linux-kernel - Re: [PATCH v2 1/2] ACPICA: Tables: Fix regression introduced by a too early mechanism enabling

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Date:   Fri, 28 Apr 2017 00:30:38 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Lv Zheng <lv.zheng@...el.com>
Cc:     "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <len.brown@...el.com>, Lv Zheng <zetalog@...il.com>,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v2 1/2] ACPICA: Tables: Fix regression introduced by a too early mechanism enabling

On Thursday, April 27, 2017 04:22:44 PM Lv Zheng wrote:
> In the Linux kernel side, acpi_get_table() clones haven't been fully
> balanced by acpi_put_table() invocations. In ACPICA side, due to the design
> change, there are also unbalanced acpi_get_table_by_index() invocations
> requiring special care to be cleaned up.
> 
> So it is not a good timing to report acpi_get_table() counting errors for
> this period. The strict balanced validation count check should only be
> enabled after confirming that all invocations are safe and compliant to
> their designed purposes.
> 
> Thus this patch removes the fatal error along with lthe error report to
> fix this issue. Reported by Dan Williams, fixed by Lv Zheng.
> 
> Fixes: 174cc7187e6f ("ACPICA: Tables: Back port acpi_get_table_with_size() and early_acpi_os_unmap_memory() from Linux kernel")
> Reported-by: Dan Williams <dan.j.williams@...el.com>
> Signed-off-by: Lv Zheng <lv.zheng@...el.com>

Please do not add #if 0 anywhere to the kernel code base.

If you need to drop some piece of code, just drop it.

And in this particular case validation_count should be dropped from the data
type definition too.

> ---
>  drivers/acpi/acpica/tbutils.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/acpica/tbutils.c b/drivers/acpi/acpica/tbutils.c
> index 5a968a7..8175c70 100644
> --- a/drivers/acpi/acpica/tbutils.c
> +++ b/drivers/acpi/acpica/tbutils.c
> @@ -418,11 +418,13 @@ acpi_tb_get_table(struct acpi_table_desc *table_desc,
>  
>  	table_desc->validation_count++;
>  	if (table_desc->validation_count == 0) {
> +		table_desc->validation_count--;
> +#if 0
>  		ACPI_ERROR((AE_INFO,
>  			    "Table %p, Validation count is zero after increment\n",
>  			    table_desc));
> -		table_desc->validation_count--;
>  		return_ACPI_STATUS(AE_LIMIT);
> +#endif
>  	}
>  
>  	*out_table = table_desc->pointer;
> 

Thanks,
Rafael