From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH v2 v4.2-rc1] printk: make extended printk support conditional on netconsole Date: Thu, 2 Jul 2015 12:21:41 -0400 Message-ID: <20150702162141.GC30677@mtj.duckdns.org> References: <1430318704-32374-1-git-send-email-tj@kernel.org> <1430318704-32374-4-git-send-email-tj@kernel.org> <20150629152805.GM15805@mtj.duckdns.org> <20150629154914.GQ15805@mtj.duckdns.org> <20150629161355.GS15805@mtj.duckdns.org> <20150629233140.GA7711@mtj.duckdns.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: pmladek@suse.cz, "David S. Miller" , "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , Kay Sievers , Josh Triplett , Linux Embedded , Geert Uytterhoeven To: Linus Torvalds , Andrew Morton Return-path: Received: from mail-yk0-f172.google.com ([209.85.160.172]:34496 "EHLO mail-yk0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753660AbbGBQVp (ORCPT ); Thu, 2 Jul 2015 12:21:45 -0400 Content-Disposition: inline In-Reply-To: <20150629233140.GA7711@mtj.duckdns.org> Sender: netdev-owner@vger.kernel.org List-ID: 6fe29354befe ("printk: implement support for extended console drivers") implemented extended printk support for extended netconsole. The code added was miniscule but it added static 8k buffer unconditionally unnecessarily bloating the kernel for cases where extended netconsole is not used. This patch introduces CONFIG_PRINTK_CON_EXTENDED which is selected by CONFIG_NETCONSOLE. If the config option is not set, extended printk support is compiled out along with the static buffer. Verified 8k reduction in vmlinux bss when !CONFIG_NETCONSOLE. v2: Added a warning for cases where CON_EXTENDED is requested while CONFIG_PRINTK_CON_EXTENDED is disabled as suggested by Petr. Cc: Petr Mladek Signed-off-by: Tejun Heo Reported-and-suggested-by: Geert Uytterhoeven --- drivers/net/Kconfig | 1 + init/Kconfig | 3 +++ kernel/printk/printk.c | 40 ++++++++++++++++++++++++++++++++++++---- 3 files changed, 40 insertions(+), 4 deletions(-) diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig index 019fcef..39587f1 100644 --- a/drivers/net/Kconfig +++ b/drivers/net/Kconfig @@ -195,6 +195,7 @@ config GENEVE config NETCONSOLE tristate "Network console logging support" + select PRINTK_CON_EXTENDED ---help--- If you want to log kernel messages over the network, enable this. See for details. diff --git a/init/Kconfig b/init/Kconfig index bcc41bd..cd281ab 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1438,6 +1438,9 @@ config PRINTK very difficult to diagnose system problems, saying N here is strongly discouraged. +config PRINTK_CON_EXTENDED + bool + config BUG bool "BUG() support" if EXPERT default y diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index cf8c242..f719118 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -84,6 +84,10 @@ static struct lockdep_map console_lock_dep_map = { }; #endif +#ifdef CONFIG_PRINTK_CON_EXTENDED + +#define CONSOLE_EXT_LOG_BUF_LEN CONSOLE_EXT_LOG_MAX + /* * Number of registered extended console drivers. * @@ -96,6 +100,32 @@ static struct lockdep_map console_lock_dep_map = { */ static int nr_ext_console_drivers; +static void inc_nr_ext_console_drivers(void) +{ + nr_ext_console_drivers++; +} + +static void dec_nr_ext_console_drivers(void) +{ + nr_ext_console_drivers--; +} + +#else /* CONFIG_PRINTK_CON_EXTENDED */ + +#define CONSOLE_EXT_LOG_BUF_LEN 0 +#define nr_ext_console_drivers 0 + +static void inc_nr_ext_console_drivers(void) +{ + WARN_ONCE(true, "printk: CON_EXTENDED requested when !CONFIG_PRINTK_CON_EXTENDED\n"); +} + +static void dec_nr_ext_console_drivers(void) +{ +} + +#endif /* CONFIG_PRINTK_CON_EXTENDED */ + /* * Helper macros to handle lockdep when locking/unlocking console_sem. We use * macros instead of functions so that _RET_IP_ contains useful information. @@ -2224,7 +2254,7 @@ static void console_cont_flush(char *text, size_t size) */ void console_unlock(void) { - static char ext_text[CONSOLE_EXT_LOG_MAX]; + static char ext_text[CONSOLE_EXT_LOG_BUF_LEN]; static char text[LOG_LINE_MAX + PREFIX_MAX]; static u64 seen_seq; unsigned long flags; @@ -2561,9 +2591,11 @@ void register_console(struct console *newcon) console_drivers->next = newcon; } - if (newcon->flags & CON_EXTENDED) - if (!nr_ext_console_drivers++) + if (newcon->flags & CON_EXTENDED) { + if (!nr_ext_console_drivers) pr_info("printk: continuation disabled due to ext consoles, expect more fragments in /dev/kmsg\n"); + inc_nr_ext_console_drivers(); + } if (newcon->flags & CON_PRINTBUFFER) { /* @@ -2638,7 +2670,7 @@ int unregister_console(struct console *console) } if (!res && (console->flags & CON_EXTENDED)) - nr_ext_console_drivers--; + dec_nr_ext_console_drivers(); /* * If this isn't the last console and it has CON_CONSDEV set, we