From: Hendrik Brueckner <brueck...@linux.vnet.ibm.com>
-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
If you see a problem with using this for longterm, please comment.
-------------------
commit 8c2381af0d3ef62a681dac5a141b6dabb27bf2e1 upstream.
Currently, the hvc_console_print() function drops console output if the
hvc backend's put_chars() returns 0. This patch changes this behavior
to allow a retry through returning -EAGAIN.
This change also affects the hvc_push() function. Both functions are
changed to handle -EAGAIN and to retry the put_chars() operation.
If a hvc backend returns -EAGAIN, the retry handling differs:
- hvc_console_print() spins to write the complete console output.
- hvc_push() behaves the same way as for returning 0.
Now hvc backends can indirectly control the way how console output is
handled through the hvc console layer.
Signed-off-by: Hendrik Brueckner <brueck...@linux.vnet.ibm.com>
Acked-by: Anton Blanchard <an...@samba.org>
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
[PG: map drivers/tty/hvc/ --> drivers/char for v2.6.34 baseline]
Signed-off-by: Paul Gortmaker <paul.gortma...@windriver.com>
---
drivers/char/hvc_console.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index 35cca4c..8417efe 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -163,8 +163,10 @@ static void hvc_console_print(struct console *co, const
char *b,
} else {
r = cons_ops[index]->put_chars(vtermnos[index], c, i);
if (r <= 0) {
- /* throw away chars on error */
- i = 0;
+ /* throw away characters on error
+ * but spin in case of -EAGAIN */
+ if (r != -EAGAIN)
+ i = 0;
} else if (r > 0) {
i -= r;
if (i > 0)
@@ -448,7 +450,7 @@ static int hvc_push(struct hvc_struct *hp)
n = hp->ops->put_chars(hp->vtermno, hp->outbuf, hp->n_outbuf);
if (n <= 0) {
- if (n == 0) {
+ if (n == 0 || n == -EAGAIN) {
hp->do_wakeup = 1;
return 0;
}
--
1.7.12.rc2
--
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