From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full.patch added to -mm tree Date: Tue, 14 Sep 2010 12:17:36 -0700 Message-ID: <201009141917.o8EJHaWW013296@imap1.linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:40443 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754727Ab0INTRw (ORCPT ); Tue, 14 Sep 2010 15:17:52 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org Cc: timur@freescale.com, amit.shah@redhat.com, benh@kernel.crashing.org, galak@gate.crashing.org, gregkh@suse.de The patch titled hvc_console: fix dropping of characters when output byte channel is full has been added to the -mm tree. Its filename is hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: hvc_console: fix dropping of characters when output byte channel is full From: Timur Tabi hvc_console_print() calls the HVC client driver's put_chars() callback to write some characters to the console. If the callback returns 0, that indicates that no characters were written (perhaps the output buffer is full), but hvc_console_print() treats that as an error and discards the rest of the buffer. So change hvc_console_print() to just loop and call put_chars() again if it returns a 0 return code. This change makes hvc_console_print() behave more like hvc_push(), which does check for a 0 return code and re-schedules itself. Signed-off-by: Timur Tabi Cc: Benjamin Herrenschmidt Cc: Amit Shah Cc: Greg Kroah-Hartman Cc: Kumar Gala Signed-off-by: Andrew Morton --- drivers/char/hvc_console.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff -puN drivers/char/hvc_console.c~hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full drivers/char/hvc_console.c --- a/drivers/char/hvc_console.c~hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full +++ a/drivers/char/hvc_console.c @@ -3,6 +3,7 @@ * Copyright (C) 2001 Paul Mackerras , IBM * Copyright (C) 2004 Benjamin Herrenschmidt , IBM Corp. * Copyright (C) 2004 IBM Corporation + * Copyright 2009 Freescale Semiconductor, Inc. * * Additional Author(s): * Ryan S. Arnold @@ -141,6 +142,7 @@ static void hvc_console_print(struct con char c[N_OUTBUF] __ALIGNED__; unsigned i = 0, n = 0; int r, donecr = 0, index = co->index; + unsigned int timeout = 1000000; /* Keep trying for up to one second */ /* Console access attempt outside of acceptable console range. */ if (index >= MAX_NR_HVC_CONSOLES) @@ -152,6 +154,10 @@ static void hvc_console_print(struct con while (count > 0 || i > 0) { if (count > 0 && i < sizeof(c)) { + /* If the local buffer (c) is not full, then copy some + * bytes from the input buffer to it. We stop when the + * local buffer is full. \n is converted to \r\n. + */ if (b[n] == '\n' && !donecr) { c[i++] = '\r'; donecr = 1; @@ -162,14 +168,25 @@ static void hvc_console_print(struct con } } else { r = cons_ops[index]->put_chars(vtermnos[index], c, i); - if (r <= 0) { + if (r < 0) { /* throw away chars on error */ i = 0; } else if (r > 0) { i -= r; if (i > 0) memmove(c, c+r, i); + } else { + /* If r == 0, then the client driver didn't do + * anything, so wait 1us and try again. If we + * time out, then just exit. + */ + if (!--timeout) + return; + udelay(1); + continue; } + /* Reset the timeout */ + timeout = 1000000; } } } _ Patches currently in -mm which might be from timur@freescale.com are linux-next.patch hvc_console-fix-dropping-of-characters-when-output-byte-channel-is-full.patch