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authorHendrik Brueckner <brueckner@linux.vnet.ibm.com>2011-07-05 21:50:18 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2011-07-19 15:13:05 +1000
commit8c2381af0d3ef62a681dac5a141b6dabb27bf2e1 (patch)
tree42cd8aaecca37a7fce9d81d20fcd78f9d86647b1 /drivers/tty/hvc/hvc_console.c
parentpowerpc/kdump: Fix timeout in crash_kexec_wait_realmode (diff)
downloadlinux-dev-8c2381af0d3ef62a681dac5a141b6dabb27bf2e1.tar.xz
linux-dev-8c2381af0d3ef62a681dac5a141b6dabb27bf2e1.zip
hvc_console: Improve tty/console put_chars handling
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 <brueckner@linux.vnet.ibm.com> Acked-by: Anton Blanchard <anton@samba.org> Cc: <stable@kernel.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'drivers/tty/hvc/hvc_console.c')
-rw-r--r--drivers/tty/hvc/hvc_console.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
index f8ff6f50fc35..59000750cc73 100644
--- a/drivers/tty/hvc/hvc_console.c
+++ b/drivers/tty/hvc/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;
}