linux-kernel - Re: [PATCH 2/2] powerpc/mm: check for irq disabled() only if DEBUG

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Date:	Tue, 7 Jun 2016 18:36:17 +1000
From:	Balbir Singh <bsingharora@...il.com>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	akpm@...ux-foundation.org, mpe@...erman.id.au
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] powerpc/mm: check for irq disabled() only if DEBUG_VM
 is enabled.



On 31/05/16 21:04, Aneesh Kumar K.V wrote:
> We don't need to check this always. The idea here is to capture the
> wrong usage of find_linux_pte_or_hugepte and we can do that by
> occasionally running with DEBUG_VM enabled.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/include/asm/pgtable.h | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index ee09e99097f0..9bd87f269d6d 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -71,10 +71,8 @@ pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
>  static inline pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
>  					       bool *is_thp, unsigned *shift)
>  {
> -	if (!arch_irqs_disabled()) {
> -		pr_info("%s called with irq enabled\n", __func__);
> -		dump_stack();
> -	}
> +	VM_WARN(!arch_irqs_disabled(),
> +		"%s called with irq enabled\n", __func__);
>  	return __find_linux_pte_or_hugepte(pgdir, ea, is_thp, shift);
>  }

Agreed! Honestly, I think it should be a VM_BUG_ON() since we have a large reliance
on this elsewhere in the code.

Balbir Singh.