# \[PATCH\] powerpc/udbg\_hvc: retry putc on -EAGAIN

- From: Nathan Lynch \<hidden\>
- Date: 2021-05-14 21:44:37 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2021/05/1378232
- Thread: https://ratatoskr.run/linuxppc-dev/2021/05/1378232/t.md

```text
hvterm_raw_put_chars() calls hvc_put_chars(), which may return -EAGAIN
when the underlying hcall returns a "busy" status, but udbg_hvc_putc()
doesn't handle this. When using xmon on a PowerVM guest, this can
result in incomplete or garbled output when printing relatively large
amounts of data quickly, such as when dumping the kernel log buffer.

Call again on -EAGAIN.

Signed-off-by: Nathan Lynch <redacted>
---
 drivers/tty/hvc/hvc_vio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/hvc/hvc_vio.c b/drivers/tty/hvc/hvc_vio.c
index 798f27f40cc2..76d2a7038095 100644
--- a/drivers/tty/hvc/hvc_vio.c
+++ b/drivers/tty/hvc/hvc_vio.c
@@ -249,7 +249,7 @@ static void udbg_hvc_putc(char c)
 			count = hvterm_hvsi_put_chars(0, &c, 1);
 			break;
 		}
-	} while(count == 0);
+	} while(count == 0 || count == -EAGAIN);
 }
 
 static int udbg_hvc_getc_poll(void)
-- 
2.30.2

```