The patch titled
hvc_console: fix dropping of characters when output byte channel is full
has been added to the -mm tree. Its filename is
hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full.patch
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Subject: hvc_console: fix dropping of characters when output byte channel is full
From: Timur Tabi <timur@xxxxxxxxxxxxx>
hvc_console_print() calls the HVC client driver's put_chars() callback to
write some characters to the console. If the callback returns 0, that
indicates that no characters were written (perhaps the output buffer is
full), but hvc_console_print() treats that as an error and discards the
rest of the buffer.
So change hvc_console_print() to just loop and call put_chars() again if it
returns a 0 return code.
This change makes hvc_console_print() behave more like hvc_push(), which
does check for a 0 return code and re-schedules itself.
Signed-off-by: Timur Tabi <timur@xxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Amit Shah <amit.shah@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxx>
Cc: Kumar Gala <galak@xxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/char/hvc_console.c | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff -puN drivers/char/hvc_console.c~hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full drivers/char/hvc_console.c
--- a/drivers/char/hvc_console.c~hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full
+++ a/drivers/char/hvc_console.c
@@ -3,6 +3,7 @@
* Copyright (C) 2001 Paul Mackerras <paulus@xxxxxxxxxx>, IBM
* Copyright (C) 2004 Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, IBM Corp.
* Copyright (C) 2004 IBM Corporation
+ * Copyright 2009 Freescale Semiconductor, Inc.
*
* Additional Author(s):
* Ryan S. Arnold <rsa@xxxxxxxxxx>
@@ -141,6 +142,7 @@ static void hvc_console_print(struct con
char c[N_OUTBUF] __ALIGNED__;
unsigned i = 0, n = 0;
int r, donecr = 0, index = co->index;
+ unsigned int timeout = 1000000; /* Keep trying for up to one second */
/* Console access attempt outside of acceptable console range. */
if (index >= MAX_NR_HVC_CONSOLES)
@@ -152,6 +154,10 @@ static void hvc_console_print(struct con
while (count > 0 || i > 0) {
if (count > 0 && i < sizeof(c)) {
+ /* If the local buffer (c) is not full, then copy some
+ * bytes from the input buffer to it. We stop when the
+ * local buffer is full. \n is converted to \r\n.
+ */
if (b[n] == '\n' && !donecr) {
c[i++] = '\r';
donecr = 1;
@@ -162,14 +168,25 @@ static void hvc_console_print(struct con
}
} else {
r = cons_ops[index]->put_chars(vtermnos[index], c, i);
- if (r <= 0) {
+ if (r < 0) {
/* throw away chars on error */
i = 0;
} else if (r > 0) {
i -= r;
if (i > 0)
memmove(c, c+r, i);
+ } else {
+ /* If r == 0, then the client driver didn't do
+ * anything, so wait 1us and try again. If we
+ * time out, then just exit.
+ */
+ if (!--timeout)
+ return;
+ udelay(1);
+ continue;
}
+ /* Reset the timeout */
+ timeout = 1000000;
}
}
}
_
Patches currently in -mm which might be from timur@xxxxxxxxxxxxx are
linux-next.patch
hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full.patch
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