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SubjectRe: [PATCH v5 2/2] x86 mce: use new printk recursion disabling interface
On Tue, Jun 05, 2012 at 05:55:22PM +0800, ShuoX Liu wrote:
> From: ShuoX Liu <shuox.liu@intel.com>
>
> On x86 machines, some times MCE happens just when kernel calls printk
> to output some log info to serial console, while usually MCE module in
> kernel is used to print out some hardware error information, such like
> bad cache or bad memory bank. That causes printk recursion and printk
> would omit MCE printk output.
>
> We hit it when running MTBF testing on Android ATOM mobiles.
>
> Here in mce_panic, we choose to disable printk recursion to make sure
> MCE logs printed out.
>
> Signed-off-by: Yanmin Zhang <yanmin_zhang@linux.intel.com>
> Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
> ---
> arch/x86/kernel/cpu/mcheck/mce.c | 2 ++
> 1 files changed, 2 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 2afcbd2..906e838 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -306,6 +306,7 @@ static void mce_panic(char *msg, struct mce *final, char *exp)
> {
> int i, apei_err = 0;
>
> + printk_recursion_check_disable();
> if (!fake_panic) {
> /*
> * Make sure only one CPU runs in machine check panic
> @@ -360,6 +361,7 @@ static void mce_panic(char *msg, struct mce *final, char *exp)
> panic(msg);
> } else
> pr_emerg(HW_ERR "Fake kernel panic: %s\n", msg);
> + printk_recursion_check_enable();

Ok, let me ask this again: why not disable the printk recursion check in
the function that actually _prints_ the MCE, i.e. print_mce() instead of
here in mce_panic() which does a whole bunch of other stuff and it can
also return without printing any MCE to dmesg?

Are you interested in seeing the printk's from mce_panic? Why?

Thanks.

--
Regards/Gruss,
Boris.


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