From mboxrd@z Thu Jan  1 00:00:00 1970
From: Julien Grall <julien.grall@linaro.org>
Subject: Re: [PATCH v2 12/15] xen: arm: enable synchronous
 console while starting secondary CPUs
Date: Fri, 22 Nov 2013 17:36:15 +0000
Message-ID: <528F960F.1010300@linaro.org>
References: <foo> <1385137474-31245-12-git-send-email-ian.campbell@citrix.com>
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To: Ian Campbell <ian.campbell@citrix.com>, xen-devel@lists.xen.org
Cc: Keir Fraser <keir@xen.org>, pranavkumar@linaro.org, tim@xen.org, Anup Patel <anup.patel@linaro.org>, stefano.stabellini@eu.citrix.com
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On 11/22/2013 04:24 PM, Ian Campbell wrote:
> Setting synchronous console ensures that any printk hits the buffer
> immediately and that any outstanding queued log messages are flushed. This
> ensures that such log messages are not being printed while the secondary CPU
> may be using early_printk during early bringup.

stefano: There is some place in x86 (shutdown, kexec) when 
console_*_sync are used. So far after console_endboot. I think it's also 
fine for us.

> Signed-of-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: Keir Fraser <keir@xen.org>
> ---
> v2: improved commit message.
> ---
>   xen/arch/arm/smpboot.c |    5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
> index b6a1307..f6cd9d7 100644
> --- a/xen/arch/arm/smpboot.c
> +++ b/xen/arch/arm/smpboot.c
> @@ -28,6 +28,7 @@
>   #include <xen/softirq.h>
>   #include <xen/timer.h>
>   #include <xen/irq.h>
> +#include <xen/console.h>
>   #include <asm/gic.h>
>
>   cpumask_t cpu_online_map;
> @@ -356,6 +357,8 @@ int __cpu_up(unsigned int cpu)
>       if ( rc < 0 )
>           return rc;
>
> +    console_start_sync(); /* Secondary may use early_printk */
> +

I though have asked on the first version this question:

early printk is only enabled when CONFIG_EARLY_PRINTK is defined. Why 
don't you surround console_*_sync with #ifdef CONFIG_EARLY_PRINTK?

-- 
Julien Grall