++ b/cpukit/libcsupport/src/close.c
@@ -24,12 +24,45 @@ int close(
   int  fd
 )
 {
-  rtems_libio_t      *iop;
-  int                 rc;
+  rtems_libio_t *iop;
+  unsigned int   flags;
+  int            rc;
 
-  LIBIO_GET_IOP( fd, iop );
+  if ( (uint32_t) fd >= rtems_libio_number_iops ) {
+    rtems_set_errno_and_return_minus_one( EBADF );
+  }
 
-  rtems_libio_iop_flags_clear( iop, LIBIO_FLAGS_OPEN );
+  iop = rtems_libio_iop( fd );
+  flags = rtems_libio_iop_flags( iop );
+
+  while ( true ) {
+    unsigned int desired;
+    bool         success;
+
+    if ( ( flags & LIBIO_FLAGS_OPEN ) == 0 ) {
+      rtems_set_errno_and_return_minus_one( EBADF );
+    }
+
+    /* The expected flags */
+    flags &= LIBIO_FLAGS_REFERENCE_INC - 1U;
+
+    desired = flags & ~LIBIO_FLAGS_OPEN;
+    success = _Atomic_Compare_exchange_uint(
+      &iop->flags,
+      &flags,
+      desired,
+      ATOMIC_ORDER_ACQ_REL,
+      ATOMIC_ORDER_RELAXED
+    );
+
+    if ( success ) {
+      break;
+    }
+
+    if ( ( flags & ~( LIBIO_FLAGS_REFERENCE_INC - 1U ) ) != 0 ) {
+      rtems_set_errno_and_return_minus_one( EBUSY );
+    }
+  }
 
   rc = (*iop->pathinfo.handlers->close_h)( iop );