From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-Id: <20111102221453.222863192@clark.kroah.org> Date: Wed, 02 Nov 2011 15:14:00 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Hendrik Brueckner , Anton Blanchard , Benjamin Herrenschmidt Subject: [034/107] hvc_console: Improve tty/console put_chars handling In-Reply-To: <20111102221600.GA26650@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: 2.6.32-longterm review patch. If anyone has any objections, please let us know. ------------------ From: Hendrik Brueckner 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 Acked-by: Anton Blanchard Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Greg Kroah-Hartman --- drivers/char/hvc_console.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/drivers/char/hvc_console.c +++ b/drivers/char/hvc_console.c @@ -162,8 +162,10 @@ static void hvc_console_print(struct con } 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) @@ -447,7 +449,7 @@ static int hvc_push(struct hvc_struct *h 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; }