From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932101Ab1G1XzK (ORCPT ); Thu, 28 Jul 2011 19:55:10 -0400 Received: from mga01.intel.com ([192.55.52.88]:7365 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756113Ab1G1XoU (ORCPT ); Thu, 28 Jul 2011 19:44:20 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.67,285,1309762800"; d="scan'208";a="33559435" From: Andi Kleen References: <20110728444.299940435@firstfloor.org> In-Reply-To: <20110728444.299940435@firstfloor.org> To: brueckner@linux.vnet.ibm.com, anton@samba.org, benh@kernel.crashing.org, ak@linux.intel.com, linux-kernel@vger.kernel.org, stable@kernel.org, tim.bird@am.sony.com Subject: [PATCH] [15/50] hvc_console: Improve tty/console put_chars handling Message-Id: <20110728234419.8FD482403FF@tassilo.jf.intel.com> Date: Thu, 28 Jul 2011 16:44:19 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.35-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Hendrik Brueckner [ upstream commit 8c2381af0d3ef62a681dac5a141b6dabb27bf2e1 ] 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 Cc: Signed-off-by: Benjamin Herrenschmidt Signed-off-by: Andi Kleen Index: linux-2.6.35.y/drivers/char/hvc_console.c =================================================================== --- linux-2.6.35.y.orig/drivers/char/hvc_console.c +++ linux-2.6.35.y/drivers/char/hvc_console.c @@ -163,8 +163,10 @@ 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) @@ -448,7 +450,7 @@ 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; }