kgdb: Respect that flush op is optional

Not all kgdb I/O drivers implement a flush operation. Adjust
gdbstub_exit accordingly.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c
index c22d8c28ad84..5a155742ae96 100644
--- a/kernel/debug/gdbstub.c
+++ b/kernel/debug/gdbstub.c
@@ -1129,5 +1129,6 @@ void gdbstub_exit(int status)
         dbg_io_ops->write_char(hex_asc_lo(checksum));
 
         /* make sure the output is flushed, lest the bootloader clobber it */
-        dbg_io_ops->flush();
+        if (dbg_io_ops->flush)
+                dbg_io_ops->flush();
 }