linux-kernel - Re: [PATCH] lib/bug: make panic_on_warn available for all architectures

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Date:	Fri, 22 Jan 2016 14:41:47 +0100
From:	Christian Borntraeger <borntraeger@...ibm.com>
To:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Prarit Bhargava <prarit@...hat.com>
Subject: Re: [PATCH] lib/bug: make panic_on_warn available for all
 architectures

On 01/22/2016 02:12 PM, Heiko Carstens wrote:
> Christian Borntraeger reported that panic_on_warn doesn't have any
> effect on s390.
> 
> The panic_on_warn feature was introduced with 9e3961a09798 ("kernel:
> add panic_on_warn"). However it did care only for the case when
> WANT_WARN_ON_SLOWPATH is defined. This is turn is only the case for
> architectures which do not have an own __WARN_TAINT defined.
> 
> Other architectures which do have __WARN_TAINT defined call
> report_bug() for warnings within lib/bug.c which does not call panic()
> in case panic_on_warn is set.
> 
> Let's simply enable the panic_on_warn feature by adding the same code
> like it was added to warn_slowpath_common() in panic.c.
> 
> This enables panic_on_warn also for arm64, parisc, powerpc, s390 and
> sh.
> 
> Cc: Prarit Bhargava <prarit@...hat.com>
> Reported-by: Christian Borntraeger <borntraeger@...ibm.com>
> Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>

Tested-by: Christian Borntraeger <borntraeger@...ibm.com>

> ---
>  lib/bug.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/lib/bug.c b/lib/bug.c
> index cff145f032a5..6cde380f09de 100644
> --- a/lib/bug.c
> +++ b/lib/bug.c
> @@ -175,6 +175,17 @@ enum bug_trap_type report_bug(unsigned long bugaddr, struct pt_regs *regs)
>  			pr_warn("WARNING: at %p [verbose debug info unavailable]\n",
>  				(void *)bugaddr);
> 
> +		if (panic_on_warn) {
> +			/*
> +			 * This thread may hit another WARN() in the panic path.
> +			 * Resetting this prevents additional WARN() from
> +			 * panicking the system on this thread.  Other threads
> +			 * are blocked by the panic_mutex in panic().
> +			 */
> +			panic_on_warn = 0;
> +			panic("panic_on_warn set ...\n");
> +		}
> +
>  		print_modules();
>  		show_regs(regs);
>  		print_oops_end_marker();
>