MIME-Version: 1.0
In-Reply-To: <4FD01896.1010506@intel.com>
References: <4FC2E944.6060903@intel.com>
	<20120604171202.GA8533@x1.osrc.amd.com>
	<1338856360.14538.220.camel@ymzhang.sh.intel.com>
	<20120605081448.GA7097@liondog.tnic>
	<4FCDD72A.9030701@intel.com>
	<4FCDD78A.3070106@intel.com>
	<20120605151542.GA10669@x1.osrc.amd.com>
	<1338942965.14538.233.camel@ymzhang.sh.intel.com>
	<4FCF155B.3090705@intel.com>
	<4FCF160D.8010404@intel.com>
	<20120606152238.GA3874@x1.osrc.amd.com>
	<4FD01896.1010506@intel.com>
Date: Thu, 7 Jun 2012 13:19:16 +0000
Message-ID: <CAO6yerJVKgjHe9LBL1ZfcMUzqHA5iZwSf2La+hf19QBDEQ-L0w@mail.gmail.com>
Subject: Re: [PATCH v7 1/2] printk: add interface for disabling recursion check
From: bing deng <deng8bing@gmail.com>
To: shuox.liu@intel.com
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Yanmin Zhang <yanmin_zhang@linux.intel.com>,
        "Luck, Tony" <tony.luck@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "andi@firstfloor.org" <andi@firstfloor.org>,
        Ingo Molnar <mingo@elte.hu>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8BIT
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 3089
Lines: 88

On Thu, Jun 7, 2012 at 2:57 AM, ShuoX Liu <shuox.liu@intel.com> wrote:
> From: ShuoX Liu <shuox.liu@intel.com>
>
> With some special scenario, such as Machine Check Exception happened
> in printk, we want to bypass printk recursion check to printk some
> important information. So we add these interfaces of printk.
>
> 1) printk_recursion_check_disable() for disabling recursion check
> 2) printk_recursion_check_enable() for enabling recursion check
>
> Signed-off-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
> Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
> ---
> ?include/linux/printk.h | ? ?3 +++
> ?kernel/printk.c ? ? ? ?| ? 17 ++++++++++++++++-
> ?2 files changed, 19 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/printk.h b/include/linux/printk.h
> index 1bec2f7..da48ec7 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -42,6 +42,9 @@ static inline void console_verbose(void)
> ? ? ? ? ? ? ? ?console_loglevel = 15;
> ?}
>
> +void printk_recursion_check_disable(void);
> +void printk_recursion_check_enable(void);
> +
> ?struct va_format {
> ? ? ? ?const char *fmt;
> ? ? ? ?va_list *va;
> diff --git a/kernel/printk.c b/kernel/printk.c
> index 32462d2..0580f67 100644
> --- a/kernel/printk.c
> +++ b/kernel/printk.c
> @@ -78,6 +78,19 @@ int console_printk[4] = {
> ?int oops_in_progress;
> ?EXPORT_SYMBOL(oops_in_progress);
>
> +static atomic_t recursion_check_disabled = ATOMIC_INIT(0);
> +
> +void printk_recursion_check_disable(void)
> +{
> + ? ? ? atomic_inc(&recursion_check_disabled);
> +}
> +
> +void printk_recursion_check_enable(void)
> +{
> + ? ? ? WARN_ON(atomic_read(&recursion_check_disabled) < 1);
> + ? ? ? atomic_dec(&recursion_check_disabled);
> +}
> +
> ?/*
> ?* console_sem protects the console_drivers list, and also
> ?* provides serialisation for access to the entire console
> @@ -1295,7 +1308,9 @@ asmlinkage int vprintk_emit(int facility, int level,
> ? ? ? ? ? ? ? ? * recursion and return - but flag the recursion so that
> ? ? ? ? ? ? ? ? * it can be printed at the next appropriate moment:
> ? ? ? ? ? ? ? ? */
> - ? ? ? ? ? ? ? if (!oops_in_progress && !lockdep_recursing(current)) {
> + ? ? ? ? ? ? ? if (!atomic_read(&recursion_check_disabled)
> + ? ? ? ? ? ? ? ? ? ? ? && !oops_in_progress
> + ? ? ? ? ? ? ? ? ? ? ? && !lockdep_recursing(current)) {
> ? ? ? ? ? ? ? ? ? ? ? ?recursion_bug = 1;
> ? ? ? ? ? ? ? ? ? ? ? ?goto out_restore_irqs;
> ? ? ? ? ? ? ? ?}
> --
> 1.7.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at ?http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at ?http://www.tux.org/lkml/

Hi Shuo,

    Should the two function be export by EXPORT_SYMBOL? The the other
module can use it.

-- 
Best Regards,
Bing
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/