Messages in this thread | | | Date | Wed, 1 Jul 2015 18:05:13 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH v4.2-rc1] printk: make extended printk support conditional on netconsole |
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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 <tj@kernel.org> > Reported-and-suggested-by: Geert Uytterhoeven <geert@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(-)
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> --- 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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