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Date: Fri, 3 Jul 2015 16:07:34 +0200 From: Petr Mladek <pmladek@...e.com> To: Tejun Heo <tj@...nel.org> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, "David S. Miller" <davem@...emloft.net>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, Kay Sievers <kay@...y.org>, Josh Triplett <josh@...htriplett.org>, Linux Embedded <linux-embedded@...r.kernel.org>, geert@...ux-m68k.org Subject: Re: [PATCH v2 v4.2-rc1] printk: make extended printk support conditional on netconsole On Thu 2015-07-02 12:21:41, Tejun Heo wrote: > 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 <pmladek@...e.com> > Signed-off-by: Tejun Heo <tj@...nel.org> > Reported-and-suggested-by: Geert Uytterhoeven <geert@...ux-m68k.org> Reviewed-by: Petr Mladek <pmladek@...e.cz> There is still one small thing that might get improved, see below. But it is not that important and might be solved later. I am sorry for not noticing it last time. > 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. > @@ -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"); I would move the check and the message into inc_nr_ext_console_drivers() when CONFIG_PRINTK_CON_EXTENDED is defined. It does not make sense if we do not increment the counter. Best Regards, Petr -- 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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