On Mon 2015-06-29 19:31:40, 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.
>
> Signed-off-by: Tejun Heo <t...@kernel.org>
> Reported-and-suggested-by: Geert Uytterhoeven <ge...@linux-m68k.org>
> ---
> Linus, Andrew.
>
> This removes an unnecessary 8k bss bloat introduced during v4.2-rc1
> merge window on certain configs. The original patch was routed
> through -mm. How should this be routed?
>
> Thanks.
>
> drivers/net/Kconfig | 1 +
> init/Kconfig | 3 +++
> kernel/printk/printk.c | 33 +++++++++++++++++++++++++++++----
> 3 files changed, 33 insertions(+), 4 deletions(-)
[...]
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
[...]
> @@ -2561,9 +2584,11 @@ void register_console(struct console *ne
> 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();
We should handle also the situation when CON_EXTENDED is set
and CONFIG_PRINTK_CON_EXTENDED is not set by mistake. Otherwise,
we will not increment nr_ext_console_drivers here => ext_text will
not be filled in console_unlock() => call_console_drivers()
will print nothing for the CON_EXTENDED console.
At least, I would print an error here. Something like.
#ifndef CONFIG_PRINTK_CON_EXTENDED
pr_err("The registered extended console will print nothing
because the kernel is not compiled with PRINTK_CON_EXTENDED\n");
#endif
I wonder if there is a good identification of the console that can be printed.
Otherwise, it looks fine to me.
Best Regards,
Petr
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