linux-kernel - Re: [PATCH] earlyprintk: re-enable earlyprintk calling early

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Message-ID: <20140827151504.GA22824@ulmo>
Date:	Wed, 27 Aug 2014 17:15:10 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	kpark3469@...il.com
Cc:	akpm@...ux-foundation.org, keun-o.park@...driver.com,
	hpa@...or.com, rafael.j.wysocki@...el.com, peterz@...radead.org,
	rusty@...tcorp.com.au, kirill.shutemov@...ux.intel.com,
	oleg@...hat.com, prarit@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] earlyprintk: re-enable earlyprintk calling early_param

On Thu, Aug 14, 2014 at 07:13:36PM +0900, kpark3469@...il.com wrote:
> From: Sahara <keun-o.park@...driver.com>
> 
> Although there are many obs_kernel_param and its names are
> earlyprintk and also EARLY_PRINTK is also enabled, we could not
> see the early_printk output properly until now. This patch
> considers earlycon as well as earlyprintk.
> 
> Signed-off-by: Sahara <keun-o.park@...driver.com>
> ---
>  init/main.c |    3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/init/main.c b/init/main.c
> index bb1aed9..235d248 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -426,7 +426,8 @@ static int __init do_early_param(char *param, char *val, const char *unused)
>  	for (p = __setup_start; p < __setup_end; p++) {
>  		if ((p->early && parameq(param, p->str)) ||
>  		    (strcmp(param, "console") == 0 &&
> -		     strcmp(p->str, "earlycon") == 0)
> +		     ((strcmp(p->str, "earlycon") == 0) ||
> +		     (strcmp(p->str, "earlyprintk") == 0)))
>  		) {
>  			if (p->setup_func(val) != 0)
>  				pr_warn("Malformed early option '%s'\n", param);

It seems like this patch causes the following warning for me during
boot:

[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Initializing cgroup subsys cpu
[    0.000000] Initializing cgroup subsys cpuacct
[    0.000000] Linux version 3.17.0-rc2-next-20140827 (thierry.reding@...o) (gcc version 4.9.0 (GCC) ) #18 SMP PREEMPT Wed Aug 27 17:08:12 CEST 2014
[    0.000000] CPU: ARMv7 Processor [413fc0f3] revision 3 (ARMv7), cr=10c5387d
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, PIPT instruction cache
[    0.000000] Machine model: NVIDIA Tegra124 Jetson TK1
[    0.000000] bootconsole [earlycon0] enabled
[    0.000000] debug: ignoring loglevel setting.
[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: CPU: 0 PID: 0 at /home/thierry.reding/src/kernel/linux-work.git/kernel/printk/printk.c:2402 register_console+0x60/0x37c()
[    0.000000] console 'earlycon0' already registered
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 3.17.0-rc2-next-20140827 #18
[    0.000000] [<c0015fec>] (unwind_backtrace) from [<c0011aac>] (show_stack+0x10/0x14)
[    0.000000] [<c0011aac>] (show_stack) from [<c062b700>] (dump_stack+0x98/0xd8)
[    0.000000] [<c062b700>] (dump_stack) from [<c0025ba0>] (warn_slowpath_common+0x70/0x8c)
[    0.000000] [<c0025ba0>] (warn_slowpath_common) from [<c0025bec>] (warn_slowpath_fmt+0x30/0x40)
[    0.000000] [<c0025bec>] (warn_slowpath_fmt) from [<c00639b8>] (register_console+0x60/0x37c)
[    0.000000] [<c00639b8>] (register_console) from [<c0883870>] (setup_early_printk+0x20/0x28)
[    0.000000] [<c0883870>] (setup_early_printk) from [<c087f43c>] (do_early_param+0x6c/0xd0)
[    0.000000] [<c087f43c>] (do_early_param) from [<c003cba0>] (parse_args+0x238/0x3d0)
[    0.000000] [<c003cba0>] (parse_args) from [<c087f814>] (parse_early_options+0x38/0x40)
[    0.000000] [<c087f814>] (parse_early_options) from [<c087f84c>] (parse_early_param+0x30/0x40)
[    0.000000] [<c087f84c>] (parse_early_param) from [<c088206c>] (setup_arch+0x4b4/0x974)
[    0.000000] [<c088206c>] (setup_arch) from [<c087f8f8>] (start_kernel+0x98/0x3a8)
[    0.000000] [<c087f8f8>] (start_kernel) from [<80008074>] (0x80008074)
[    0.000000] ---[ end trace cb88537fdc8fa200 ]---
[    0.000000] cma: Reserved 128 MiB at a7800000
[    0.000000] Memory policy: Data cache writealloc
[    0.000000] On node 0 totalpages: 524032
[    0.000000] free_area_init_node: node 0, pgdat c091cc00, node_mem_map e67b7000
[    0.000000]   Normal zone: 1520 pages used for memmap
[    0.000000]   Normal zone: 0 pages reserved
[    0.000000]   Normal zone: 194560 pages, LIFO batch:31
[    0.000000]   HighMem zone: 2574 pages used for memmap
[    0.000000]   HighMem zone: 329472 pages, LIFO batch:31
[    0.000000] PERCPU: Embedded 8 pages/cpu @e6767000 s8832 r8192 d15744 u32768
[    0.000000] pcpu-alloc: s8832 r8192 d15744 u32768 alloc=8*4096
[    0.000000] pcpu-alloc: [0] 0 [0] 1 [0] 2 [0] 3
[    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 522512
[    0.000000] Kernel command line: console=ttyS0,115200n8 ignore_loglevel rootwait ro earlyprintk ip=:::::eth0:dhcp root=/dev/nfs nfsroot=192.168.69.100:/srv/nfs/tegra124 drm.debug=0xf cma=128M

Reverting the patch eliminates the warning. earlyprintk does work fine
for me without this patch.

Thierry

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