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From: Nathan Lynch <nathanl@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: mpe@ellerman.id.au, linux-kernel@vger.kernel.org,
	gregkh@linuxfoundation.org, jirislaby@kernel.org
Subject: [PATCH] powerpc/udbg_hvc: retry putc on -EAGAIN
Date: Fri, 14 May 2021 16:44:22 -0500	[thread overview]
Message-ID: <20210514214422.3019105-1-nathanl@linux.ibm.com> (raw)

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 <nathanl@linux.ibm.com>
---
 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


WARNING: multiple messages have this Message-ID (diff)
From: Nathan Lynch <nathanl@linux.ibm.com>
To: linuxppc-dev@lists.ozlabs.org
Cc: jirislaby@kernel.org, linux-kernel@vger.kernel.org,
	gregkh@linuxfoundation.org
Subject: [PATCH] powerpc/udbg_hvc: retry putc on -EAGAIN
Date: Fri, 14 May 2021 16:44:22 -0500	[thread overview]
Message-ID: <20210514214422.3019105-1-nathanl@linux.ibm.com> (raw)

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 <nathanl@linux.ibm.com>
---
 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


             reply	other threads:[~2021-05-14 21:44 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-14 21:44 Nathan Lynch [this message]
2021-05-14 21:44 ` [PATCH] powerpc/udbg_hvc: retry putc on -EAGAIN Nathan Lynch
2021-05-21 12:47 ` Greg KH
2021-05-21 12:47   ` Greg KH
2021-05-23 10:51   ` Michael Ellerman
2021-05-23 10:51     ` Michael Ellerman
2021-05-27 11:10     ` Greg KH
2021-05-27 11:10       ` Greg KH
2021-06-06 12:08 ` Michael Ellerman

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