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Date: Wed, 15 Aug 2012 15:46:32 -0400 From: Paul Gortmaker <paul.gortmaker@...driver.com> To: <stable@...r.kernel.org>, <linux-kernel@...r.kernel.org> CC: Hendrik Brueckner <brueckner@...ux.vnet.ibm.com>, Benjamin Herrenschmidt <benh@...nel.crashing.org>, Paul Gortmaker <paul.gortmaker@...driver.com> Subject: [v2.6.34-stable 048/165] hvc_console: Improve tty/console put_chars handling From: Hendrik Brueckner <brueckner@...ux.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 <brueckner@...ux.vnet.ibm.com> Acked-by: Anton Blanchard <anton@...ba.org> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org> [PG: map drivers/tty/hvc/ --> drivers/char for v2.6.34 baseline] Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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